Ortho-Phthalaldehyde (OPA)

OPA is an effective choice as a high-level disinfectant for medical devices
Ortho‐phthalaldehyde: a possible alternative to glutaraldehyde for high level disinfection

Ortho-Phthalaldehyde (OPA) has been approved for high-level sterilization of heat-sensitive medical instruments and is increasingly being used as a replacement in the healthcare industry for glutaraldehyde, a known sensitizer.

Ortho-phthalaldehyde is an effective antimicrobial agent and should be the first-choice agent to replace GTA as a high-level disinfectant for endoscopes

Ortho-phthalaldehyde (OPA) is a high-level disinfectant commonly used for processing heat-sensitive medical devices.

In recent years, ortho-phthalaldehyde (OPA) solutions have emerged as alternatives to glutaraldehyde solutions for high-level disinfection of semicritical medical devices.
The increased use of OPA-based disinfection solutions is due in part to the antimicrobial activity of OPA against glutaraldehyde-resistant mycobacteria.
In this chapter we review the available information on the mechanisms of action of OPA against mycobacteria, which are well known for their resistance to many different chemical germicides. The unique cell wall architecture of the mycobacteria, measurements of cell surface hydrophobicity, and resistance to aldehyde-based disinfectants are discussed.

Solutions of glutaraldehyde (GTA) and ortho-phthalaldehyde (OPA) can both be used for low-temperature disinfection of endoscopes.
Currently, GTA is being replaced by OPA (an aromatic dialdehyde), as OPA is less dangerous for health care workers than GTA, but has a similar capacity to kill viruses, bacteria and spores

ortho-Phthalaldehyde
OPA is favored over glutaraldehyde for high-level disinfection in the United States, because it does not require activation, is stable over a wide pH range, does not cause irritation of mucous membranes, and it has a barely perceptible odor.
Its activity is greater than that of glutaraldehyde, and high-level disinfection is achieved with a contact time of 12 minutes at or above 20°C.
The primary disadvantage of OPA is that it stains tissues and mucous membranes gray.
Protective equipment must be worn when handling the solution, and it must be rinsed thoroughly from items after treatment.
Irritation can occur with eye contact.
OPA is also more expensive than glutaraldehyde.
Solutions can be reused for a maximum of 14 days.

As an alternative to the sterilant glutaraldehyde, products containing the less high-level disinfectant ortho-phthalaldehyde are thought to be safer, having similar disinfectant properties with less health risks to repurposing personnel due to its lower vapor pressure and lower toxicity levels.

A reagent that forms fluorescent conjugation products with primary amines. It is used for the detection of many biogenic amines, peptides, and proteins in nanogram quantities in body fluids.

Phthalaldehyde is a dialdehyde in which two formyl groups are attached to adjacent carbon centres on a benzene ring.
It has a role as an epitope.
It is a dialdehyde and a member of benzaldehydes.

Phthalaldehyde is used as a disinfectant and as a tanning agent in leather industry.
It is useful for the sterilization of endoscopic instruments, thermometers, rubber and plastic equipment which cannot be sterilized by heating system.

It is also used as an intermediate in synthesis of pharmaceuticals, medicines, and other organic compounds.
In chemical sterilant field, phthalaldehyde, compare with glutaraldehyde, is not irritant to the eyes and nasal passages but has excellent stability over a wide range of pH (3-9), which does not require exposure monitoring, and has a barely perceptible odor.
But phthaldialdehyde stains proteins gray including unprotected skin.
Thus, it must be handled with use of gloves, eye protection, fluid-resistant gowns when handling contaminated instruments, contaminated equipment, and chemicals.

Ortho-phthalaldehyde: a possible alternative to glutaraldehyde for high level disinfection

Abstract
Ortho-phthalaldehyde (OPA) was tested against a range of organisms including glutaraldehyde-resistant mycobacteria, Bacillus subtilis spores and coat-defective spores.
Glutaraldehyde (GTA) and peracetic acid (PAA) were tested for comparative purposes.
Both suspension and carrier tests were performed using a range of concentrations and exposure times.
All three biocides were very effective (> or = 5 log reduction) against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa in suspension tests.
OPA and GTA (PAA was not tested) were also very effective against Staph. aureus and Ps. aeruginosa in carrier tests.
OPA showed good activity against the mycobacteria tested including the two GTA-resistant strains, but 0.5% w/v OPA was found not to be sporicidal.
However, limited activity was found with higher concentrations and pH values.
Coat-defective spores were more susceptible to OPA, suggesting that the coat may be responsible for this resistance.
The findings of this study suggest that OPA is effective against GTA-resistant mycobacteria and that it is a viable alternative to GTA for high level disinfection.

OPA (ortho-phthalaldehyde) is marketed as a safer alternative to glutaraldehyde for endoscope decontamination

Phthalaldehyde (sometimes also o-phthalaldehyde or ortho-phthalaldehyde, OPA) is the chemical compound with the formula C6H4(CHO)2.
It is one of three isomers of benzene dicarbaldehyde, related to phthalic acid.
This pale yellow solid is a building block in the synthesis of heterocyclic compounds and a reagent in the analysis of amino acids.
OPA dissolves in water solution at pH < 11.5. Its solutions degrade upon UV illumination and exposure to air.

Ortho-phthalaldehyde

Since its introduction in 1999, ortho-phthalaldehyde (OPA) has been accepted as a better, safer alternative to glutaraldehyde in most US healthcare facilities.
Cidex OPA by Advanced Sterilization Products (a Johnson & Johnson company) was cleared by the US FDA as a high-level disinfectant and emerged as a suitable replacement of glutaraldehyde for the disinfection of endoscopes.

OPA has excellent microbiocidal activity and superior mycobactericidal activity compared with glutaraldehyde, and has potent bactericidal and sporicidal activity.
Like glutaraldehyde, it interacts with amino acids, proteins and microorganisms.

OPA has many advantages over glutaraldehyde, such as improved stability at varying pH ranges, lower inhalation exposure risk and a wider range of material compatibility, although it costs almost three times more; but, considering the cost of the sophisticated ventilation systems needed to minimise the respiratory hazards of using glutaraldehyde, OPA is more economical.

The mycobactericidal efficacy of ortho-phthalaldehyde and the comparative resistances of Mycobacterium bovis, Mycobacterium terrae, and Mycobacterium chelonae
A W Gregory 1, G B Schaalje, J D Smart, R A Robison
Affiliations expand
PMID: 10349948 DOI: 10.1086/501625
Abstract
Objectives: To assess the mycobactericidal efficacy of an agent relatively new to disinfection, ortho-phthalaldehyde (OPA) and to compare the resistances of three Mycobacterium species.
Mycobacterium bovis (strain BCG) was compared with Mycobacterium chelonae and Mycobacterium terrae to investigate the feasibility of using either of the latter two species in tuberculocidal testing. M. chelonae (a rapid grower) and M. terrae (an intermediate grower) both grow faster and are less virulent than M. bovis (a slow grower).

Design: The quantitative suspension protocol specified by the Environmental Protection Agency (EPA), the Tuberculocidal Activity Test Method (EPA test), was used throughout this study. Standard suspensions of all three species were prepared in a similar manner.
Two suspensions of M. bovis, created in different laboratories, were used.
These were tested against two concentrations of alkaline glutaraldehyde to provide reference data.
Two concentrations of OPA were evaluated against all mycobacterial test suspensions. Four replicates of each organism-disinfectant combination were performed.

Results: Results were assessed by analysis of variance. M. terrae was significantly more resistant to 0.05% OPA than either M. bovis or M. chelonae.
At 0.21% OPA, M. terrae was slightly more susceptible than one test suspension of M. bovis, but not significantly different from the other. M. chelonae was significantly less resistant than the other species at both OPA concentrations.
At their respective minimum effective concentration, OPA achieved a 6-log10 reduction of M. bovis in nearly one sixth the time required by glutaraldehyde (5.5 minutes vs. 32 minutes).

Conclusions: These data, along with other recent studies, lend support to the idea that M. terrae may be a suitable test organism for use in the tuberculocidal efficacy testing of disinfectants. They also confirm the relatively rapid tuberculocidal activity of OPA.

The compound was first described in 1887 when it was prepared from α,α,α’,α’-tetrachloro-ortho-xylene.
A more modern synthesis is similar: the hydrolysis of the related tetrabromo-o-xylene using potassium oxalate, followed by purification by steam distillation.

The reactivity of OPA is complicated by the fact that in water it forms both a mono- and dihydrate, C6H4(CHO)(CH(OH)2) and C6H4(CH(OH))2O, respectively.
Its reactions with nucleophiles often involves the reaction of both carbonyl groups

OPA is used in a very sensitive fluorescent reagent for assaying amines or sulfhydryls in solution, notably contained in proteins, peptides, and amino acids, by capillary electrophoresis and chromatography.
OPA reacts specifically with primary amines above their isoelectric point Pi in presence of thiols.
OPA reacts also with thiols in presence of an amine such as n-propylamine or 2-aminoethanol.
The method is spectrometric (fluorescent emission at 436-475 nm (max 455 nm) with excitation at 330-390 nm (max. 340 nm))

Disinfection
OPA is commonly used as a high-level disinfectant for medical instruments, commonly sold under the brand names of Cidex OPA or TD-8.
Disinfection with OPA is indicated for semi-critical instruments that come into contact with mucous membranes or broken skin, such as specula, laryngeal mirrors, and internal ultrasound probes

OPA can be polymerized.
In the polymer, one of the oxygen atoms forms a bridge to the other non-ring carbon of the same phthalaldehyde unit, while the other bridges to a non-ring carbon of another phthalaldehyde unit. Poly(phthalaldehyde) is used in making a photoresist

In winemaking
The Nitrogen by O-Phthaldialdehyde Assay (NOPA) is one of the methods used in winemaking to measure yeast assimilable nitrogen (or YAN) needed by wine yeast in order to successfully complete fermentation

IUPAC name: Phthalaldehyde
Preferred IUPAC name
Benzene-1,2-dicarbaldehyde

Other names
Benzene-1,2-dicarboxaldehyde
o-Phthalaldehyde
o-Phthalic dicarboxaldehyde
Phthaldialdehyde
Phtharal
Phthalaldehyde

Other Names
1,2-Diformylbenzene
NSC 13394
Phthalaldehyde
Phthalaldialdehyde
Phthaldialdehyde
Phthalic aldehyde
Phthalic dialdehyde
Phthalic dicarboxaldehyde
Phthalyldicarboxaldehyde
o-Phthalaldehyde
o-Phthaldehyde
o-Phthaldialdehyde
o-Phthalicdicarboxaldehyde

Disinfection, Sterilization, and Control of Hospital Waste
William A. Rutala, David J. Weber, in Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases (Eighth Edition), 2015
Ortho-phthalaldehyde
Ortho-phthalaldehyde (OPA) is a high-level disinfectant that received FDA clearance in October 1999.
It contains at least 0.55% 1,2-benzenedicarboxaldehyde or OPA, and it has supplanted glutaraldehyde as the most commonly used “aldehyde” for high-level disinfection in the United States.
OPA solution is a clear, pale-blue liquid with a pH of 7.5.
The advantages, disadvantages, and characteristics of OPA are listed in Table 301-2.
Studies have demonstrated excellent microbicidal activity in in vitro studies, including superior mycobactericidal activity (5-log10 reduction in 5 minutes) compared with glutaraldehyde.
Walsh and colleagues also found OPA effective (>5-log10 reduction) against a wide range of microorganisms, including glutaraldehyde-resistant mycobacteria and Bacillus atrophaeus spores.150
OPA has several potential advantages compared with glutaraldehyde.
It has excellent stability over a wide pH range (pH 3 to 9), is not a known irritant to the eyes and nasal passages, does not require exposure monitoring, has a barely perceptible odor, and requires no activation.
OPA, like glutaraldehyde, has excellent material compatibility.
A potential disadvantage of OPA is that it stains proteins gray (including unprotected skin) and thus must be handled with caution.
However, skin staining would indicate improper handling that requires additional training and/or personal protective equipment (gloves, eye and mouth protection, fluid-resistant gowns).
OPA residues remaining on inadequately water-rinsed transesophageal echocardiographic probes may leave stains on the patient’s mouth.
Meticulous cleaning, use of the correct OPA exposure time (e.g., 12 minutes), and copious rinsing of the probe with water should eliminate this problem.
Because OPA has been associated with several episodes of anaphylaxis after cystoscopy, the manufacturer has modified its instructions for use of OPA and contraindicates the use of OPA as a disinfectant for reprocessing all urologic instrumentation for patients with a history of bladder cancer.
Personal protective equipment should be worn when handling contaminated instruments, equipment, and chemicals.
In addition, equipment must be thoroughly rinsed to prevent discoloration of a patient’s skin or mucous membrane.
The MEC of OPA is 0.3%, and that concentration is monitored by test strips designed specifically for the OPA solution.
OPA exposure level monitoring found that the concentration during the disinfection process was significantly higher in the manual group (median, 1.43 ppb) than in the automatic group (median, 0.35 ppb).
These findings corroborate other findings that show it is desirable to introduce automatic endoscope reprocessors to decrease disinfectant exposure levels among scope reprocessing technicians

Ortho‐phthalaldehyde: a possible alternative to glutaraldehyde for high level disinfection !!!
Ortho‐phthalaldehyde (OPA) was tested against a range of organisms including glutaraldehyde‐resistant mycobacteria, Bacillus subtilis spores and coat‐defective spores.
Glutaraldehyde (glutaraldehyde) and peracetic acid (PAA) were tested for comparative purposes.
Both suspension and carrier tests were performed using a range of concentrations and exposure times.
All three biocides were very effective (≥ 5 log reduction) against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa in suspension tests.
OPA and glutaraldehyde (PAA was not tested) were also very effective against Staph. aureus and Ps. aeruginosa in carrier tests.
OPA showed good activity against the mycobacteria tested including the two glutaraldehyde‐resistant strains, but 0·5% w/v OPA was found not to be sporicidal.
However, limited activity was found with higher concentrations and pH values.
Coat‐defective spores were more susceptible to OPA, suggesting that the coat may be responsible for this resistance.
The findings of this study suggest that OPA is effective against glutaraldehyde‐resistant mycobacteria and that it is a viable alternative to glutaraldehyde for high level disinfection.

