Determination of o-phthalaldehyde for dose verification of the clinical disinfectant by fluorescent sequential injection analysis.

A new automated, generic analytical approach for determining the clinical disinfectant o-phthalaldehyde (OPA) is reported in this study. The proposed sequential injection analysis (SIA) is based on the online reaction of the OPA with glycine/N-acetylcysteine (NAC) in a neutral medium (pH = 7.0) to form a highly fluorescent isoindole derivative. All critical flow and reaction variables were investigated, while validation was carried out in the linearity detection range (0.0075-0.02%). As a result, excellent linearity (R2 > 0.99) and precision (1.5-2.4% for repeatability and 0.7-2.2% for reproducibility) were achieved for the reference OPA solutions. Furthermore, reasonable concentration verification of OPA disinfection (0.2-0.6%) in healthcare institutes can be achieved using the developed fluorescent SIA due to its good sensitivity (0.111 V/%) and precision (1.0-2.3% for intermediate precision) around the minimum effective concentration (MEC) of 0.3% for Cidex-OPA disinfectant.

An approach to quantify ortho-phthalaldehyde contamination on work surfaces.

Ortho-phthalaldehyde (OPA) is used as a high-level disinfectant for reusable medical devices in healthcare settings. The ACGIH recently adopted a Threshold Limit Value-Surface Limit (TLV-SL; 25 µg/100 cm2) for OPA surface contamination to prevent induction of dermal and respiratory sensitization following dermal exposure. However, there is no current validated method to measure OPA surface contamination. This study aimed to develop a standardized approach for sample collection and quantitative determination of OPA from work surfaces for use in risk assessment practices. The reported method utilises readily available commercial wipes to collect surface samples coupled with direct detection of OPA via liquid chromatography time of flight mass spectrometry (LC-ToF-MS). This approach avoided complex derivatization steps commonly required for the analysis of aldehydes. Method evaluation was conducted in accordance with the Occupational Safety and Health Administration (OSHA) surface sampling guidelines. Overall recoveries of 25 µg/100 cm2 of OPA from stainless steel and glass surfaces were 70% and 72%, respectively. The reported LOD for this method was 1.1 µg/sample and the LOQ was 3.7 µg/sample. OPA remained stable on the sampling medium for up to 10 days, when stored at 4 °C. The method was demonstrated in a workplace surface assessment at a local hospital sterilising unit, successfully detecting OPA on work surfaces. This method is intended to supplement airborne exposure assessment and provide a quantitative assessment tool for potential dermal exposure. When used in conjunction with a thorough occupational hygiene program that includes hazard communication, engineering controls, and personal protective equipment, skin exposure and consequent sensitization risks in the workplace can be minimized.

Characterization of Exposure to Cleaning Agents Among Health Workers in Two Southern African Tertiary Hospitals.

BACKGROUND: Whilst cleaning agents are commonly used in workplaces and homes, health workers (HWs) are at increased risk of exposure to significantly higher concentrations used to prevent healthcare-associated infections. Exposure assessment has been challenging partly because many are used simultaneously resulting in complex airborne exposures with various chemicals requiring different sampling techniques. The main objective of this study was to characterize exposures of HWs to various cleaning agents in two tertiary academic hospitals in Southern Africa. METHODS: A cross-sectional study of HWs was conducted in two tertiary hospitals in South Africa (SAH) and Tanzania (TAH). Exposure assessment involved systematic workplace observations, interviews with key personnel, passive personal environmental sampling for aldehydes (ortho-phthalaldehyde-OPA, glutaraldehyde and formaldehyde), and biomonitoring for chlorhexidine. RESULTS: Overall, 269 samples were collected from SAH, with 62 (23%) collected from HWs that used OPA on the day of monitoring. OPA was detectable in 6 (2%) of all samples analysed, all of which were collected in the gastrointestinal unit of the SAH. Overall, department, job title, individual HW use of OPA and duration of OPA use were the important predictors of OPA exposure. Formaldehyde was detectable in 103 (38%) samples (GM = 0.0025 ppm; range: <0.0030 to 0.0270). Formaldehyde levels were below the ACGIH TLV-TWA (0.1 ppm). While individual HW use and duration of formaldehyde use were not associated with formaldehyde exposure, working in an ear, nose, and throat ward was positively associated with detectable exposures (P-value = 0.002). Glutaraldehyde was not detected in samples from the SAH. In the preliminary sampling conducted in the TAH, glutaraldehyde was detectable in 8 (73%) of the 11 samples collected (GM = 0.003 ppm; range: <0.002 to 0.028). Glutaraldehyde levels were lower than the ACGIH's TLV-Ceiling Limit of 0.05 ppm. p-chloroaniline was detectable in 13 (4%) of the 336 urine samples (GM = 0.02 ng/ml range: <1.00 to 25.80). CONCLUSION: The study concluded that detectable exposures to OPA were isolated to certain departments and were dependent on the dedicated use of OPA by the HW being monitored. In contrast, low-level formaldehyde exposures were present throughout the hospital. There is a need for more sensitive exposure assessment techniques for chlorhexidine given its widespread use in the health sector.

