Effects of selected ionic liquids on the efficiency of CPO oxidation of methyl-parathion were studied. In general, the activity of CPO decreases with the increased concentration of ionic liquid. For ionic liquids with the same cation, those with PF 6 -exhibit strongest inhibition toward CPO, while those with either BF 4 -or metSO 4 -show relatively lesser inhibition. It was further demonstrated that even for buffer solutions containing up to 30% concentration of ionic liquids such as EAN, BMIMmetSO 4 , and EtPyTFA, CPO still can retain high activity (70-100% compared to that in citrate buffer) for oxidation of methylparathion. Photothermal enhancement factors of 3.5 times and corresponding improvements of sensitivity in the determination of organophosphates by the FIA-TLS method are predicted in 30% ionic liquids.
Photodegradation of coumaphos and azinphos-methyl in the air, in oxygen, and in nitrogen atmosphere (quartz reactor equipped with six 18-W lamps with the maximum emission intensity at 310 nm) was studied. The fastest reaction occurred with coumaphos in nitrogen atmosphere (complete decomposition in 10 min), where the formation of a new compound was also detected by high-performance liquid chromatography (HPLC). In the case of azinphos-methyl, no additional signals in HPLC chromatogram were observed. The rearrangement mechanism, involving a triplet-state activation complex and the formation of an acetylcholinesterase (AChE)-inhibiting oxo analog of coumaphos was verified and confirmed by laser flash photolysis.The suitability of bioanalytical flow-injection analysis (FIA) systems, based on AChE inhibition and spectrophotometric or thermal lens spectrometric detection for rapid and sensitive screening in food quality control was demonstrated. Owing to the high sensitivity of thermal lens spectrometry (TLS), several steps in sample preparation can be avoided (preconcentration, purification, isolation) and incubation times reduced. High sample throughputs (10 h -1 ) are, however, also achievable for medium toxic oxo organophosphorus (OP) pesticides using spectrophotometric detection providing limits of detection (LODs) at the level of 10 ppb malaoxon equivalents, which is still about 50 times below maximal residue levels. Testing of the method for practical application on a set of 60 samples gave no false negative results and a level of 1.7 % false positives.
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