Detection organophosphate

Suggest an enzyme electrode-based procedure for detecting organophosphate pesticides. 

Polhuijs, M., Langenberg, J.P., Benschop, H.P. (1997a). A new method to detect organophosphate exposure serum analysis of victims of Japanese terrorists. In m-CB Medical Treatment Symposium, May 26-30, 1997, Hradec Kralove, Abstracts, p. 25. 

Booth, L.H., Hodge, S. and O Halloran, K. (2000) Use of cholinesterase in Aporrectodea caliginosa (Oligochaeta Lumbricidae) to detect organophosphate contamination comparison... 

A quartz plate equipped with a gold electrode on each face can detect the adsorption of mercury vapor on the gold. A carbon monoxide sensor can therefore be constructed since this gas reacts with mercury oxide at 210 liberating mercury vapor [224] which is detectable with the piezoelectric sensor. Similarly, the deposition of copper complexes on a quartz crystal is used to detect organophosphates [225] such as diisopropylmethylphosphonate (DIMP), and modified cyclodextrins are us to detect benzene vapors [226]. The piezoelectnc sensor is also used in the liquid phase to monitor the viscosity of fluids and gelation, and deduce, for example, the concentration of fibrinogen [227]. 

FosterRL. 1974. Detection and measurement of ambient organophosphate pesticides. ProcAnnuInd Air Pollut Control Conf 4 66-98. 

TharrD. 1998. Rapid assessment of organophosphate-induced cholinesterase depression A comparison of laboratory and field kit methods to detect human exposure to organophosphates. Appl Occup Environ Hyg 13 265-268. 

Undeger U, Institoris L, Siroki O, et al. 2000. Simultaneous geno- and immunotoxicological investigations for early detection of organophosphate toxicity in rats. Ecotoxicol Environ Saf 45 43-48. 

Chohnesterase-inhibiting pesticides (e g., organophosphate and carbamate pesticides) are detected by dipping the developed chromatogram in a solution of the enzyme chohnesterase followed by incubation for a short period. Then the plate is dipped in a substrate solution, e.g., 1-naphthyl acetate/fast blue salt B. In the presence of the active enzyme, 1-naphthyl acetate is hydrolyzed to 1-naphthol and acetic acid, and the 1-naphthol is coupled with fast blue salt B to form a violet-blue azo dye. The enzyme is inhibited by the pesticide zones, so the enzyme-substrate reaction does not occur pesticides are, therefore, detected as colorless zones on a violet-blue background [36]. 

Fournier E. Sonnier, M, Dally S (1978) Detection and assay of organophosphate pesticides in human blood by gas chromatography. Clin Toxicol 12 457-462. 

Hydraulic fluids themselves cannot be measured in blood, urine, or feces, but certain chemicals in them can be measured. Aliphatic hydrocarbons, which are major components of mineral oil hydraulic fluids and polyalphaolefin hydraulic fluids, can be detected in the feces. Certain components of organophosphate ester hydraulic fluids leave the body in urine. Some of these fluids inhibit the enzyme cholinesterase. Cholinesterase activity in blood can be measured. Because many other chemicals also inhibit cholinesterase activity in blood, this test is not specific for organophosphate ester hydraulic fluids. This test is not available at most doctor s offices, but can be arranged at any hospital laboratory. See Chapters 2 and 6 for more information. 

No data were located regarding absorption in animals after inhalation exposure to organophosphate ester hydraulic fluids or specific organophosphate esters, except for the observation that parent material was not detected by gas chromatography in the blood or urine of male rats exposed to 5,120 mg/m3 of an aerosol of a cyclotriphosphazene (99.9%) hydraulic fluid for 4 hours, thereby suggesting that the extent of absorption was limited (Kinkead and Bashe 1987). Blood samples were collected at 0, 24, and 48 hours after exposure was terminated. Urine was collected for 24 hours after exposure. 

A component of Skydrol 500B and Skydrol LD (tributyl phosphate) was detected in the air at the CP air test facility at Vancouver International Airport at a concentration of 0.04-0.3 mg/m3 (Labour-Canada 1990), indicating that organophosphate ester hydraulic fluids maybe released during aircraft maintenance operations on equipment using organophosphate ester hydraulic fluids. 

Organophosphate ester hydraulic fluid components have also been detected in groundwater near a hazardous waste site (1.7 pg/L tributyl phosphate) (Sawhney 1989) and in surface water from a radioactive waste disposal site (triphenyl phosphate and tributyl phosphate) (Francis et al. 1980). Organophosphate... 

Organophosphate ester components of hydraulic fluids such as triphenyl phosphate, nonylphenyl diphenyl phosphate, and cumylphenyl phosphate also have been detected in fish concentrations of 0.1-0.9 pg/g of fish tissue were detected principally near manufacturing facilities, while fish caught in other areas generally had concentrations below the detection limit (0.1 pg/g) (Mayer et al. 1981). In a market basket survey, tributyl phosphate was found to be present in 2% of the foods analyzed between April 1982 and April 1984 (Gunderson 1988). Intakes of tributylphosphate were estimated to be a maximum of 38.9 ng/kg body weight/day for 6- to 11-month-old children. 

Similarly, organophosphate esters are used in a wide variety of applications including hydraulic fluids, plasticizers, and antiwear additives to hydraulic fluids and engine oils. All of these uses have the potential to contaminate the environment, and all of the organophosphate ester components present in hydraulic fluids also are present in plasticizers and antiwear additives. Therefore, detection of a particular organophosphate ester in the environment or in biological media cannot identify the source of the contamination (i.e., hydraulic fluids, plasticizers, antiwear additives). 

Water samples are acidified and extracted with solvent (Kawamura and Kaplan 1983 Muir et al. 1981). Clean-up steps may be used (Kawamura and Kaplan 1983). Methylene chloride is often used as the extracting solvent, and it may interfere with the nitrogen-phosphorus detector. In this case, a solvent-exchange step is used (Muir et al. 1981). Analysis by GC/NPD or GC/MS provides specificity (Kawamura and Kaplan 1983 Muir et al. 1981). Accuracy is acceptable (>80%), but precision has not been reported. Detection limits were not reported, but are estimated to be 0.05-0.1 pg/L (Muir et al. 1981). Detection limits at the low ppt level (ng/L) were achieved by concentrating organophosphate esters on XAD-2 resin. The analytes were solvent extracted from the resin and analyzed by GC/NPD and GC/MS. Recovery was acceptable (>70%) and precision was good (<10% RSD) (LeBel et al. 1981). 

Organophosphate Ester Hydraulic Fluids. The measurement of organophosphate esters in fish and human adipose tissue has been used to assess environmental contamination in several studies (Mayer et al. 1981). The methods are able to detect concentrations of 0.1 mg/kg in fish and 2.5 pg/kg in human adipose... 

Enzymes can be used not only for the determination of substrates but also for the analysis of enzyme inhibitors. In this type of sensors the response of the detectable species will decrease in the presence of the analyte. The inhibitor may affect the vmax or KM values. Competitive inhibitors, which bind to the same active site than the substrate, will increase the KM value, reflected by a change on the slope of the Lineweaver-Burke plot but will not change vmax. Non-competitive inhibitors, i.e. those that bind to another site of the protein, do not affect KM but produce a decrease in vmax. For instance, the acetylcholinesterase enzyme is inhibited by carbamate and organophosphate pesticides and has been widely used for the development of optical fiber sensors for these compounds based on different chemical transduction schemes (hydrolysis of a colored substrate, pH changes). 

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