INTRODUCTION

Glutaraldehyde (glutaraldehyde) has been used as a disinfecting/ sterilizing agent for over 30 years.
Alkaline glutaraldehyde (2% v/v) has a broad range of activity and rapid antimicrobial action as well being non‐corrosive to metals, rubber and lenses.
However, potential mutagenic and carcinogenic effects have been reported as well as skin and eye irritation and respiratory disorders.
The risk to personnel and the increasing frequency of glutaraldehyde‐resistant Mycobacterium chelonae has highlighted the need for a replacement.

One possible alternative to glutaraldehyde is ortho‐phthalaldehyde (OPA).
OPA is already used in amino acid analysis but 0·5% (w/v) OPA has also been demonstrated to be bactericidal.
When assessed in the disinfection of 100 endoscopes, OPA was found to be effective without activation and was stable over a 14‐day usage cycle.
Mycobactericidal activity has also been demonstrated against M. bovis with a 5 log reduction after 5 min exposure to 0·2% OPA.

Another possible glutaraldehyde alternative is peracetic acid (PAA).
PAA was introduced as an antibacterial agent in 1955; it has a broad spectrum of activity including bacteria, spores, moulds, yeasts, algae and viruses.
PAA is a powerful oxidizing agent and can be corrosive to some metals.
However, corrosive problems can be reduced by using commercial formulations and 13 months usage of PAA gave no overtly visible signs of corrosion of flexible endoscopes using the Steris system.
‘Nu‐Cidex’, an equilibrium mixture of acetic acid, PAA, and hydrogen peroxide has been shown to be rapidly mycobactericidal, including against drug‐resistant isolates of Mycobacterium tuberculosis and M. avium‐intracellulare, after only 5 min.

This study was initiated to investigate the biocidal properties of OPA against a range of non‐acid‐fast non‐sporulating organisms, glutaraldehyde‐sensitive and resistant mycobacteria and B. subtilis spores.
A suspension test and a carrier test were used to evaluate the activity of the biocides; this was considered necessary as it has been shown that disinfectants with high activity in suspension tests are not necessarily as active on contaminated surfaces.
Spores treated with urea/dithiothreitol/sodium lauryl sulphate (UDS), pH 10·3, were also used.
The removal of protein from the spore coat has been shown to dramatically increase the sensitivity of B. subtilis to alkaline glutaraldehyde and the same effect was thought likely to occur with OPA.
Comparisons with glutaraldehyde and PAA were carried out to assess OPA activity.
Discussion
Despite the high number of bacteria needed to measure large log reductions in these experiments, all three biocides tested were shown to be very effective against non‐acid‐fast nonsporulating organisms.
OPA, like the other two biocides, was still very effective at concentrations far lower than its recommended in‐use concentration of 0·5% (w/v) and was equally effective against both the Gram‐negative and Gram‐positive test bacteria.

Due to the increase in the number of organisms tested, a direct comparison between the results of the suspension tests and carrier tests could not be drawn.
However, both concentrations of OPA and glutaraldehyde were still effective (≥ 5 log reduction) with only 10 min of exposure time against both of the test organisms, and the recommended in‐use concentrations of 0·5% (w/v) and 2% (v/v) for OPA and glutaraldehyde, respectively, were effective within 2 min.
Therefore, it can be concluded that drying of these test organisms did not significantly impair the action of either OPA or glutaraldehyde despite the increased cell numbers.

Due to the worrying increase in isolation of glutaraldehyde‐resistant M. chelonae from washer disinfectors and processed endoscopes, it was encouraging to note a lack of cross‐resistance to OPA in the two glutaraldehyde‐resistant washer isolates tested. OPA (0·5 w/v) and 2% (v/v) alkaline glutaraldehyde were also very effective against M. terrae NCTC 10856, which has been suggested as a possible surrogate testing organism for M. tuberculosis, although M. avium‐intracellulare was found to be more resistant.
The other two M. chelonae strains tested were sensitive to both biocides, although glutaraldehyde was slightly more effective against M. chelonae var. abscessus.
The rapid action of glutaraldehyde against M. chelonae NCTC 946 was confirmed with a ≥ 6 log reduction within 1 min of exposure.

The sporicidal activity of glutaraldehyde was confirmed with the same 3 h exposure time found in other studies.
The lack of any sporicidal effect with 0·5% (w/v) OPA seemed to be connected with the spore coat as there was a large increase in activity when coat‐defective (UDS‐treated) spores were tested.
Raising the pH of OPA to 8 increased its efficacy but not to the levels seen with 2% (v/v) alkaline glutaraldehyde.
Increasing the concentration of the OPA as well as the pH did produce sporicidal activity, although OPA took longer (preparation of 2% w/v OPA was aided by warming) to dissolve at these higher concentrations.

In conclusion, 0·5% (w/v) OPA is considered to be a viable alternative to glutaraldehyde for high level disinfection where, by definition, the compound need not have a lethal action against high levels of bacterial spores.
OPA should not be used in situations where sterilization is required, but it might be particularly useful in washer systems where glutaraldehyde‐resistant organisms have developed.

Acknowledgements
The authors thank Prof. S.A. Sattar and Dr V.S. Springthorpe of the Department of Microbiology and Immunology, School of Medicine, University of Ottawa, for their help with the carrier test design. They are also grateful for the financial support of Johnson & Johnson, USA, in providing a research studentship (to S.E.W.).

Comparison between Glutaraldehyde and Ortho-Phthalaldehyde Air Levels during Endoscopic Procedures
Author links open overlay panelC.Marena∗L.LodolaR.LodiL.Zambianchi

Abstract
BACKGROUND: Glutaraldehyde (glutaraldehyde) has been used as a disinfecting agent for over 30 years, but irritative effects on the skin and respiratory tract have been described.
The risk to healthcare personnel and emerging of glutaraldehyde-resistant microorganisms have highlighted the need to develop new agents.
One possible alternative to glutaraldehyde is ortho-phthalaldehyde (OPA), which has a similar capacity to kill bacteria and a very good toxicological profile.

OBJECTIVE: To compare air levels of glutaraldehyde and OPA during high-level disinfection of endoscopes.

METHODS: The comparative study was carried out in ten endoscopy units of the San Matteo Hospital, where glutaraldehyde and OPA were routinely used for the low-temperature disinfection of endoscopes.
glutaraldehyde and OPA were used under the same operating procedures and for the same exposure time (4 hours).
The monitoring of air levels was performed with both HPLC-UV (High Performance Liquid Chromatography with UV detection) and Infrared Spectroscopy (IR).

RESULTS: The HPLC method gave a much lower aldheyde value when using OPA (8.4 mg/m3) compared to that obtained when glutaraldehyde was used to disinfect endoscopes (21279.3 mg/m3).
These results were confirmed with IR detection method (the mean values being below 10 mg/m3).
In addition, we studied the resistance of various glove types to OPA.
Tests showed that OPA-permeated vinyl gloves more rapidly (26628 ng/cm2 per hour) than nitrile gloves (13.9 ng/cm2 per hour).

CONCLUSION: This study showed a very low air concentration of OPA compared to glutaraldehyde.
These findings confirm the excellent safety profile of OPA used as a high-level disinfectant in the hospital setting.

Ortho-Phthalaldehyde (OPA) is an aromatic dialdehyde, used as a high-level antimicrobial disinfectant for medical equipment which is sensitive to normal heat or steam sterilization processes, including endoscope, cystoscopes, and certain dental instruments.
For 40 years, glutaraldehyde, another dialdehyde, has been the primary choice for disinfecting heat-sensitive medical devices; however, it has been reported to be a chemical sensitizer.
Glutaraldehyde is known to have high affinity for biological amines, and its use as a tissue fixative capitalizes on this property.
As such, glutaraldehyde and dialdehydes as a chemical class can bind to native proteins, thus, altering their presentation to the immune system.
Haptenization of native proteins can lead to an aberrant immune response and the development of allergy.
Several human studies have demonstrated the presence of IgE antibodies specific for glutaraldehyde adducts in the serum of exposed workers with respiratory disease.
Importantly, workplace exposure to glutaraldehyde is known to induce occupational asthma ] and allergic contact dermatitis suggesting the need for safer alternatives.
OPA has shown superior antimycobactericidal activity as compared to glutaraldehyde, allowing for its use at lower concentrations.
In addition, low volatility and no need for activation have increased the use of OPA as a more practical alternative to glutaraldehyde.

Cas no: 643-79-8;PHTHALALDEHYDE;PHTHARAL; o-Phthaldialdehyde; Benzene-1,2-dicarboxaldehyde; 1,2-Benzenedicarboxaldehyde; Phthaldialdehyde; Phthalic aldehyde; Phthalic dialdehyde; ortho-Phthalaldehyde; Phthalyldicarboxaldehyde; o-Phthaldehyde; benzene-1,2-dicarbaldehyde; Phthalic dicarboxaldehyde; Phthalaldialdehyde
;o-Phthalicdicarboxaldehyde; 1,2-Diformylbenzene; 2-PHTHALALDEHYDE

In chemical sterilant field, phthalaldehyde, compare with glutaraldehyde, is not irritant to the eyes and nasal passages but has excellent stability over a wide range of pH (3-9), which does not require exposure monitoring, and has a barely perceptible odor.
But phthaldialdehyde stains proteins gray including unprotected skin. Thus, it must be handled with use of gloves, eye protection, fluid-resistant gowns when handling contaminated instruments, contaminated equipment, and chemicals.
Pure ortho-phthalaldehyde is rarely encountered.
When used as a disinfectant, it comes in the form of an aqueous solution with a concentration of approximately 0.55%.
Commercial solutions contain additives that help stabilize their pH, such as citric acid and phosphates, preservatives and colorants.

Use and sources of emission:
Ortho-phthalaldehyde is primarily used as a high-efficiency chemical disinfectant for dental or medical instruments, such as endoscopes.
It is often considered a safer alternative to glutaraldehyde.

It is also used in the laboratory, as a reagent for fluorometric analyzes of primary amines and thiols.