Evaluation of the ceiling levels of ortho-phthalaldehyde exposure among health care workers engaged in endoscope disinfection: A new methodology using video-exposure monitoring.

OBJECTIVES: The present study aimed to develop a method for measuring the ceiling level of ortho-phthalaldehyde (OPA) exposure and evaluate the ceiling levels of OPA exposure among health care workers who handle disinfectant solutions containing OPA for the disinfection of endoscopes. METHODS: The study consisted of a preliminary survey and main survey. In the preliminary survey, processes involving high-concentration exposure to OPA were identified by video-exposure monitoring (VEM). In the main survey, the ceiling levels of OPA exposure for high-concentration exposure processes identified from the results of the preliminary survey were determined using a measuring method combining sampling using a 2,4-dinitrophenylhydrazine-silica cartridge and analysis by high-performance liquid chromatography tandem mass spectrometry. RESULTS: In the preliminary survey, seven processes involving high-concentration exposure to OPA were identified by VEM. The duration of each process was short, lasting from 20 seconds to a few minutes. In the main survey, the OPA concentrations for the identified high-concentration exposure processes ranged from 1.18 to 4.49 ppb, which markedly exceeded the threshold limit value ceiling (TLV-C) of 0.1 ppb recommended by the American Conference of Governmental Industrial Hygienists. CONCLUSIONS: The method for measuring the ceiling level of OPA exposure was established using VEM and the highly sensitive method of chemical analysis; and we successfully evaluated the ceiling levels of OPA exposure among health care workers engaged in endoscope disinfection. This approach can also be applied to other chemical substances with recommended TLV-Cs, and important information for reducing exposure can thus be obtained.

Development of a measurement method to determine the ceiling exposure concentration of ortho-phthalaldehyde handling workers.

OBJECTIVES: The purpose of this research was to develop and validate an analytical method for rapid determination of the exposure of workers to ortho-phthalaldehyde (OPA) at the ceiling threshold concentration. METHODS: A 2,4-dinitrophenylhydrazine (DNPH)-silica cartridge was chosen as a sampler. OPA collected by the DNPH-silica cartridge was subsequently extracted with 5 mL of acetonitrile. A 50-µL aliquot of phosphoric acid/acetonitrile solution (2%, v/v) was added to 950 µL of the extraction solution and allowed to stand for 30 minutes at room temperature. This solution was then analyzed by high-performance liquid chromatography tandem mass spectrometry. The basic characteristics of the proposed method, such as recovery, repeatability, limit of quantification, and storage stability of the samples, were examined. RESULTS: The overall recoveries of OPA from OPA-spiked DNPH-silica cartridges were 93.6%-100.1% with relative standard deviations, representing the repeatability, of 1.5%-10.8%. The limit of quantification was 0.165 ng/sample. The recovery of OPA from DNPH-silica cartridges after 5 days of storage in a refrigerator exceeded 95%. CONCLUSIONS: The proposed method enabled the determination of the OPA concentration corresponding to the Threshold Limit Value-Ceiling of 0.1 ppb recommended by the American Conference of Governmental Industrial Hygienists, with a minimum sampling time of 18 seconds (corresponding to a sampling volume of 300 mL at 25°C and 1 atm). Thus, this method will be useful for estimating worker exposures to OPA.

Spectrofluorometric Determination of Putrescine: Optimization of the Putrescine-Orthophthaldehyde Complex Using Spectrofluorometry.

In alkaline medium, the complex formed between putrescine and orthophthalaldehyde was studied using spectrofluorescence. The derivative is kinetically stable 24 h after complexation. The stoichiometry of the complex is 1:1 at maximum fluorescence intensity, also 24 h after complexation.

[Simultaneous determination of o-phthalaldehyde, p-chloro-m-xylenol and triclosan in compound chemical disinfectants and daily chemicals by micellar electrokinetic chromatography].

