Oxidation of organophosphorus pesticides for the sensitive detection by a cholinesterase-based biosensor.
A potentiometric flow injection-type biosensor developed in our laboratory was used for the determination of organophosphorus pesticides (OPs). The principle of the biosensor is that the degree of inhibition of a sensor enzyme by an OP is dependent on the concentration of the pesticide. The sensor system consisted of a reactor with acetylcholinesterase (AChE) immobilized on a controlled pore glass and a detector with a tubular H(+)-selective membrane electrode. In order to examine the possibility of enhancing the sensitivity of the sensor by converting OPs to oxidized forms (stronger inhibitors), a comparison of the degree of enzyme inhibition by OPs at 10(-6) M before and after their oxidation was made. All of the ten pesticides tested exhibited greater inhibitory power toward the sensor enzyme following oxidation. All of the oxidized pesticides at 10(-6) M inhibited the sensor enzyme to a considerable degree, demonstrating the utility of the developed method for the class-specific determination of OPs. A calibration curve for diazinon, over the concentration range of 10(-11)-10(-4) M, was obtained. The lower detection limit was 2 x 10(-10) M. Treatment of the inhibited enzyme with pyridine-2-aldoxime restored the enzyme to near full activity, allowing repeated use of the sensor.
Lee
Hye-Sung
HS
Department of Food Science and Nutrition, Kyungpook National University, Taegu 702-701, South Korea. hslee@knu.ac.kr
Kim
Young Ah
YA
Cho
Young Ae
YA
Lee
Yong Tae
YT
D000110:Acetylcholinesterase / Q000737:chemistry* / Q000187:drug effects; D001681:Biological Assay / Q000379:methods; D002138:Calibration; D004305:Dose-Response Relationship, Drug; D007306:Insecticides / Q000737:chemistry*; D009943:Organophosphorus Compounds; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity
D007306:Insecticides; D009943:Organophosphorus Compounds; D000110:Acetylcholinesterase