Phthalaldehyde (sometimes also o-phthalaldehyde or ortho-phthalaldehyde, OPA) is the chemical compound with the formula C6H4(CHO)2.
It is one of three isomers of benzene dicarbaldehyde, related to phthalic acid.
This pale yellow solid is a building block in the synthesis of heterocyclic compounds and a reagent in the analysis of amino acids.
OPA dissolves in water solution at pH < 11.5.
Its solutions degrade upon UV illumination and exposure to air.

o-PHTHALALDEHYDE
PRODUCT IDENTIFICATION
CAS NO. 643-79-8
o-PHTHALALDEHYDE

EINECS NO.: 211-402-2
FORMULA: C6H4-1,2-(CHO)2
MOL WT.: 134.12

SYNONYMS: 1,2-Benzenedicarboxaldehyde; 2-Formylbenzaldehyde;1,2-Benzenedialdehyde; 1,2-Phthalic Dicarboxyaldehyde; OPA; PA; Phtalaldehydes (French);
PHYSICAL AND CHEMICAL PROPERTIES

PHYSICAL STATE: Light yellow crystalline powder
MELTING POINT: 56 C

Health: 2 ; Flammability: 1 ; Reactivity: 0
REFRACTIVE INDEX

o-Phthalaldehyde Properties
Melting point:55-58 °C(lit.)
Boiling point:83-84 °C (0.7501 mmHg)
Density 1.13
refractive index 1.4500 (estimate)
Flash point:>230 °F
storage temp. 2-8°C
solubility The solubility of o-phthalaldehyde is 3g/100 mL diisopropyl ether, 5g/100mL deionized water, 20g/100mL chloroform, or 20g/100mL acetone at 20°C.
form:powder
color: yellow
Stability:Stable. Air sensitive. Incompatible with strong oxidizing agents, strong bases.
NIST Chemistry Reference: O-phthalaldehyde(643-79-8)
EPA Substance Registry System: 1,2-Benzenedicarboxaldehyde (643-79-8)

FLASH POINT: 110 C

STABILITY: Stable under ordinary conditions

APPLICATIONS
Phthalaldehyde is used as a disinfectant and as a tanning agent in leather industry.
It is useful for the sterilization of endoscopic instruments, thermometers, rubber and plastic equipment which cannot be sterilized by heating system.
It is also used as an intermediate in synthesis of pharmaceuticals, medicines, and other organic compounds.

SALES SPECIFICATION
APPEARANCE

Light yellow crystalline powder
PURITY: 99.0% min
INDIVIDUAL IMPURITY: 0.5% max
WATER: 0.5% max
HAZARD CLASS: 8
UN NO.: 1759
REMARKS: In chemical sterilant field, phthalaldehyde, compare with glutaraldehyde, is not irritant to the eyes and nasal passages but has excellent stability over a wide range of pH (3-9), which does not require exposure monitoring, and has a barely perceptible odor. But phthaldialdehyde stains proteins gray including unprotected skin. Thus, it must be handled with use of gloves, eye protection, fluid-resistant gowns when handling contaminated instruments, contaminated equipment, and chemicals.

YELLOW SOLID IN VARIOUS FORMS WITH CHARACTERISTIC ODOUR.

Synthesis and reactions
The compound was first described in 1887 when it was prepared from α,α,α’,α’-tetrachloro-ortho-xylene.
A more modern synthesis is similar: the hydrolysis of the related tetrabromoxylene using potassium oxalate, followed by purification by steam distillation.

Biochemistry
OPA is used in a very sensitive fluorescent reagent for assaying amines or sulfhydryls in solution, notably contained in proteins, peptides, and amino acids, by capillary electrophoresis and chromatography.
OPA reacts specifically with primary amines above their isoelectric point Pi in presence of thiols.
OPA reacts also with thiols in presence of an amine such as n-propylamine or 2-aminoethanol.
The method is spectrometric (fluorescent emission at 436-475 nm (max 455 nm) with excitation at 330-390 nm (max. 340 nm)).
O-Phthalaldehyde (OPA) is a chemical reagent that forms fluorescent conjugation products with primary amines.
It is used for the detection of many biogenic amines, peptides, and proteins in nanogram quantities in body fluids.
O-Phthalaldehyde is approved by FDA for use in test systems to detect blood urea nitrogen (BUN) for the diagnosis and treatment of certain renal and metabolic diseases.
OPA is also a known desinfectant and has been approved for high-level sterilization of heat-sensitive medical instruments and is increasingly being used as a replacement in the healthcare industry for glutaraldehyde.
OPA has also been approved for use as an indoor antimicrobial pesticide; an intermediate for the synthesis of pharmaceuticals, medicines, and other organic compounds.

Poly(phthalaldehyde)
OPA can be polymerized. In the polymer, one of the oxygen atoms forms a bridge to the other non-ring carbon of the same phthalaldehyde unit, while the other bridges to a non-ring carbon of another phthalaldehyde unit.
Poly(phthalaldehyde) is used in making a photoresist.

Ortho-phthalaldehyde (OPA) is a high-level disinfectant that received FDA clearance in October 1999.
It contains at least 0.55% 1,2-benzenedicarboxaldehyde or OPA, and it has supplanted glutaraldehyde as the most commonly used “aldehyde” for high-level disinfection in the United States.
OPA solution is a clear, pale-blue liquid with a pH of 7.5.
The advantages, disadvantages, and characteristics of OPA are listed in Table 301-2.

Studies have demonstrated excellent microbicidal activity in in vitro studies,74,75,93,111,147-152 including superior mycobactericidal activity (5-log10 reduction in 5 minutes) compared with glutaraldehyde.
Walsh and colleagues also found OPA effective (>5-log10 reduction) against a wide range of microorganisms, including glutaraldehyde-resistant mycobacteria and Bacillus atrophaeus spores.

OPA has several potential advantages compared with glutaraldehyde.
It has excellent stability over a wide pH range (pH 3 to 9), is not a known irritant to the eyes and nasal passages, does not require exposure monitoring, has a barely perceptible odor, and requires no activation.
OPA, like glutaraldehyde, has excellent material compatibility.
A potential disadvantage of OPA is that it stains proteins gray (including unprotected skin) and thus must be handled with caution.
However, skin staining would indicate improper handling that requires additional training and/or personal protective equipment (gloves, eye and mouth protection, fluid-resistant gowns).
OPA residues remaining on inadequately water-rinsed transesophageal echocardiographic probes may leave stains on the patient’s mouth.
Meticulous cleaning, use of the correct OPA exposure time (e.g., 12 minutes), and copious rinsing of the probe with water should eliminate this problem.
Because OPA has been associated with several episodes of anaphylaxis after cystoscopy, the manufacturer has modified its instructions for use of OPA and contraindicates the use of OPA as a disinfectant for reprocessing all urologic instrumentation for patients with a history of bladder cancer.
Personal protective equipment should be worn when handling contaminated instruments, equipment, and chemicals.
In addition, equipment must be thoroughly rinsed to prevent discoloration of a patient’s skin or mucous membrane.
The MEC of OPA is 0.3%, and that concentration is monitored by test strips designed specifically for the OPA solution.
OPA exposure level monitoring found that the concentration during the disinfection process was significantly higher in the manual group (median, 1.43 ppb) than in the automatic group (median, 0.35 ppb).
These findings corroborate other findings that show it is desirable to introduce automatic endoscope reprocessors to decrease disinfectant exposure levels among scope reprocessing technicians

Isomeric phthalaldehydes
Related to phthalaldehyde are:

isophthalaldehyde (benzene-1,3-dicarbaldehyde; m.p. 87–88 °C, CAS# 626-19-7)
terephthalaldehyde (benzene-1,4-dicarbaldehyde; m.p. 114–116 °C, CAS# 623-27-8)

IUPAC name: Phthalaldehyde
Preferred IUPAC name: Benzene-1,2-dicarbaldehyde
Other names: Benzene-1,2-dicarboxaldehyde; o-Phthalaldehyde; o-Phthalic dicarboxaldehyde; Phthaldialdehyde
CAS Number: 643-79-8
CHEBI:70851
ChemSpider: 4642
ECHA InfoCard 100.010.367

Properties
Chemical formula: C8H6O2
Molar mass: 134.134 g·mol−1
Appearance:Yellow solid
Density:1.19 g/mL
Melting point: 55.5 to 56 °C (131.9 to 132.8 °F; 328.6 to 329.1 K)
Boiling point: 266.1 °C (511.0 °F; 539.2 K)
Solubility in water: Low
Hazards
Main hazards: Toxic, Irritant
R-phrases (outdated): R25 R34 R43 R50
S-phrases (outdated): S26 S36/37/39

o-Phthalaldehyde, vapor fraction

Phthalaldehyde.IUPAC names: 1,2-Benzenedicarboxaldehyde;o-Phthalaldehyde;o-Phthalaldehyde;Phthaldialdehyd;o-Phthalaldehyde;o-Phthaldialdehyde;643-79-8

Aldehyde, ortho-Phthalico Phthalaldehydeo Phthaldialdehydeo-Phthalaldehydeo-Phthaldialdehydeortho Phthalaldehydeortho Phthalic Aldehydeortho-Phthalaldehydeortho-Phthalic AldehydeOrthophthaldialdehyde

benzene-1,2-dicarbaldehyde

o-Phthalaldehyde [for HPLC Labeling]

o-Phthalaldehyde
Cas no: 643-79-8
PHTHALALDEHYDE;PHTHARAL; o-Phthaldialdehyde; Benzene-1,2-dicarboxaldehyde; 1,2-Benzenedicarboxaldehyde; Phthaldialdehyde; Phthalic aldehyde; Phthalic dialdehyde; ortho-Phthalaldehyde; Phthalyldicarboxaldehyde; o-Phthaldehyde; benzene-1,2-dicarbaldehyde; Phthalic dicarboxaldehyde; Phthalaldialdehyde
;o-Phthalicdicarboxaldehyde; 1,2-Diformylbenzene; 2-PHTHALALDEHYDE

O-PHTHALALDEHYDE
PHTHARAL
O-PHTHALDIALDEHYDE
1,2-BENZENEDICARBOXALDEHYDE
1,2-Phthalic dicarboxaldehyde
ortho Phthalaldehyde
o-Phthalic dicarboxaldehyde
1,2-BENZENEDICARBALDEHYDE
OPA
OPTA
Phtalaldehydes [French]
2-PHTHALDIALDEHYDE
EINECS 211-402-2
Phtalaldehydes
1,2-Phthalic dicarboxaldehyde, 98+%
CAS-643-79-8
Orthophthaldialdehyde
ortho-Phthalic Aldehyde
phthalaldehyd
o-Phthalaldehyd
o-phthal aldehyde
orthophthalaldehyde
Phtharal (JAN)
Disopa (TN)
2-PHTHALDEHYDE
Phthaldialdehyde Reagent
PubChem17402
ORTHO-PHTHALADEHYDE
phthalaldehyde;Phthalaldehyde
O-PHTHALIC DIALDEHYDE
2-Phthaldehyde, High purity
Benzene-1,2-dicarboxakdehyde
1,2-Benzenedialdehyde;Phthalaldehyde
FLUORALDEHYDE(TM) O-PHTHALALDEHYDE
Phthaldialdehyde Reagent, Solution Complete
Phthaldialdehyde Reagent, Solution Incomplete
Phthaldialdehyde, for fluorescence, >=99.0% (HPLC)
6-Oxomethylene-5-[(E)-hydroxymethylene]cyclohexa-1,3-diene
6-Oxomethylene-5-[(Z)-hydroxymethylene]cyclohexa-1,3-diene
Phthaldialdehyde, >=97% (HPLC), powder (may contain lumps)
Phthaldialdehyde, suitable for HPLC fluorimetric detection of amino acids, >=99% (HPLC), powder

ortho-Phthalaldehyde
1,2-Benzenedicarboxaldehyde [ACD/Index Name]
211-402-2 [EINECS]
4-07-00-02138 (Beilstein Handbook Reference) [Beilstein]
643-79-8 [RN]
Benzene-1,2-dicarbaldehyde [ACD/IUPAC Name]
Benzene-1,2-dicarboxaldehyde [ACD/IUPAC Name]
Benzol-1,2-dicarbaldehyd [German]
o-Phthalaldehyde
o-Phthaldialdehyde
Phtalaldéhyde [French] [ACD/IUPAC Name]
Phthalaldehyd [German] [ACD/IUPAC Name]
Phthalaldehyde [ACD/IUPAC Name]
Phthaldialdehyde
VHR BVH [WLN]
[643-79-8]
o-phthalaldehyde
o-phthaldialdehyde
o-phthalicdicarboxaldehyde
1,2-Diformylbenzene
4P8QP9768A
68234-47-9 [RN]
BR-44048
CHEBI 70851
D03470
Disopa
Disopa (TN)
MFCD00003335 [MDL number]
NCGC00166206-01
OPA
OPTA
P-6600
Phtalaldehydes [French]
Phthalic dicarboxaldehyde
Phthalyldicarboxaldehyde
Phtharal
Phtharal (JAN)
SBB008450
SS-7380
STR01056
TH6950000 [RTECS]
UNII-4P8QP9768A
オルトフタルアルデヒド [Japanese]

