Enhancement of anti-cholinesterase activity of aqueous samples by hypochlorite oxidation for monitoring traces of organophosphorus pesticides in water

Effect of hypochlorite oxidation on cholinesterase-inhibition assay of acetonitrile extracts from fruits and vegetables for monitoring traces of organophosphate pesticides

“…The inhibition curves also were in good agreement with those of their oxidative standards, except for the chlorinated isoxathion solution. These observations suggest that the main products observed for the chlorpyrifos-, diazinon-, and fenitrothion-hypochlorite reactions were their oxygen analogues (Kanno et al, 2012). However, further chlorination of the isoxathion-hypochlorite reaction has been shown to produce the unknown compound(s) (Onodera et al, 1992;Kanno et al, 2012) in the chlorinated water (100 mg/l as active chlorine) even at pH 6.0 for 15 min.…”

“…It is also important to discern how the distribution of oxidation products varies with experimental conditions, such as hypochlorite oxidation and ChE-inhibiting assays. Our previous papers (Onodera et al, 1992;Kanno et al, 2012) revealed that excess hypochlorite in water at pH 7.0 oxidised the P=S pesticides stoichiometrically within 5 min into their P=O analogues. The resulting products were comparatively stable in water at low concentrations of active chlorine (less than 100 mg/l) in an acidic solution of pH 6.0.…”

“…A sample volume of 1 μl was splitlessly injected into the GC-MS at 270°C. The confirmation and determination of organophosphorus and carbamate pesticides tested in the present study were carried out according to the methods described in previous papers (Kawakami et al, 2008;Kanno et al, 2010Kanno et al, , 2012.…”

“…3). In the first step of these reactions, two peaks corresponding to the original material and its oxon were observed on the chromatograms that were obtained from most of the tested compounds with the P=S moiety, and one peak corresponding to the compounds' oxons; these formed the main intermediates (Kanno et al, 2012). However, no peaks were observed on the chromatograms that corresponded to further oxidation products from the isoxathion-hypochlorite reactions, in spite of higher ChE-inhibition activity for the chlorinated isoxathion solutions, as can be seen in Fig.…”

“…In order to provide greater insight into the possible role of organic compounds in the formation of chlorinesubstituted or chlorine-oxidised compounds and chlorineinduced mutagens, our laboratory has further explored the study of the aqueous chlorination chemistry of organic compounds (Onodera, 2010;Kanno et al, 2010Kanno et al, , 2012. In the present study, we studied the chlorination conditions of the anti-cholinesterase inhibitors, organophosphothionate and carbamate pesticides in the acetonitrile extracts of fruits and vegetables, and developed a combination method of hypochlorite oxidation and ChE-inhibiting assays to monitor traces of these contaminants in apple, tomato, cucumber and strawberry.…”