| Abstrakt: |
An enzymatic inhibition method sufficiently sensitive for rapid screening of seven organophosphorus pesticides in water is described. Azinophos methyl, chlorpyriphos, diazinon, fenthion, methamidophos, methidathion, and omethoate were enriched from water samples by solid-phase extraction (SPE) on SDB-1 and C18cartridges. Recovery rates were between 94 and 102% for both extraction materials except for chlorpyriphos on C18; relative standard deviations were ±0.7–3.7% and 1.1–4.9% for SDB-1 and C18cartridges, respectively. The pesticides were separated on silica gel TLC plates with n-hexane—acetone, 75 + 30 (v/v) as mobile phase. Calibration plots were linear between 100 and 2000 ng for all pesticides; correlation coefficients, r, were between 0.9994 and 0.9997. An enzymatic analysis technique on TLC plates was developed using 7-diethylamino-3-(4’-maleimidylphenyl)-4-methylcoumarin (maleimide CPM) as fluorogenic reagent. It reacts with thiocholine released after hydrolysis of acetylthiocholine with acetylcholinesterase at pH~8 to form a strongly blue fluorescent background. In this way, the sites of enzyme inhibition by organophosphorus pesticides can be identified as dark spots. The limit of detection was between 1 and 10 ng spot−1. |
Full text from SpringerLink