IUPAC Name
benzene-1,2-dicarbaldehyde
Synonyms
1,2-Benzenedicarboxaldehyde
1,2-Diformylbenzene
o-phthalaldehyde
o-Phthaldehyde
o-Phthaldialdehyde
o-Phthaldialdehyde
o-Phthalicdicarboxaldehyde
OPA ChEBI
OPTA ChEBI
Phthalaldialdehyde
Phthaldialdehyde
Phthalic aldehyde
Phthalic dialdehyde
Phthalic dicarboxaldehyde
Phthalyldicarboxaldehyde
OPA;OPD;o-PhthaL;Phtharal;CIDEX-OPA;phthaldehyde;PHTHALALDEHYDE;2-PHTHALDEHYDE;Phthaldialdehy;phtalaldehydes

O-Phthalaldehyde (OPA) is a chemical reagent that forms fluorescent conjugation products with primary amines.
It is used for the detection of many biogenic amines, peptides, and proteins in nanogram quantities in body fluids.
O-Phthalaldehyde is approved by FDA for use in test systems to detect blood urea nitrogen (BUN) for the diagnosis and treatment of certain renal and metabolic diseases.
OPA is also a known desinfectant and has been approved for high-level sterilization of heat-sensitive medical instruments and is increasingly being used as a replacement in the healthcare industry for glutaraldehyde.
OPA has also been approved for use as an indoor antimicrobial pesticide; an intermediate for the synthesis of pharmaceuticals, medicines, and other organic compounds..

o-Phthalaldehyde – Science topic
A reagent that forms fluorescent conjugation products with primary amines.
It is used for the detection of many biogenic amines, peptides, and proteins in nanogram quantities in body fluids.

ortho-Phthalaldehyde
1,2-Benzenedicarboxaldehyde [ACD/Index Name]
211-402-2 [EINECS]
4-07-00-02138 (Beilstein Handbook Reference) [Beilstein]
643-79-8 [RN]
Benzene-1,2-dicarbaldehyde [ACD/IUPAC Name]
Benzene-1,2-dicarboxaldehyde [ACD/IUPAC Name]
Benzol-1,2-dicarbaldehyd [German]
o-Phthalaldehyde
o-Phthaldialdehyde
Phtalaldéhyde [French] [ACD/IUPAC Name]
Phthalaldehyd [German] [ACD/IUPAC Name]
Phthalaldehyde [ACD/IUPAC Name]
Phthaldialdehyde
VHR BVH [WLN]
[643-79-8]
o-phthalaldehyde
o-phthaldialdehyde
o-phthalicdicarboxaldehyde
1, 2-Phthalic dicarboxaldehyde
1,2-Diformylbenzene
4P8QP9768A
68234-47-9 [RN]
BR-44048
CHEBI 70851
D03470
Disopa
Disopa (TN)
MFCD00003335 [MDL number]
NCGC00166206-01
OPA
OPTA
P-6600
Phtalaldehydes [French]
Phthalic dicarboxaldehyde
Phthalyldicarboxaldehyde
Phtharal
Phtharal (JAN)
SBB008450
SS-7380
STR01056
TH6950000 [RTECS]
UNII-4P8QP9768A
オルトフタルアルデヒド [Japanese]

Definition: A dialdehyde in which two formyl groups are attached to adjacent carbon centres on a benzene ring.
phthalaldehyde is a benzaldehydes
phthalaldehyde is a dialdehyde

IUPAC Name
benzene-1,2-dicarbaldehyde
Synonyms    Sources
1,2-Benzenedicarboxaldehyde
1,2-Diformylbenzene
o-phthalaldehyde
o-Phthaldehyde
o-Phthaldialdehyde
o-Phthaldialdehyde
o-Phthalicdicarboxaldehyde
OPA   ChEBI
OPTA   ChEBI
Phthalaldialdehyde
Phthaldialdehyde
Phthalic aldehyde
Phthalic dialdehyde
Phthalic dicarboxaldehyde
Phthalyldicarboxaldehyde

OPA, amine detection reagent
Sensitive fluorescent detection reagent for amines (i.e. aa, proteins and peptides) Works also by absorbance; Can also be used for thiols detection.

Product Description
Part number: 02727A 1g
Chemical Name: o-Phtalaldehyde (OPA)
CAS 643-79-8, M.W.=134.12
 excitation = 340nm,  emission = 455nm
Storage : +4°C for long term (possible at room Temperature),protected from light and moisture (H)
OPA reagent provides a very high sensitivity detection reagent of amines, notably contained in proteins, peptides, and aminoacids.
It can also be used to quantitate thiols.
ATAMAN KIMYA offers a highly purified OPA for best results in HPLC, capillary electrophoresis, and spectrophotometric assays of protein/peptide and amino-acids

Scientific & technical Information
OPA is well soluble, and stable in water solution at pH<11.5. It is however sensitive to UV illumination and air oxidation.

In adequate conditions, OPA reacts in presence of thiols specifically with primary amines above their isoelectric point Pi.
The reaction during 1 minute (less for glycine).

The reaction starts within 15 seconds and can be monitored by absorbance, and by fluorescence.
The formed derivates are however not stable.

Absorbance at 340nm increase within 15seconds up to 1-3 minutes, then decreases more or less slowly. I.e.
AcetylCysteine maximum absorbance is maintained between 1’ and 1’30. One mole of NH2 gives on OD340nm of approximately 10 units.
Acetone and Dioxane don’t affect the assay.

A more sensitive detection is achieved by fluorescence, with excitation at 330-390nm (max.340nm), and measurement at 436-475nm (max 455nm).
There are noticeable variations of the fluorescent signal between amino-acids, and fluorescence might increase with pH values (not for histidine).
Thus it is recommended for accurate and sensitive results to use a purified standard homologous of the molecule of interest, to eventually optimize reaction duration and pH (between 9 and 11.5).

OPA
OPTA
Phthaldialdehyde
Phthalaldialdehyde
Phthalic dicarboxaldehyde
o-Phthalicdicarboxaldehyde
1,2-Diformylbenzene
o-Phthaldehyde
o-Phthaldialdehyde
Phthalyldicarboxaldehyde
1,2-Benzenedicarboxaldehyde
Phthalic dialdehyde
o-phthalaldehyde
Phthalic aldehyde
Turkish
No label defined
No description defined
Dutch
No label defined
chemische verbinding
German
Benzol-1,2-dicarbaldehyd
chemische Verbindung

O-phthalaldehyde (OPA) is a high-level disinfectant commonly used, for example, for sterilization of heat-sensitive medical instruments; it demonstrates effective microbicidal activity against a wide range of microorganisms (including mycobacteria, gramnegative bacteria, and spores).

A reagent that forms fluorescent conjugation products with primary amines.
It is used for the detection of many biogenic amines, peptides, and proteins in nanogram quantities in body fluids.

SYNONYMS
1. Aldehyde, Ortho-phthalic

2. O Phthalaldehyde

3. O Phthaldialdehyde

4. O-phthaldialdehyde

5. Ortho Phthalaldehyde

6. Ortho Phthalic Aldehyde

7. Ortho-phthalaldehyde

8. Ortho-phthalic Aldehyde

9. Orthophthaldialdehyde

SYNONYMS
1. 1,2-benzenedicarboxaldehyde

2. O-phthaldialdehyde

3. 643-79-8

4. Phthalaldehyde

5. Phthaldialdehyde

6. Phthalic Aldehyde

7. Benzene-1,2-dicarboxaldehyde

8. Phthalic Dialdehyde

9. Ortho-phthalaldehyde

10. O-phthaldehyde

11. Phthalyldicarboxaldehyde

12. Phthalic Dicarboxaldehyde

13. Benzene-1,2-dicarbaldehyde

14. 1,2-phthalic Dicarboxaldehyde

15. Phthalaldialdehyde

16. O-phthalic Dicarboxaldehyde

17. Opta

18. 1,2-diformylbenzene

19. Chebi:70851

20. Phthaldialdehyde Reagent

21. Phtalaldehydes [french]

22. O-phthalicdicarboxaldehyde

23. Opa

24. Unii-4p8qp9768a

25. Einecs 211-402-2

26. Nsc 13394

27. Brn 0878317

28. Ncgc00166206-01

29. Dsstox_cid_12514

30. Dsstox_rid_78962

31. Dsstox_gsid_32514

32. 30025-33-3

33. Cas-643-79-8

34. Ortho Phthalaldehyde

35. Orthophthaldialdehyde

36. Ortho-phthalic Aldehyde

37. Phthalaldehyd

38. Phtalaldehydes

39. Phtharal (jan)

40. Disopa (tn)

41. 2-phthaldehyde

42. Pubchem17402

43. 2-phthalaldehyde

44. Ac1l1izz

45. 2-phthaldialdehyde

46. Ortho-phthaladehyde

47. Epitope Id:176774

48. Ac1q6q8s

49. Agn-pc-0jk70r

50. O-phthalic Dialdehyde

51. P1378_sigma

52. Chembl160145

53. P0532_sial

54. P0657_sial

55. P7914_sial

56. Benzene-1,2-dialdehyde

57. 00681_fluka

58. 79760_fluka

59. 79760_sigma

60. Ctk1c4396

61. Timtec-bb Sbb008450

62. 1,2-benzenedicarbaldehyde

63. Molport-001-759-975

64. 4p8qp9768a

65. Bb_sc-4536

66. Nsc13394

67. Tox21_112347

68. Tox21_300404

69. Anw-49313

70. Ar-1l0930

71. Bbl027435

72. Nsc-13394

73. Sbb008450

74. Stk802214

75. Zinc01729594

76. Akos000119186

77. Tox21_112347_1

78. As03002

79. Bd21994

80. Mcule-5731001647

81. Rp20107

82. Rtr-033245

83. Ncgc00166206-02

84. Ncgc00166206-04

85. Ncgc00254339-01

86. Ac-10388

87. Ak-44048

88. Br-44048

89. Fluoraldehyde(tm) O-phthalaldehyde

90. Ls-109065

91. Tl8004558

92. Tr-033245

93. Am20050101

94. Ft-0085003

95. Ft-0632732

96. P0280

97. St51037395

98. D03470

99. P-6600

100. Z-3335

101. 4-07-00-02138 (beilstein Handbook Reference)

102. I01-0596

103. 3b3-001922

104. Inchi=1/c8h6o2/c9-5-7-3-1-2-4-8(7)6-10/h1-6

Fluoraldehyde crystals are o-phthalaldehyde (OPA), a highly sensitive fluorescent derivatization reagent for peptide or amino acid detection and quantitation in HPLC.

For pre- or post-column amino acid derivatization for fluorescent detection and quantitation
Reacts with all primary amine-containing analytes to yield fluorescent isoindole derivatives
Provides an accurate measure of both composition and absolute protein-peptide content
Ideal for work with recombinant proteins and synthetic peptides
Can be used for fluorescent protein or peptide assay
Can be prepared as a stable aqueous solution in borate

Fluoraldehyde crystals are a purified, fluorogenic-grade preparation of o-phthalaldehyde (OPA).
Fluoraldehyde reagent solution contains OPA which is supplied ready to use and enables fast quantitation of proteins or peptides in solu

Comparison of the mycobactericidal activity of ortho- phthalaldehyde, glutaraldehyde and other dialdehydes by a quantitative suspension test
S Fraud 1, J Y Maillard, A D Russell
Affiliations expand
• PMID: 11439009

• DOI: 10.1053/jhin.2001.1009
Abstract
The mycobactericidal activity of various dialdehydes has been assessed by a quantitative suspension test in both ‘clean’ and ‘dirty’ conditions.
Test organisms consisted of glutaraldehyde (GTA)-sensitive strains of Mycobacterium chelonae NCTC 946, M. abscessus NCTC 10882, two GTA-resistant M. chelonae strains and M. terrae NCTC 10856 (a proposed M. tuberculosis surrogate).
The aldehydes tested were a new high-level disinfectant, ortho-phthalaldehyde (OPA) at 0.5% (v/v) unadjusted pH 6.5 and pH 8, GTA at 0.5% (v/v) pH 8, glyoxal at 0.5% (v/v) pH 8 and 10% (v/v) unadjusted pH 2.8, malonaldehyde sodium salt (NaMDA) at 0.5% (w/v) pH 8 and 10% (w/v) unadjusted pH 7.5 and succinaldehyde at 0.5% (v/v) pH 8.
Results showed that 0.5% acidic and alkaline OPA were rapidly mycobactericidal, under both ‘clean’ and ‘dirty’ conditions, and more importantly were active against GTA-resistant strains.
The washer disinfector isolates of M. chelonae were, as expected, extremely resistant to 0.5% GTA which was slowly mycobactericidal against the other strains.
Glyoxal, NaMDA and succinaldehyde were ineffective against all the strains investigated.
However, a high concentration of glyoxal exhibited a slow mycobactericidal activity except with M. terrae NCTC 10856, but this was not observed with NaMDA.