A novel method for the separation and determination of o-phthalaldehyde (OPA), p-chloro-m-xylenol (PCMX) and triclosan in daily chemicals and compound chemical disinfectants in a single run by micellar electrokinetic chromatography (MEKC) was established. The factors such as the buffer concentration and pH, the concentration of sodium dodecyl sulfate (SDS), and the sample buffer, were investigated in detail. The analysis was carried out using a 50 microm uncoated capillary of 40.2 cm in total length (effective length: 30 cm). The running buffer was 20 mmol/L Na2B4O7, and 80 mmol/L SDS. The sample buffer was 2 mmol/L Na2B4O7-8 mmol/L SDS (without pH adjustment) containing 10% (v/v) methanol. The detection wavelength was 214 nm. The relative standard deviations (RSDs) of the corrected peak areas of the three components were in the range of 1.1% - 3.8%, and the RSDs of migration times were less than 0.9%. The limits of detection (LODs, S/N = 3) were 4.0, 0.4 and 0.4 mg/L, and the limits of quantification (LOQs, S/N = 10) were 12, 1.2, and 1.2 mg/L for OPA, PCMX and triclosan, respectively. The corrected peak areas and the concentrations of the three components showed good linear relationship within the ranges of 12 - 2 000 mg/L, 1.2 - 200 mg/L and 1.2 - 200 mg/L with the correlation coefficients of 0.999 4, 0.999 3 and 0.999 5 for OPA, PCMX and triclosan, respectively. The method was used for the determination of the three components in compound chemical disinfectants, hand washing liquids, soaps and a toothpaste. The results showed that the three components could be assayed in a single run with simple sample pretreatment, rapidity, accuracy and low cost, and the method is convenient for routine analysis.

Determination of ortho-phthalaldehyde in water by high performance liquid chromatography and gas chromatography-mass spectrometry after hydrazine derivatization.

A simple high performance liquid chromatographic (HPLC) method and a highly sensitive gas chromatography mass spectrometric (GC-MS) method have been established for the determination of ortho-phthalaldehyde (OPA) in water. These methods are based on the derivatization of OPA with hydrazine in water. The following optimum reaction conditions were established: reagent dosage, 20 mg/mL of hydrazine; pH 2; reaction for 20 min at 70 °C. The organic derivative was detected directly by HPLC or after the extraction with methylene chloride/concentration by GC-MS. The limit of detection of OPA in water was 4.0 and 0.3 µg/L by HPLC and GC-MS, respectively. The calibration curve showed good linearity with r² = 0.9993 and r² = 0.9994 by HPLC and GC-MS, respectively, the accuracy was in a range of 95-105%, and the precision of the assay was less than 13% in water. The HPLC method was simple and reproducible enough to permit the OPA content analysis in the disinfectant products, and the GC-MS method is sensitive enough to permit reliable analysis of OPA to the µg/L level in environmental water.

Determination of fumonisins B1 and B2 in maize food products by a new analytical method based on high-performance liquid chromatography and fluorimetric detection with post-column derivatization.

A sensitive and selective analytical method for the quantitative determination of fumonisins B(1) (FB(1)) and B(2) (FB(2)) in maize-based foods for direct human consumption is described. The method, based on high-performance liquid chromatography and fluorescence detection, presents a rapid and automated online post-column derivatization, performed with o-phthalaldehyde and N,N-dimethyl-2-mercaptoethylamine (Thiofluor™). A complete separation of fumonisins is achieved in less than 13 min by using a C18 column and a gradient elution. Fumonisins are extracted from the sample with a mixture of water, acetonitrile, and methanol. The filtered extract is purified by immunoaffinity column and FB(1) and FB(2) are eluted with methanol. The method has been successfully validated, and performances comply with -criteria of the Regulation EC No 401/2006.

A microchip electrophoresis strategy with online labeling and chemiluminescence detection for simultaneous quantification of thiol drugs.

An integrated microfluidic device with online labeling and chemiluminescence (CL) detection was developed for the simultaneous quantification of thiol drugs. In this device, the online labeling, electrophoresis separation and CL detection were compactly integrated onto a glass/poly(dimethylsiloxane) (PDMS) hybrid microfluidic chip. CL detection was based on the oxidation reaction of N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and o-phthalaldehyde (OPA) labeled thiol drugs with NaBrO. Four thiol drugs including 2-mercaptopropionylglycine (2-MPG), captopril (CP), 6-thioguanine (6-TG) and 6-mercaptopurine (6-MP) were employed as model compounds to examine the utility of the system. It was indicated that the separation and detection of four drugs can be completed within 90s. Detection limits (S/N=3) for the thiol drugs tested were in the range of 8.9×10(-9)-13.5×10(-9)M. The application of the present system was demonstrated by analyzing the thiol drugs in human plasma samples.

