Organophosphoric acid pesticides

A few brief notes are added on phosphorofluoridates even though their destruction by microbial activity — although clearly possible — may be limited by their toxicity to the requisite microorganisms. One of the motivations for their inclusion is the fact that the hydrolytic enzyme(s) responsible for defluorination — organophosphorous acid anhydrase (OPA) — is widespread, and is found in a number of bacteria (Landis and DeFrank 1990). The microbial hydrolysis of organophosphorus pesticides and cholinesterase inhibitors is accomplished by several distinct enzymes, all of which are termed organophosphorus acid anhydrolases. These have been reviewed (DeFrank 1991) so that only a few additional comments are justified. 

The phosphoric acid triesters (organophosphates, not to be mistaken for organophosphorous pesticides) are, like phthalates, plasticizers mixed into polymers to increase flexibility and workability. Unlike phthalates they are remarkable flame retardants as well. The total European production of phosphorous-base flame... 

The use of protein-coated acoustic wave devices for detection of gas-phase species has also been reported with claims of good sensitivity and selectivity. Guilbault et al. reported TSM sensors for the reversible gas-phase detection of formaldehyde [227], and organophosphorous pesticides [228,229]. More recent studies have cast some doubt as to whether the gas-phase sensitivity was the result of selective immunochemical binding, or simply due to nonspecific adsorption. In work reported by Thompson et al. [230], sensors coated with parathion antibody exhibited sensitivities to the pesticides parathion, malathion, and disul-foton that were remarkably similar to sensors coated with nonspecific proteins (valproic acid antiserum, human immunoglobulin G, and bovine serum albumin). The fact that the previous study [228] reported significantly larger sensitivity at... 

On-line SPE via valve-switching techniques, pioneered by the group of Brinkman [80], is frequently used in the enviroiunental analysis of aqueous samples, as it enables the rapid treatment of large samples. The precolumn enables selective sorption of the analytes, removal of hydrophihc interferences, and significant analyte preconcentration. In most cases, either 1-10 mm x 2-4.6 mm ID SPE cartridges packed with 30-50 pm ID particles are used. Typical applications of on-hne SPE-LC-MS are the determination of acidic herbicides [41], sidfonylureas [49], and organophosphorous pesticides [30]. Instead of SPE cartridges, Empore disks can be used on-line as well [79]. 

In agriculture, phenolic compounds are used as pesticides (Figure 1) and can also form from the degradation of chlorinated phenoxycarboxylic acids and organophosphorous insecticides". The herbicide DNOC sorption in a sandy aquifer (Denmark) has been reported ". 

The cholinesterase reaction (hydrolysis of a cholinester into choline and the corresponding carboxylic acid) is known to be inhibited by organophosphorous pesticides. The decrease in the activity of the cholinesterase can be measmed by means of a potentiometric choline electrode with molecular transduction using reduction of H2O2 by means of horseradish peroxidase [205, 206]. 

In the field of solid-phase extraction (SPE) methods, research is oriented toward the identification and synthesis of new sorbents with increased selectivity. It has already been shown that polar adsorbents such as Oasis HLB (vinylpyrrolidone-divinylbenzene copolymer) can isolate organophosphorous pesticides from blood or serum, or triazines, acetamides and phenoxy acids from surface and waste water. Recently, a new polymeric material, polyaniline, was introduced for the extraction of chlorophenolic pesticides in water samples. Immunosorbents produced by covalent immobilization of the antibody generated against the target analyte on... 

There are many studies available concerning the characterization of interface and ionization performance for the thermospray LC-MS analysis of pesticides, herbicides and insecticides, the improvement of detection limits and information content of the mass spectra. Compound classes most frequently studied are the carbamates, organophosphorous pesticides, triazine and phenylurea herbicides, chlorinated phenoxy acetic acids, and sulphonylureas. 

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