This evaluation, using a quantitative suspension test based on a European standard, supported the claim that OPA is an effective choice as a high-level disinfectant for medical devices.

J Antimicrob Chemother
. 2003 Mar;51(3):575-84. doi: 10.1093/jac/dkg099.
Effects of ortho-phthalaldehyde, glutaraldehyde and chlorhexidine diacetate on Mycobacterium chelonae and Mycobacterium abscessus strains with modified permeability
S Fraud 1, A C Hann, J-Y Maillard, A D Russell
Affiliations expand
PMID: 12615857 DOI: 10.1093/jac/dkg099
Abstract
The mechanisms of the mycobactericidal action of ortho-phthalaldehyde (OPA), glutaraldehyde (GTA) and chlorhexidine diacetate (CHA) were investigated using mycobacterial spheroplasts of two reference strains, Mycobacterium chelonae NCTC 946, Mycobacterium abscessus NCTC 10882 and two GTA-resistant strains, M. chelonae Epping and M. chelonae Harefield.
Transmission electron microscopy of the spheroplasts revealed an altered cell wall structure compared with the parent cells.
Structural alterations resulting from the spheroplasting process were in part correlated to a loss of lipid content.
Low concentrations of CHA induced protein coagulation in M. chelonae NCTC 946 spheroplasts, which also exhibited the highest loss of free non-polar lipids.
Higher concentrations of CHA were required to produce similar results to the other spheroplasts investigated in which there was a less substantial decrease in lipid content. OPA (0.5% w/v) readily penetrated the residual cell wall and cytoplasmic membrane, producing significant protein coagulation in M. chelonae NCTC 946.
GTA (0.5% v/v) induced a similar effect but to a lesser extent.
Pre-treatment of the spheroplasts with OPA and GTA and their subsequent suspension in water demonstrated that GTA was a more potent cross-linking agent.
This protective effect of GTA results from extensive cross-linking of amino and/or sulphydryl side-chain groups of proteins.
The rapid mycobactericidal effect of OPA probably arises from its more efficient penetration across biological membranes.
Mycobacterial spheroplasts represented a useful cellular model with an altered cell wall permeability.
This study also showed the importance of the mycobacterial cell wall in conferring intrinsic resistance to CHA.

Use of a new alginate film test to study the bactericidal efficacy of the high-level disinfectant ortho-phthalaldehyde
J C N Shackelford 1, G W Hanlon, J-Y Maillard
Affiliations expand
PMID: 16332730 DOI: 10.1093/jac/dki432
Abstract
Objectives: To evaluate the merit of a new alginate efficacy film test to determine the bactericidal activity of the high-level disinfectant ortho-phthalaldehyde (OPA).

Methods: The efficacy of OPA was investigated using a new sodium alginate surface film test against Mycobacterium chelonae NCIMB 1474 and Epping, and Pseudomonas aeruginosa NCIMB 10421 under different test conditions.

Results: OPA was highly bactericidal against P. aeruginosa but its mycobactericidal efficacy was seriously reduced and produced >or=5 log reductions only at a concentration of 0.5% (w/v) within 30-60 min without organic load.

Conclusions: The sodium alginate film efficacy was reproducible between repeats.
Inactivation results depended upon the concentration of OPA, contact time, the presence of an organic load and the bacterial genera.

Comparison between Glutaraldehyde and Ortho-Phthalaldehyde Air Levels during Endoscopic Procedures
Author links open overlay panelC.Marena∗L.LodolaR.LodiL.Zambianchi

Abstract
BACKGROUND: Glutaraldehyde (GTA) has been used as a disinfecting agent for over 30 years, but irritative effects on the skin and respiratory tract have been described.
The risk to healthcare personnel and emerging of GTA-resistant microorganisms have highlighted the need to develop new agents. One possible alternative to GTA is ortho-phthalaldehyde (OPA), which has a similar capacity to kill bacteria and a very good toxicological profile.

OBJECTIVE: To compare air levels of GTA and OPA during high-level disinfection of endoscopes.

METHODS: The comparative study was carried out in ten endoscopy units of the San Matteo Hospital, where GTA and OPA were routinely used for the low-temperature disinfection of endoscopes.
GTA and OPA were used under the same operating procedures and for the same exposure time (4 hours).

The monitoring of air levels was performed with both HPLC-UV (High Performance Liquid Chromatography with UV detection) and Infrared Spectroscopy (IR).

RESULTS: The HPLC method gave a much lower aldheyde value when using OPA (8.4 mg/m3) compared to that obtained when GTA was used to disinfect endoscopes (21279.3 mg/m3).
These results were confirmed with IR detection method (the mean values being below 10 mg/m3).
In addition, we studied the resistance of various glove types to OPA.
Tests showed that OPA-permeated vinyl gloves more rapidly (26628 ng/cm2 per hour) than nitrile gloves (13.9 ng/cm2 per hour).

CONCLUSION: This study showed a very low air concentration of OPA compared to GTA.
These findings confirm the excellent safety profile of OPA used as a high-level disinfectant in the hospital setting.

Effects of ortho-phthalaldehyde, glutaraldehyde and chlorhexidine diacetate on Mycobacterium chelonae and Mycobacterium abscessus strains with modified permeability
S. Fraud, A. C. Hann, J.-Y. Maillard, A. D. Russell
Journal of Antimicrobial Chemotherapy, Volume 51, Issue 3, March 2003, Pages 575–584, https://doi.org/10.1093/jac/dkg099
Published: 01 March 2003

Abstract
The mechanisms of the mycobactericidal action of ortho-phthalaldehyde (OPA), glutaraldehyde (GTA) and chlorhexidine diacetate (CHA) were investigated using mycobacterial spheroplasts of two reference strains, Mycobacterium chelonae NCTC 946, Mycobacterium abscessus NCTC 10882 and two GTA-resistant strains, M. chelonae Epping and M. chelonae Harefield.
Transmission electron microscopy of the spheroplasts revealed an altered cell wall structure compared with the parent cells.
Structural alterations resulting from the spheroplasting process were in part correlated to a loss of lipid content.
Low concentrations of CHA induced protein coagulation in M. chelonae NCTC 946 spheroplasts, which also exhibited the highest loss of free non-polar lipids.
Higher concentrations of CHA were required to produce similar results to the other spheroplasts investigated in which there was a less substantial decrease in lipid content.
OPA (0.5% w/v) readily penetrated the residual cell wall and cytoplasmic membrane, producing significant protein coagulation in M. chelonae NCTC 946. GTA (0.5% v/v) induced a similar effect but to a lesser extent.
Pre-treatment of the spheroplasts with OPA and GTA and their subsequent suspension in water demonstrated that GTA was a more potent cross-linking agent.
This protective effect of GTA results from extensive cross-linking of amino and/or sulphydryl side-chain groups of proteins.
The rapid mycobactericidal effect of OPA probably arises from its more efficient penetration across biological membranes.
Mycobacterial spheroplasts represented a useful cellular model with an altered cell wall permeability.
This study also showed the importance of the mycobacterial cell wall in conferring intrinsic resistance to CHA.

Introduction
Non-tuberculous mycobacteria (NTM) are defined as those mycobacteria that are not part of the Mycobacterium tuberculosis complex.
Many NTM are free-living saprophytes that are widely distributed in a variety of environments such as soil, water, dust and aerosols.
The rapidly growing NTM such as Mycobacterium chelonae, Mycobacterium abscessus and Mycobacterium fortuitum also comprise a major cause of opportunistic hospital-acquired infections in immunocompromised patients.
In medical care units, the spread of these atypical mycobacteria can be reduced by adequate disinfection of equipment, the local environment and the staff.

Mycobacteria as a group are highly impermeable to hydrophilic molecules, including nutrient molecules such as glucose and glycerol, and antibiotics such as β-lactams.
It is well established that the complex lipid-rich mycobacterial cell wall, which constitutes an efficient impermeability barrier, plays a major role in the intrinsic resistance of mycobacteria to antibiotics, antiseptics and disinfectants.

In this study, we have focused our attention on the mechanisms of action of some biocides that are widely used in hospital environments and particularly on some aldehydes used for high-level disinfection in endoscopy units.
The bisbiguanide chlorhexidine, used as the diacetate or gluconate, is a clinically important antiseptic (hand-washing and oral products), disinfectant and preservative.
Mycobacteria are generally highly resistant to chlorhexidine diacetate (CHA), but the MICs for some mycobacterial strains are of the order of those for CHA-sensitive Gram-positive cocci.
The mechanism by which CHA is mycobacteriostatic rather than mycobactericidal remains unknown, although the cell wall permeability barrier seems to play an important role.
Glutaraldehyde (GTA) remains a popular high-level disinfectant for flexible endoscope disinfection despite its slow mycobactericidal activity and the increasing emergence of 2% v/v GTA-resistant M. chelonae strains isolated from endoscope washer disinfectors.
More recently, ortho-phthalaldehyde (OPA), an aromatic dialdehyde, has been proposed as a possible alternative to GTA for high-level disinfection of endoscopes.
A previous study demonstrated the rapid efficacy of 0.5% w/v OPA against a range of NTM and more importantly against GTA-resistant mycobacterial strains.

Bacterial spheroplasts exhibit a residual altered cell wall structure and composition, and we have used such models to obtain information about:
(i) the nature and role of the mycobacterial cell wall in conferring resistance to CHA;
(ii) the role of the permeability barrier represented by the mycobacterial cell wall towards OPA and GTA; and
(iii) the possible protective effect, associated with cross-linking properties, of OPA and GTA in preventing spheroplast lysis in water

ABSTRACT
This study investigated the use of a rapid bacterial toxicity test for detecting disinfectant residues released by disinfected materials.
The test substances included an environmental disinfectant used in hospitals in high-risk areas, such as critical care units or emergency services, and three disinfectants used on clinical devices when a high level of disinfection is required.
The test materials were polyurethane, polypropylene, glass, latex and cotton from different instruments and utensils used in hospitals.
Of the four test disinfectants, o-phthalaldehyde (OPA) and 2-bromo-2-nitro-1,3-propanediol (BNP) showed the greatest inhibitory activity (as much as 300-fold greater than hydrogen peroxide in the case of OPA) according to the toxicity text.
However, with the exception of hydrogen peroxide on latex, it was the most porous test materials, namely latex and cotton, that accumulated the least residue.
BNP was the disinfectant that left the least residue on the five test materials, while the greatest residual concentration was left by hydrogen peroxide on latex (as much as 5 µg/cm 2).
The biotest used in this study permitted the detection of disinfectant residues released by different types of previously disinfected clinical materials, and can be adapted to simulate elution conditions similar to those existing in routine hospital practice.

BACKGROUND: Glutaraldehyde (GTA) has been used as a disinfecting agent for over 30 years, but irritative effects on the skin and respiratory tract have been described.
The risk to healthcare personnel and emerging of GTA-resistant microorganisms have highlighted the need to develop new agents.
One possible alternative to GTA is ortho-phthalaldehyde (OPA), which has a similar capacity to kill bacteria and a very good toxicological profile.
OBJECTIVE: To compare air levels of GTA and OPA during high-level disinfection of endoscopes.
METHODS: The comparative study was carried out in ten endoscopy units of the San Matteo Hospital, where GTA and OPA were routinely used for the low-temperature disinfection of endoscopes.
GTA and OPA were used under the same operating procedures and for the same exposure time (4 hours).
The monitoring of air levels was performed with both HPLC-UV (High Performance Liquid Chromatography with UV detection) and Infrared Spectroscopy (IR).

In addition, we studied the resistance of various glove types to OPA.
Tests showed that OPA-permeated vinyl gloves more rapidly (26628 ng/cm2 per hour) than nitrile gloves (13.9 ng/cm2 per hour).

Numerous case reports have been published indicating workers and patients experiencing respiratory problems, anaphylaxis, skin reactivity, and systemic antibody production. Our laboratory previously demonstrated that OPA is a dermal sensitizer in mice. The goal of the present study was to determine if OPA is a respiratory sensitizer following inhalation exposure. Mice were exposed to OPA vapor and airway and lymph nodes were examined for cytokine gene expression and alterations in lymphocyte populations. Inhalation of OPA for 3 days resulted in a concentration-dependent increase in lymphocyte proliferation, mainly B lymphocytes, in the draining lymph nodes. A secondary challenge of mice with OPA resulted in a dramatic increase in the population of B lymphocytes expressing IgE. Expression of Th2 (IL-4, IL-5, and IL-13) and anti/proinflammatory (IL-10, TNFα, and IL-1β) cytokine genes was upregulated in the lymph nodes and the nasal mucosa. Mice exposed to the higher concentrations of OPA-produced OPA-specific IgG1 antibodies indicating systemic sensitization. These findings provide evidence that OPA has the potential to cause respiratory sensitization in mice.