A measurement method for atmospheric ammonia and primary amines based on aqueous sampling, OPA derivatization and HPLC analysis.

A method of precolumn derivatization HPLC with fluorescence detection has been developed for the measurement of ammonia, primary methylamine, ethylamine, propylamine, and butylamine in the atmosphere. Air samples were collected by two continuously wetted glass frit/coil samplers, one directly from ambient air for the sum of gaseous and aerosol species, and the other after an acid-coated annular denuder for the aerosol species. The collection efficiency for all analytes was found to be > or = 99% at a sampling gas flow rate of 2 L min(-1) and a scrubbing water flow rate of 0.24 mL min(-1). The collected ammonia and primary amines were derivatized with o-phthalaldehyde (OPA) and n-acetyl-cysteine (NAC) reagents in an in-line derivatization coil to form highly fluorescent sulfonatoisoindole derivatives. Detailed kinetic study showed that derivatization reactions were fast but the derivatives were not very stable. Derivatization conditions, such as reagent concentrations, derivatication medium pH, and derivatization time, were optimized to achieve maximum derivative yields for all the analytes. The derivatives were separated on a C-18 reverse-phase column using a gradient elution and detected by a fluorescence detector at an excitation wavelength of 330 nm and an emission wavelength of 471 nm. The respective lower detection limits for ammonia and for the four primary amines were 24 parts per trillion by volume (pptv) and < or = 3 pptv, with a sample time resolution of about 1 min and a sampling/ analysis time of 20 win per cycle. The analytical methodology has been applied in the field measurements; results from two case studies are presented.

Determination of ortho-phthalaldehyde in air and on surfaces.

Three sampling and analytical methods have been developed and evaluated for ortho-phthalaldehyde (OPA): (1) an HPLC-UV method for OPA in air, (2) a fluorimetric method for OPA on surfaces, and (3) a colorimetric method for OPA on surfaces. (1) The air sampler contains 350 mg of silica gel coated with 1 mg of acidified 2,4-dinitrophenylhydrazine (DNPH). Air sampling may be conducted at 0.03 to 1.0 L min(-1) for periods up to 8 h. Samples were eluted with ethyl acetate, and the eluents were allowed to stand for 72 h. Analysis was by high performance liquid chromatography (HPLC) with a UV detector set at 369 nm. An unusual phenomenon was the observation that the stability of the sample on a sampler at 3 degrees C tends to decrease as the total quantity of OPA collected on the sampler decreases. Elution of the samples within 24 h of air sampling is required. The detection limit (LOD) is approximately 0.02 microg of OPA per sample. OPA on surfaces may be collected with strips cut from a sheet of polyvinyl alcohol (PVA wipe). (2) In the surface wipe method with analysis by fluorescence measurement, the strips of PVA wipe were placed into dimethyl sulfoxide. An aliquot was treated with aqueous N-acetyl-l-cysteine and ethylenediamine. Analysis was performed with a portable fluorometer (excitation and emission wavelengths = 365 nm and 438 nm, respectively). The LOD is 0.2 microg per sample. (3) In the surface wipe method with visual colorimetric detection, the strips of PVA wipe were placed into 30 : 70 acetonitrile : water. An aliquot was treated with N-(1-naphthyl)ethylenediamine in 0.1 m sulfuric acid. After color development, the LOD is approximately 48 microg per sample. These methods have been field tested in a hospital.

Photodecomposition of o-phthaldialdehyde-derivatized amino acids by the photodiode array detector during their high-performance liquid chromatographic analysis.

During the high-performance liquid chromatographic (HPLC) analysis of o-phthaldialdehyde (OPA)-derivatized amino acids such as arginine and homoarginine, we observed that the response of the fluorescence detection (FLD) system is decreased when the photodiode array detection (DAD) system (located before the FLD system) was simultaneously switched on. The decrease in the FLD response, i.e., the difference in the FLD peak area (DeltaA) obtained with DAD modes off (A(off)) and on (A(on)) was dependent upon the flow rate, but the relative FLD response decrease (DeltaA/A(off)) was practically independent of the amount of analyte injected. For example, decreasing the flow rate from 1 to 0.5 mL/min resulted in the relative decrease of FLD response from approximately 5% to 11%. It was concluded that DAD caused a photoinduced partial decomposition of the OPA-derivatized amino acids flowing through the cell. The photoinduced dissociation of OPA derivatives was independently supported by using off-line photodiode array spectrometric measurements with long and short irradiation pulses. Based on the experimental results, for description of the variation of FLD responses with the flow rate upon the irradiation by DAD a simple mathematical model is proposed and reported.