1. Introduction
Ortho-Phthalaldehyde (OPA) is an aromatic dialdehyde, used as a high-level antimicrobial disinfectant for medical equipment which is sensitive to normal heat or steam sterilization processes, including endoscope, cystoscopes, and certain dental instruments.
For 40 years, glutaraldehyde, another dialdehyde, has been the primary choice for disinfecting heat-sensitive medical devices; however, it has been reported to be a chemical sensitizer.
Glutaraldehyde is known to have high affinity for biological amines, and its use as a tissue fixative capitalizes on this property.
As such, glutaraldehyde and dialdehydes as a chemical class can bind to native proteins, thus, altering their presentation to the immune system.
Haptenization of native proteins can lead to an aberrant immune response and the development of allergy.
Several human studies have demonstrated the presence of IgE antibodies specific for glutaraldehyde adducts in the serum of exposed workers with respiratory disease.
Importantly, workplace exposure to glutaraldehyde is known to induce occupational asthma and allergic contact dermatitis suggesting the need for safer alternatives.
OPA has shown superior antimycobactericidal activity as compared to glutaraldehyde, allowing for its use at lower concentrations.
In addition, low volatility and no need for activation have increased the use of OPA as a more practical alternative to glutaraldehyde.

It is estimated that 3253 workers were potentially exposed to OPA compared to 376,330 for glutaraldehyde from 1981–1983.
If OPA was fully adopted as an alternative for glutaraldehyde, it is a reasonable assumption that more than 300,000 US workers could now be exposed. The estimated use of OPA in 2002 was between 10,000 and 500,000 pounds.
OPA is commonly considered as a “safe” alternative to glutaraldehyde despite a paucity of information regarding the toxicity of this chemical and the potential health effects associated with exposure.
Very few toxicology studies are available in the published literature to establish the safety of OPA.
The few toxicity studies that have been performed suggest that OPA may be a chemical irritant and sensitizer and may act as an adjuvant for other allergens.

Currently there are no regulations regarding proper use and safe exposure levels of OPA in spite of the potential of exposure for a large number of healthcare workers and their patients.
Concentrations of OPA ranging from 1.0 to 13.5 ppb have been detected in air samples collected from an endoscope cleaning unit of a hospital that used OPA as its primary disinfectant.

Several case reports have been presented in the literature questioning the safe substitution of OPA as a high-level sterilant in the healthcare industry.
Fujita et al. investigated a case involving a female nurse who exhibited slight dyspnea and dry cough that began a few months after switching to OPA for high-level sterilization in the endoscopy unit.
The patient was subsequently diagnosed with bronchial asthma and experienced episodic attacks when working in the endoscopy unit.
Another report identified four patients who experienced nine episodes of anaphylaxis with associated respiratory symptoms after a urology practice switched from using glutaraldehyde to OPA for cystoscope disinfection.
In a separate report, anaphylactic reactions with respiratory involvement occurred in two bladder cancer patients following repeated cystoscopic examination of their tumors and a woman receiving repeated checkups by laryngoscopy.
Two potential cases of occupational asthma in healthcare workers disinfecting endoscopes and similar devices with OPA have also been reported.
These case reports demonstrate that occupational and medical exposure to OPA can induce systemic anaphylaxis as well as pose a risk of respiratory sensitization.

Toxicity data derived from animal studies will be important for regulating and setting occupational exposure limits for OPA.
The laboratory recently demonstrated that mice dermally exposed to OPA tested positive in the local lymph node assay (LLNA) with associated increases in total and OPA-specific IgE levels, suggesting an IgE-mediated allergic mechanism.
The EC3 value for OPA was 0.051%, ten-fold lower than the working concentration for disinfection, establishing this chemical as a strong dermal sensitizer.
The goal of the present studies was to determine the respiratory sensitization potential of inhalation exposure to OPA vapor.

OPA : HIGH-LEVEL DISINFECTANTS ALTERNATIVE TO GLUTARALDEHYDE FOR PROCESSING FLEXIBLE ENDOSCOPES
ABSTRACT: Flexible endoscopes are fundamental in various medical specialities; in general they are heat-sensitive, semi-critical, and subject to high level disinfection.
Glutaraldehyde is largely used for this purpose, due to its high compatibility and low-cost.
However, its tolerance of mycobacteria and occupational toxicity lead to pressure being applied for the adoption of alternative germicides.
A systematic review was undertaken aiming to seek evidence regarding the effectiveness, toxicity and potential harm caused to the endoscopes by those germicides which are alternative to glutaraldehyde and which are available on the market in Brazil.
A total of 822 publications was identified in 13 electronic databases, between 2008 and 2013. Of these, 23 studies were selected, considering the best quality of evidence available.
The publications point to the superiority of peracetic acid and of orthophthaldehyde regarding efficacy in high level disinfection.
Only orthophthaldehyde presented an adverse event clearly related to its use.
There is insufficient evidence to assert that any of these germicides has greater potential for harm to the equipment.
DESCRIPTORS: Disinfection; Endoscopes; Glutaraldehyde;

Orthophthaldehyde (OPA) is a soluble and stable aldehyde with a blue coloring, pH of 7.5, sensitive to ultraviolet light and to oxidation by the air; its mechanism of action is similar to that of GLU, although with low sporicidal action, which occurs through blocking germination.
This aldehyde can be used manually or automatically, in concentrations of 0.55%; in spite of being less volatile than GLU, it also needs to be handled in an appropriately-ventilated area using personal protective equipment

Evaluation of the respiratory tract toxicity of ortho-phthalaldehyde, a proposed alternative for the chemical disinfectant glutaraldehyde

ortho-Phthalaldehyde (OPA) is a high-level chemical disinfectant that is commonly used for chemical sterilization of dental and medical instruments as an alternative to glutaraldehyde, a known skin and respiratory sensitizer.
Concern for safe levels of human exposure remains due to a lack of toxicity data as well as human case reports of skin and respiratory sensitization following OPA exposure.
The present study evaluated the inhalational toxicity of OPA in Harlan Sprague–Dawley rats and B6C3F1/N mice.
Groups of 10 male and female rats and mice were exposed to OPA by whole-body inhalation for 3 months at concentrations of 0 (control), 0.44, 0.88, 1.75, 3.5, or 7.0 ppm.

Rats and mice developed a spectrum of lesions at sites of contact throughout the respiratory tract (nose, larynx, trachea, lung), as well as in the skin and eye, consistent with a severe irritant response. In general, histologic lesions (necrosis, inflammation, regeneration, hyperplasia and metaplasia) occurred at deeper sites within the respiratory tract with increasing exposure concentration.
As a first site of contact, the nose exhibited the greatest response to OPA exposure and resulted in an increased incidence, severity and variety of lesions compared to a previous study of glutaraldehyde exposure at similar exposure concentrations. This increased response in the nasal cavity, combined with extensive lesions throughout the respiratory tract, provides concern for use of OPA as a replacement for glutaraldehyde as a high-level disinfectant.

o-Phthalaldehyde
643-79-8
PHTHALALDEHYDE
o-Phthaldialdehyde
1,2-Benzenedicarboxaldehyde
Benzene-1,2-dicarboxaldehyde
Phthaldialdehyde
Phthalic aldehyde
Phthalic dialdehyde
ortho-Phthalaldehyde
Phthalyldicarboxaldehyde
Phthalic dicarboxaldehyde
o-Phthaldehyde
benzene-1,2-dicarbaldehyde
Phthalaldialdehyde
o-Phthalicdicarboxaldehyde
1,2-Diformylbenzene
2-PHTHALALDEHYDE
1,2-Phthalic dicarboxaldehyde
ortho Phthalaldehyde
o-Phthalic dicarboxaldehyde
1,2-BENZENEDICARBALDEHYDE
OPA
OPTA
Phtalaldehydes [French]
MFCD00003335
NSC 13394
UNII-4P8QP9768A
CHEBI:70851
2-PHTHALDIALDEHYDE
EINECS 211-402-2
BRN 0878317
4P8QP9768A
NCGC00166206-01
DSSTox_CID_12514
DSSTox_RID_78962
DSSTox_GSID_32514
Phtalaldehydes
1,2-Phthalic dicarboxaldehyde, 98+%
CAS-643-79-8
Orthophthaldialdehyde
ortho-Phthalic Aldehyde
phthalaldehyd
o-Phthalaldehyd
o-phthal aldehyde
orthophthalaldehyde
Phtharal (JAN)
Disopa (TN)
2-PHTHALDEHYDE
Phthaldialdehyde Reagent
PubChem17402
ORTHO-PHTHALADEHYDE
Epitope ID:176774
O-PHTHALIC DIALDEHYDE
2-Phthaldehyde, High purity
SCHEMBL33393
4-07-00-02138 (Beilstein Handbook Reference)
1,2-Phthalic dicarboxyaldehyde
CHEMBL160145
Ortho-Phthalic Aldehyde (OPA)
BENZENE-1,2-DIALDEHYDE
DTXSID6032514
CTK1C4396
HSDB 8456
TIMTEC-BB SBB008450
BCP29465
EBD34601
NSC13394
STR01056
ZINC1729594
Tox21_112347
Tox21_300404
1,2-Benzenedialdehyde;Phthalaldehyde
ANW-49313
BBL027435
NSC-13394
SBB008450
STK802214
AKOS000119186
Tox21_112347_1
AS03002
CS-W013385
LS1185
MCULE-5731001647
KS-0000022J
NCGC00166206-02
NCGC00166206-04
NCGC00254339-01
AC-10388
AK-44048
BR-44048
FLUORALDEHYDE(TM) O-PHTHALALDEHYDE
SC-17674
Benzene-1,2-dicarboxaldehyde 643-79-8
Phthaldialdehyde Reagent, Solution Complete
LS-109065
AM20050101
FT-0632732
P0280
Phthaldialdehyde Reagent, Solution Incomplete
ST51037395
43P798
D03470
P-6600
Z-3335
SR-01000944839
Q5933776
SR-01000944839-1
Phthaldialdehyde, for fluorescence, >=99.0% (HPLC)
6-Oxomethylene-5-[(E)-hydroxymethylene]cyclohexa-1,3-diene
6-Oxomethylene-5-[(Z)-hydroxymethylene]cyclohexa-1,3-diene
Phthaldialdehyde, >=97% (HPLC), powder (may contain lumps)
Phthaldialdehyde, suitable for HPLC fluorimetric detection of amino acids, >=99% (HPLC), powder

Evaluation of the Antimicrobial Activity and Materials Compatibility of Orthophthalaldehyde as a High-level Disinfectant
T AKAMATSU1, M MINEMOTO1 AND M UYEDA 2
1Department of Pharmacy, Kyushu Kosei-Nenkin Hospital, Kitakyushu, Japan;
2Faculty of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan

We tested the antimicrobial activity of orthophthalaldehyde (OPA) against 21 strains (16 species) of pathogenic microorganisms that cause hospitalassociated infections.
Changes in hepatitis B surface antigen (HBs-Ag) resulting from the addition of OPA to HBs-Ag-positive serum were measured using a radioimmunoassay.
We also examined the effect of immersing medical instruments in OPA (0.55%) for 168 h at room temperature.
OPA (0.5%, 0.37% and 0.25%) killed 11 strains of vegetative bacteria within 15 s, and it killed the test microorganisms faster than 3.0% glutaraldehyde (GTA).
Incubation with OPA or GTA caused levels of HBs-Ag to fall below a cut-off value within 30 s.
OPA did not adversely affect instruments made from various materials.
OPA demonstrated more effective antimicrobial activity than GTA against a range of micro-organisms.
We conclude that OPA should replace GTA as the first-choice high-level disinfectant for endoscopes, considering its antimicrobial efficacy and low inhalation toxicity

ANTIMICROBIAL ACTIVITY
The antimicrobial activities of aqueous solutions of OPA and GTA against the test micro-organisms are shown in Tables 1 – 3. Each of the three concentrations of OPA killed all 11 vegetative bacteria within 0.25 min.
The five strains of mycobacteria were more resistant, requiring 1 min, 1 min and 1 – 3 min to be killed by 0.5%, 0.37% and 0.25% OPA, respectively.