Fluorescent method for detection of cleaved collagens using O-phthaldialdehyde (OPA).

Analysis of collagen degradation remains an important but cumbersome task. Traditional methods with dansyl chloride derivatization of collagen have been used to quantify collagen damage. Fluorescent labeling reagents have been developed that offer advantages such as greater solubility in water and low background emission. One such reagent is o-phthalaldehyde (OPA). In this study, we used OPA as a means of detecting small amounts of degraded collagen. Collagen samples isolated from skin or heart were used for OPA conjugation to exposed amino termini ("opalation"). Experiments utilizing small samples aliquoted in microtiter plates were performed to evaluate effects of increasing concentrations of OPA, varying concentrations of collagen, and effects of matrix metalloproteinase (MMP) digestion. Results indicate that within 10 min of reaction, OPA can be used to detect relative differences in cleaved vs. uncleaved collagen from skin or heart. Heart samples obtained from regions of high MMP activity correlated with increased OPA fluorescence relative to tissue with lower MMP activity. On the basis of these results, we conclude that OPA has valuable practical advantages for analytical use in detecting cleaved collagen in small tissue samples.

Advances in the o-phthalaldehyde derivatizations. Comeback to the o-phthalaldehyde-ethanethiol reagent.

The main aims of this work were (a) to present the characteristics and stability of the o-phthalaldehyde (OPA)-ethanethiol (ET) derivatives of 22 amino acids, including the believed-to-be less stable OPA derivatives providing glycine, gamma-aminobutyric acid, beta-alanine, histidine, ornithine, lysine and the C(1)-C(5) aliphatic amines; (b) to compare the stability properties of the most common amino acids and amines as OPA-ET-fluorenylmethyl chloroformate (FMOC) derivatives to the corresponding ones obtained from OPA reagents containing various (SH)-additives; (c) to show the molar responses of alanine and lysine depending on the OPA reagent's composition; as well as (d) to prove the practical utility of these basic researches, by the simultaneous HPLC separation of 22 amino acids and 15 amines as their OPA-ET-FMOC derivatives. Investigations have been carried out by varying the composition of the reagents, the molar ratios of reactants and the reaction time, applying diode array and fluorescence detections simultaneously. Average reproducibility of quantitations, characterized with the relative standard deviations (RSDs) based on the fluorescence intensities of derivatives, in the order of listing, proved to be 1.2-5.9% for amino acids and 1.1-8.7% for amines. The practical utility of the method is demonstrated by the analysis of the amino acid and amine contents of mouse tissues, with an average reproducibility of 3.5%.

Efectividad y seguridad del ortoftalaldehído en la desinfección de alto nivel de material sanitario: una revisión sistemática / No disponible

El ortoftalaldehdo (OPA) al 0,55% es un desinfectante de alto nivel que constituye una alternativa al glutaraldeho­do al 2% en la desinfección de material semicrí­tico. Objetivos: Evaluar la efectividad y seguridad del OPA al 0,55% en la desinfección de alto nivel de material sanitario. Comparar el OPA con otras alternativas disponibles para la desinfección de alto nivel, en términos de costes y/o coste-efectividad. Métodos: Revisión sistemática. Resultados: Cinco estudios primarios cumplieron los criterios de inclusión y se seleccionaron. Los artículos mostraron que el OPA era una alternativa efectiva para la desinfección de alto nivel de endoscopios. En algunos pacientes diagnosticados de cáncer de vejiga y sometidos a cistoscopias de repetición, la desinfección del instrumental urológico con OPA se asoció con la aparición de reacciones anafilácticas/hipersensibilidad. Conclusiones: Es necesario realizar estudios sobre la efectividad, costes-efectividad y seguridad del OPA frente a la mejor alternativa disponible en la desinfección de alto nivel (AU)

To evaluate the effectiveness and safety of 0,55% OPA for high level disinfection of medical devices. To compare OPA against other alternatives available for high level disinfection, in terms of cost and/or cost effectiveness. Methods: Systematic review. Results. Five original articles met the inclusion criteria and were selecteed. Papers showed that OPA was an effective alternative as high level disinfectant for endoscopes. In some bladder cancer patients undergoing repeated cystoscopies OPA was associated with "anaphylaxis-like" reactions. Concluisons: Studies that assess the effectiveness, cost- effectiveness and safety are necessary to compare ortho-phthaleldehyde with the best avaible alternative for high level disinfection (AU)

Determination of orthophthalaldehyde in air using 2,4-dinitrophenylhydrazine-impregnated silica cartridge and high-performance liquid chromatography.