Like the vegetative bacteria, the fungus C. albicans was killed within 0.25 min by OPA at all concentrations tested.
M. racemosus, R. nigricans, A. niger and A. terreus, sporeforming fungi, were killed within 1 min by OPA at all concentrations tested.
Orthophthalaldehyde showed more potent activity than GTA against all 21 strains used in this study.
Furthermore, OPA retained similar antimicrobial activity with or without the addition of 10% human serum.

We compared OPA and GTA with respect to the two attributes that are essential for a high-level disinfectant:
fast-acting antimicrobial effects against a broad range of pathogenic micro-organisms; and compatibility with materials used for medical instruments.

The two agents were tested for their effects against various vegetative bacteria, mycobacteria and fungi that cause important hospital-associated infections.
OPA concentrations of 0.5%, 0.37% and 0.25% were selected, to take into consideration the decrease of OPA concentration that might be expected to occur over time in automatic cleaning machines for endoscopes.
The results showed that even the lowest dose of OPA (0.25%) was faster acting than GTA (3.0%) in terms of its antimicrobial affects against all of the 21 strains tested.
The germicidal effects of OPA were not diminished significantly in the presence of 10% human serum.
Activity against hepatitis B virus was tested using serum from an HBs-Ag-positive patient.
Inactivation of HBs-Ag is not the same as loss of hepatitis B virus infectivity, but there have been numerous studies conducted both in animals and patients with liver transplantations suggesting that reactivation of the virus does not occur in the absence of HBs-Ag.
Thus, our results indicated that OPA treatment is likely to result in a loss of infectivity of hepatitis B virus.
The World Health Organization recommends hypochlorous acid and GTA as an effective disinfectant against hepatitis B virus; our results show that OPA is also an effective disinfectant against hepatitis B virus.

Orthophthalaldehyde, like GTA, did not corrode any of the materials used to manufacture the medical instruments we evaluated, and the test was designed to recreate the prolonged and repeated use seen with fiberscope disinfection.
The chemical stability of OPA solution (as measured by the change in OPA concentration over time in automatic cleaning machines, particularly those used for cleaning endoscopes) was not examined in this study.
The antimicrobial efficacy of OPA at a low concentration (0.25%) demonstrated in this study is believed to support the results obtained by Alfa and Sitter however, which showed that OPA maintained its antimicrobial activities during repeated use for 14 days.
Orthophthalaldehyde does not have an irritating odour, which is the biggest shortcoming of GTA, and does need to be reactivated for use.
On these grounds alone, OPA may be a more satisfactory agent for medical staff responsible for cleaning and disinfecting endoscopes.
We conclude that as well as having attributes like low odour, OPA is an effective antimicrobial agent and should be the first-choice agent to replace GTA as a high-level disinfectant for endoscopes.

Ortho-phthalaldehyde (OPA) has been around since the early 1990s as a safer disinfectant active for treating instruments and devices, in comparison to glutaraldehyde.
OPA is found to be very compatible with most materials used to manufacturer medical instruments.

Contrary to common belief,

Ortho phthalaldehyde is one of the members of the aldehyde family that does not have the characteristic pungent odor associated with formaldehyde etc.

Orthophthalaldehyde is known to maintain its biocidal activity in a wide range of pH, while being compatible with various materials and equipment.

Ortho phthalaldehyde causes malfunction of the bacterial cell membrane by attaching to protein residues and receptors and which also increases the permeability to OPA allowing the chemical to enter the cell.

Once in the cell, OPA interacts with enzymes and RNA and thus causes failure of cellular functions, which leads to bacterial cell death.

Ortho phthalaldehyde at various use dilution is known to be a bactericide, virucide, fungicide, and tuberculocide and is widely used as a high level disinfectant for reprocessing semi-critical medical devices (e.g. items that will come in contact with mucous membranes or non-intact skin).

Sporicidal activity OPA is very limited and dependent on the pH and the contact time is considered to be too long to be useful for reprocessing activities.

At use dilution of 0.5% to 5%, OPA does not impose any flammability or reactivity hazards.
There has been reports of residual OPA exposure from endoscopes and trans-esophageal probes to patients, where it has caused exacerbation of asthma and bronchitis, and general sensitization.
At use dilution, OPA is found to be a sensitizer to eye, skin and respiratory organs, however, current scientific evidence has not found OPA to be mutagenic or carcinogenic.

Ortho phthalaldehyde is very toxic to aquatic organisms and forms toxic biodegradation by-products; bio-accumulation is not repo rted.
Here’s how we would score Ortho phthalaldehyde on the key decision making criteria:
• Speed of Disinfection – A to D

o High Level Disinfection within 5 – 12 minutes
o Sporicidal contact time prohibitive to use as a chemical sterilant
• Spectrum of Kill – A

o Achieves disinfection against all microorganisms; bacteria, viruses, fungi, mycobacteria and spores
• Cleaning Effectiveness – N/A

o No detergent properties
o High Level Disinfection and Chemical Sterilization requires instruments to cleaned prior to moving to the disinfection or sterilization process

• Safety Profile – C

o Minimal long term toxicity data
o OPA has been contraindicated for use on urological instruments due to anaphylaxis
• Environmental Profile – D

o Restrictions in disposal
• Cost Effectiveness – B to C

o The original patent for OPA has expired and is now available from a number of suppliers

Ortho-phthalaldehyde is a Reliable Chemical Sterilant

Ortho-phthalaldehyde (OPA) received clearance by FDA in October 1999.
OPA solution is a clear, pale-blue liquid (pH, 7.5), which typically contains 0.55% OPA.
OPA has demonstrated excellent microbiocidal activity in in vitro studies.
For example, it has shown superior mycobactericidal activity (5-log10 reduction in 5 minutes) compared with glutaraldehyde.
The mean time required to effect a 6-log10 reduction for M. bovis using 0.21% OPA was 6 minutes, compared with 32 minutes using 1.5% glutaraldehyde.
When tested against a wide range of microorganisms, including glutaraldehyde-resistant mycobacteria and Bacillus subtilis spores, OPA showed good activity against the mycobacteria tested, including the glutaraldehyde-resistant strains, but 0.5% OPA was not sporicidal within 270 minutes of exposure.
Increasing the pH from its unadjusted level (about 6.5) to pH 8 improved sporicidal activity.

OPA has several potential advantages compared with glutaraldehyde.
It requires no activation, is not a known irritant to the eyes and nasal passages, has excellent stability over a wide range of pH (pH 3-9), does not require exposure monitoring, and has a barely perceptible odor.

Ortho-phthalaldehyde (OPA) was tested against a range of organisms including glutaraldehyde-resistant mycobacteria, Bacillus subtilis spores and coat-defective spores.
Glutaraldehyde (GTA) and peracetic acid (PAA) were tested for comparative purposes.
Both suspension and carrier tests were performed using a range of concentrations and exposure times.
All three biocides were very effective (> or = 5 log reduction) against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa in suspension tests.
OPA and GTA were also very effective against Staph. aureus and Ps. aeruginosa in carrier tests.
OPA showed good activity against the mycobacteria tested including the two GTA-resistant strains, but 0.5% w/v OPA was found not to be sporicidal.
However, limited activity was found with higher concentrations and pH values.
Coat-defective spores were more susceptible to OPA, suggesting that the coat may be responsible for this resistance.
The findings of this study suggest that OPA is effective against GTA-resistant mycobacteria and that it is a viable alternative to GTA for high level disinfection.

If you’d like more details on OPA performance or interested in analyzing a sample, please contact us.

The Mycobactericidal Efficacy of Ortho-Phthalaldehyde and the Comparative Resistances of Mycobacterium bovis, Mycobacterium terrae, and Mycobacterium chelonae
Published online by Cambridge University Press: 02 January 2015

Abstract
Objectives:
To assess the mycobactericidal efficacy of an agent relatively new to disinfection, ortho-phthalaldehyde (OPA) and to compare the resistances of three Mycobacterium species.
Mycobacterium bovis (strain BCG) was compared with Mycobacterium chelonae and Mycobacterium terrae to investigate the feasibility of using either of the latter two species in tuberculocidal testing.
M chelonae (a rapid grower) and M terrae (an intermediate grower) both grow faster and are less virulent than M bovis (a slow grower).

Design:
The quantitative suspension protocol specified by the Environmental Protection Agency (EPA), the Tuberculocidal Activity Test Method (EPA test), was used throughout this study.
Standard suspensions of all three species were prepared in a similar manner.
Two suspensions of M bovis, created in different laboratories, were used.
These were tested against two concentrations of alkaline glutaraldehyde to provide reference data.
Two concentrations of OPA were evaluated against all mycobacterial test suspensions.
Four replicates of each organism-disinfectant combination were performed.

Results:
Results were assessed by analysis of variance. M terrae was significantly more resistant to 0.05% OPA than either M bovis or M chelonae.
At 0.21% OPA, M terrae was slightly more susceptible than one test suspension of M bovis, but not significantly different from the other.
M chelonae was significantly less resistant than the other species at both OPA concentrations.
At their respective minimum effective concentration, OPA achieved a 6-log10 reduction of M bovis in nearly one sixth the time required by glutaraldehyde (5.5 minutes vs 32 minutes).

Conclusions:
These data, along with other recent studies, lend support to the idea that M terrae may be a suitable test organism for use in the tuberculocidal efficacy testing of disinfectants.
They also confirm the relatively rapid tuberculocidal activity of OPA.

o-Phthalaldehyde is mainly used as a high-level disinfectant (a low-temperature chemical method) for heat-sensitive medical and dental equipment such as endoscopes and thermometers; in recent years, it has gained popularity as a safe and better alternative to glutaraldehyde.
There are some researches show, pH7.5 contains the sterilizing agent of o-phthalaldehyde 0.5%, and its sterilizing power, sterilization speed, stability and toxicity all are better than glutaraldehyde, can kill mycobacterium in the 5min, the bacterium number reduces by 5 logarithmic value, and o-phthalaldehyde is very stable, tasteless in pH3～9 scopes, non-stimulated to human nose, eye mucosa, and need not activate before using, various materials are had good consistency, have tangible microbiocidal activity.

Uses
o-Phthalaldehyde can be widely used for precolumn derivatization of amino acids in HPLC separation or Capillary electrophoresis. For flow cytometric measurements of protein thiol groups.

Uses
o-Phthalaldehyde can be used for precolumn derivatization of amino acids for HPLC separation and for flow cytometric measurements of protein thiol groups.

Uses
Precolumn derivatization reagent for primary amines and amino acids. The fluorescent derivative can be detected by reverse-phase HPLC.
The reaction requires OPA, primary amine and a sulfhydryl. In the presence of excess sulfhydryl, amines can be quantitated.
In the presence of excess amine, sulfhydryls can be quantitated.

Uses
Disinfectant.
Reagent in fluorometric determination of primary amines and thiols.

Preparation
o-Phthalaldehyde is a high-level chemical disinfectant that is commonly used for disinfection of dental and medical instruments as an alternative to glutaraldehyde, which is a known skin and respiratory sensitizer.
A variety of processes for manufacturing o-phthalaldehyde have been reported in the literature.
o-Phthalaldehyde is produced by heating pure benzaldehyde and chloroform with potassium hydroxide solution.
The resulting solution is further acidified with hydrochloric acid and cooled to yield a colorless powder of o-phthalaldehyde.
It is also produced by ozonization of naphthalene in alcohol followed by catalytic hydrogenation.
Catalytic oxidation of various chemicals is also used in manufacturing o-phthalaldehyde.
o-Phthalaldehyde can be manufactured by oxidation of phthalan by nitrogen monoxide in acetonitrile with N-hydroxyphthalimide as the catalyst to yield 80% to 90%.

Definition
ChEBI: A dialdehyde in which two formyl groups are attached to adjacent carbon centres on a benzene ring.

Synthesis Reference(s)
Journal of the American Chemical Society, 73, p. 1668, 1951 DOI: 10.1021/ja01148a076
Tetrahedron Letters, 27, p. 1793, 1986 DOI: 10.1016/S0040-4039(00)84377-4

Biotechnological Applications
O-phthalaldehyde (OPA) is used for precolumn derivatization of amino acids for HPLC separation and for flow cytometric measurements of protein thiol groups.
Used for fluorometric determination of histamine, histidine and other amino acids. Also used for cholesterol assay in the picomole range.

Phthaldialdehyde has been used:
in the preparation of O-phthaldialdehyde reagent for analysing gentamycin content.
in the preparation of reagent for determining the degree of hydrolysis of milk proteins.
in the measurement of free amino acids of milk samples by O-phthaldialdehyde/N-acetyl-L-cysteine (OPA/NAC) assay.
in the derivatization of putrescine samples.

Ortho-phtalaldehyde (OPA), an aromatic compound with two aldehyde groups, has been claimed to have an effective bactericidal character, having therefore been suggested as a replacement for glutaraldehyde, for high-level disinfection.
This FDA (Food and Drug Administration) approved biocide has several potential advantages comparing to glutaraldehyde: it is virtually odourless, stable, effective over a wide 3–9 pH range, non-irritant to the eyes and nasal passages, and does not require activation before its use.
Moreover, microorganisms that have acquired resistance to glutaraldehyde have not yet gained cross-resistance to OPA.
So far, toxic effects associated with amino acids interaction, and cellular cross-link, have commonly been used to explain the antimicrobial action of OPA .

However, specific mechanisms in the antimicrobial action of OPA, against Gram-negative bacteria, remain poorly characterized.
Some authors have stated that there is an urgent need to deeper investigate the nature of the inhibitory and lethal effects of both biocides and disinfectants.
This need emerges from the fact that the rise in the resistance to biocides might result in cross-resistance to other antimicrobial agents, especially at low concentrations.
A wide range of possible multi-target cell sites would therefore constitute an important aspect of such studies.
Previous reports have recognized OPA as being a multi-target biocide.
Thus, the chance for most bacterial cells to develop resistance to the in-use biocidal concentrations is unlikely.
At high concentrations, the toxic agent induces rapid kill of bacterial cells, through the implication of multi-target sites

Potential Exposure
The primary routes of human exposure to o-phthalaldehyde are by inhalation and through the skin, which may occur through accidental or occupational exposures.
Along with its increasing popularity as a chemical sterilizer, o-phthalaldehyde has many applications in analytical methods and in diagnostic kits.
o-Phthalaldehyde is also used as an intermediate in the synthesis of pharmaceuticals and as a reagent in the tanning industry, hair colorings, wood treatment, and antifouling paints.
o-Phthalaldehyde was approved for use as an indoor antimicrobial pesticide in 1997; however, it is no longer registered with the United States Environmental Protection Agency (USEPA) for this use.

Carcinogenicity
No information on the carcinogenicity of o-phthalaldehyde in experimental animals or humans was found in a review of the literature.

OPA is a relatively new aromatic dialdehyde antimicrobial agent.

Ortho‐phthalaldehyde: a possible alternative to glutaraldehyde for high level disinfection
S. Walsh, J. Maillard, A. Russell
Published 1999
Biology, Medicine
Journal of Applied Microbiology
Ortho‐phthalaldehyde (OPA) was tested against a range of organisms including glutaraldehyde‐resistant mycobacteria, Bacillus subtilis spores and coat‐defective spores.
Glutaraldehyde (GTA) and peracetic acid (PAA) were tested for comparative purposes.
Both suspension and carrier tests were performed using a range of concentrations and exposure times.
All three biocides were very effective (≥ 5 log reduction) against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa in suspension tests.
OPA and GTA (PAA was not tested) were also very effective against Staph. aureus and Ps. aeruginosa in carrier tests.
OPA showed good activity against the mycobacteria tested including the two GTA‐resistant strains, but 0·5% w/v OPA was found not to be sporicidal.
However, limited activity was found with higher concentrations and pH values.
Coat‐defective spores were more susceptible to OPA, suggesting that the coat may be responsible for this resistance.
The findings of this study suggest that OPA is effective against GTA‐resistant mycobacteria and that it is a viable alternative to GTA for high level disinfection. LESS

Is OPA the Same as Glutaraldehyde?
OPA, o-phthalaldehyde is one of the new replacements for glutaraldehyde in high level liquid disinfection.
OPA shares many chemical similarities to glutaraldehyde and has similar toxicity, but the lower vapor pressure reduce the smell and vapor concentrations.

Glutaraldehyde has been used used as a high level disinfectant in healthcare for decades, particularly for endoscopes and other immersible items that need to be disinfected and turned around quickly.
Glutaraldehyde is a very effective disinfectant but in recent years it has fallen out of favor because of eye, skin and respiratory irritation, sensitivity and occupational asthma. Glutaraldehyde has even been eliminated completely from use in the UK’s National health service.

There are two main classes of chemical used for high level disinfection, the aldehydes and the oxidizers.
The latter includes peracetic acid, hydrogen peroxide and sodium hypochlorite and the race has been on to find alternatives to glutaraldehyde.
Glutarladehyde is a dialdehyde, i.e. it has two aldehyde groups.
The aldehyde group is the -COH part of the molecule in organic chemistry.
There have been numerous complaints of irritation, sensitivity and occupational asthma from users of glutaraldehyde and substitutes have been sought.

The obvious substitutes are other dialdehydes such as OPA (shown below).
Other dialdehydes, such as succinic dialdehyde have also been considered as high level disinfectants however succinic dialdehyde is not on the FDA’s list of approved sterilants and disinfectants.
These dialdehydes generally have similar chemical properties to glutaraldehyde and function similarly.
Disinfection is achieved by their ability to cross link and hence inactivate proteins.

Glutaraldehyde
OPA

The most successful dialdehdyde substitute for glutaraldehyde is OPA which is now sold as a replacement for glutaraldehyde.
OPA has the advantage that it a solid compared to liquid glutaraldehyde, though both are normally supplied in solution, and so a OPA has lower vapor pressure and much less smell than the pungent glutaraldehyde.
In addition, OPA is more effective and so can be used at a lower concentration.

Glutaraldehyde and OPA are structurally similar and so have similar chemical properties.
On this basis similar occupational health effects have been anticipated.
The disinfection mechanism is similar and so similar health effects on exposure may be expected.
The lower vapor pressure of the OPA has reduced the irritation to the eyes and respiratory system and has greatly reduced the objection to the strong smell of glutaraldehyde.
However, as with glutaraldehyde, there have been reports of sensitization with OPA as well as occupational asthma and contact dermatitis.

The use of glutaraldehyde has increased in recent years in the US with the widespread adoption of automatic reprocessors for endoscopes.
This equipment significantly reduces the occupational exposure to the disinfectant.
Even so, workers can still be exposed and measures should be taken to minimize exposure.

As with handling any high level disinfection or sterilant chemical, the basic methods to increase workplace safety are as follows:
•   The reprocessor should be located in a well ventilated area, preferably with a local exhaust to remove any vapors that are released from the equipment.
•   A continuous gas monitor for the chemical used should be installed to provide a warning in case the concentration gets too high (leak, malfunction of the reprocessor, or ventilation).
Continuous gas monitors are available for peracetic acid and hydrogen peroxide from ChemDAQ.
For those compounds for which a continuous gas monitor is not available, regular air sampling should be performed where the operators work to check the vapor concentrations.
•   The operators should be provided with suitable personal protective equipment (PPE), including gloves, masks, and perhaps respirators depending on the circumstances.
•   The operators must be trained on the safe use of the chemicals and equipment they are using.
This training should include an understanding of the chemical hazards, how to recognize exposure if it occurs, and what they should do to prevent exposure.

Sources/Uses
Used as a disinfectant and in the fluorometric determination of primary amines and thiols; [Merck Index] Used to sterilize medical and dental equipment, as an enzyme inhibitor, indicator, chemical intermediate, diagnostic agent, tanning agent for leather, in water treatment, pulp and paper manufacturing, oil field water flooding, hair colorings, wood treatment, and antifouling paints; [NTP]

Synonyms
Phtalaldehydes [French]; Phthalaldehyde; Phthalic aldehyde; Phthalic dialdehyde; Phthalyldicarboxaldehyde; o-Phthaldialdehyde; 1,2-Benzenedicarboxaldehyde; [ChemIDplus] Cidex OPA; [Merck Index] OPA; 1,2-Benzenedialdehyde; 1,2-Diformylbenzene; 1,2-Phthalaldehyde; 2-Formylbenzaldehyde; o-Benzenedicarbaldehyde; Benzenedicarboxaldehyde; OP 100S; OP 100SF; o-Phthalic aldehyde; Phthalic dicarboxaldehyde; Phtharal; [NTP] UN2923

Ortho-phthalaldehyde (OPA) Overview.
Ortho-phthalaldehyde is a high-level disinfectant that received FDA clearance in October 1999.
It contains 0.55% 1,2-benzenedicarboxaldehyde (OPA).
OPA solution is a clear, paleblue liquid with a pH of 7.5.

Mode of Action.
Preliminary studies on the mode of action of OPA suggest that both OPA and glutaraldehyde interact with amino acids, proteins, and microorganisms.
However, OPA is a less potent cross-linking agent.

This is compensated for by the lipophilic aromatic nature of OPA that is likely to assist its uptake through the outer layers of mycobacteria and gram-negative bacteria.
OPA appears to kill spores by blocking the spore germination process.

Microbicidal Activity.
Studies have demonstrated excellent microbicidal activity in vitro.
For example, OPA has superior mycobactericidal activity (5-log10 reduction in 5 minutes) to glutaraldehyde.
The mean times required to produce a 6-log10 reduction for M. bovis using 0.21 % OPA was 6 minutes, compared with 32 minutes using 1.5% glutaraldehyde.
OPA showed good activity against the mycobacteria tested, including the glutaraldehyde-resistant strains, but 0.5% OPA was not sporicidal with 270 minutes of exposure.
Increasing the pH from its unadjusted level (about 6.5) to pH 8 improved the sporicidal activity of OPA.

The level of biocidal activity was directly related to the 48 Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008 temperature.
A greater than 5-log10 reduction of B. atrophaeus spores was observed in 3 hours at 35º C, than in 24 hours at 20º C.

Also, with an exposure time 10 minutes.
In addition, OPA is effective (>5-log10 reduction) against a wide range of microorganisms, including glutaraldehyde-resistant mycobacteria and B. atrophaeus spores.
The influence of laboratory adaptation of test strains, such as P. aeruginosa, to 0.55 % OPA has been evaluated.
Resistant and multiresistant strains increased substantially in susceptibility to OPA after laboratory adaptation (log10 reduction factors increased by 0.54 and 0.91 for resistant and multiresistant strains, respectively).

Other studies have found naturally occurring cells of P. aeurginosa were more resistant to a variety of disinfectants than were subcultured cells.

Uses.

OPA has several potential advantages over glutaraldehyde.

It has excellent stability over a wide pH range (pH 3–9), is not a known irritant to the eyes and nasal passages, does not require exposure monitoring, has a barely perceptible odor, and requires no activation.
OPA, like glutaraldehyde, has excellent material compatibility.

A potential disadvantage of OPA is that it stains proteins gray (including unprotected skin) and thus must be handled with caution.

However, skin staining would indicate improper handling that requires additional training and/or personal protective equipment (e.g., gloves, eye and mouth protection, and fluid-resistant gowns).

OPA residues remaining on inadequately water-rinsed transesophageal echo probes can stain the patient’s mouth.
Meticulous cleaning, using the correct OPA exposure time (e.g., 12 minutes) and copious rinsing of the probe with water should eliminate this problem.
The results of one study provided a basis for a recommendation that rinsing of instruments disinfected with OPA will require at least 250 mL of water per channel to reduce the chemical residue to a level that will not compromise patient or staff safety (5-log10 reduction in bacterial load.

Furthermore, OPA was effective over a 14-day use cycle 100.

Manufacturer data show that OPA will last longer in an automatic endoscope reprocessor before reaching its MEC limit (MEC after 82 cycles) than will glutaraldehyde (MEC after 40 cycles) 400.

High-pressure liquid chromatography confirmed that OPA levels are maintained above 0.3% for at least 50 cycles.

OPA must be disposed in accordance with local and state regulations.

If OPA disposal through the sanitary sewer system is restricted, glycine (25 grams/gallon) can be used to neutralize the OPA and make it safe for disposal.
The high-level disinfectant label claims for OPA solution at 20º C vary worldwide (e.g., 5 minutes in Europe, Asia, and Latin America; 10 minutes in Canada and Australia; and 12 minutes in the United States).
These label claims differ worldwide because of differences in the test methodology and requirements for licensure.
In an automated endoscope reprocessor with an FDA-cleared capability to maintain solution temperatures at 25º C, the contact time for OPA is 5 minutes.

March 25, 2022

By admin

Ortho-Phthalaldehyde (OPA)

Ortho-Phthalaldehyde (OPA)

Ortho-Phthalaldehyde (OPA)

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