A new method is described for the determination of orthophthalaldehyde in air which is used for the disinfection of various instruments (e.g. endoscopes) in hospital. Orthophthalaldehyde in air was collected with a silica gel cartridge impregnated with acidified 2,4-dinitrophenylhydrazine (DNPH-cartridge) and derivatives were analyzed by high-performance liquid chromatography (HPLC). In this study, the derivatization was examined by comparing the process with three phthalaldehyde isomers (ortho-, iso- and tere-). In the case of iso- and tere-phthalaldehyde, derivatives synthesized with excess of aldehyde consisted mainly of mono-derivatives, and derivatives synthesized with excess of DNPH consisted mainly of bis-derivative. In the case of orthophthalaldehyde, derivative consisted of only bis-derivative and mono-derivative was never observed under any conditions. Orthophthalaldehyde was completely retained by the DNPH-cartridge during air sampling, however, the derivatization reaction was incomplete and unreacted orthophthalaldehyde was flushed from the cartridge during the subsequent solvent extraction process. Unreacted orthophthalaldehyde and DNPH reacted again in the extraction solvent solution. Immediately after the solvent extraction, both mono- and bis-DNPhydrazone derivatives of orthophthalaldehyde were present in the solution. However, over time, the mono-derivative decreased and bis-derivative increased until only the bis-derivative was left allowing accurate determination of the orthophthalaldehyde concentration. The transformation of mono-derivative to bis-derivative was faster in polar aprotic solvents such as acetonitrile, dimethyl sulfoxide and ethyl acetate. Transformation was found to occur most quickly in acetonitrile solvent and was completed in 4 h in this case. It was possible to measure orthophthalaldehyde in air as bis-derivative using a DNPH impregnated silica cartridge and HPLC analysis.

Improved method for the determination of anatoxin-a and two of its metabolites in blue-green algae using liquid chromatography with fluorescence detection.

Anatoxin-a, a neurotoxin produced by blue-green algae (BGA) species, can cause death to exposed organisms. In North America, BGA are harvested and sold as food supplements, some of which contain elevated levels of other algal toxins, such as microcystins. Concern that elevated levels of anatoxin-a also may be present in BGA food supplements has led to the development of a simple method to determine the presence of anatoxin-a in BGA. Some researchers have successfully analyzed this compound using liquid chromatography with fluorescence detection by forming a fluorescent derivative with 4-fluoro-7-nitrobenzofurazan (NBD-F) in water and phytoplankton extracts. With this method, the background noise is high in BGA extracts due to the presence of co-extractives. Addition of o-phthaldialdehyde (OPA) and mercaptoethanol to the extract before addition of the NBD-F resulted in the successful removal of primary amines from the background noise when the NBD-F derivatives were detected with fluorescence. Improved chromatograms were obtained when extracts were cleaned up in this manner, leading to a lower detection limit (approximately 50 microg/kg) for anatoxin-a. The detection limits obtained for the 2 degradation products dihydroanatoxin-a and epoxyanatoxin-a in BGA extracts were similarly low (55 and 65 microg/kg, respectively).

[Study of direct fluorophotometric and flow-injection fluorophotometric methods based on the inhibitory effect for the determination of trace formaldehyde].

Sulfite reacts with o-phthalaldehyde in the presence of ammonium forming the highly fluorescing isoindole-1-sulfonate in neutral or weakly acid solution, and formaldehyde has inhibitory effect on it. Based on this principle, the authors developed the direct fluorophotometric and flow-injection fluorophotometric methods for the determination of trace formaldehyde. The maximum excitation wavelength and the maximum emission wavelength are 320 and 390 nm respectively. With the direct fluorophotometric method, formaldehyde in the concentration range of 0.10-1.60 microg x mL(-1) can be determined with a detection limit of 0.046 microg x mL(-1). With the flow-injection fluorophotometric method, formaldehyde in the concentration range of 0.10-2.00 microg x mL(-1) can be determined with a detection limit of 0.085 microg x mL(-1). The methods were applied respectively to the analysis of river water with satisfactory results.