INCREASED PARAOXON DETECTION WITH SOLVENTS USING ACETYLCHOLINESTERASEINACTIVATION MEASURED WITH A CHOLINE OXIDASE BIOSENSOR

Inactivation by paraoxon of free and immobilized acetylcholinesterase, in the presence of various amounts of different organic solvents, and with choline oxidase immobilized on an oxygen electrode was studied. With acetylcholinesterase in solution it was found that 5% cyclohexane enhances paraoxon detection when compared to the detection without so lvent. In these conditions, as low as 10(-9) M paraoxon can be detecte d. Free acetylcholinesterase was more sensitive to paraoxon than immob ilized acetylcholinesterase, depending on the nature and concentration of solvent (500-fold in the presence of 5% cyclohexane). The stabilit y of the biosensor in continuous use and stored at room temperature wa s at least 3-4 weeks with triton X100 and bovine serum albumin additio n. The sensitivity of paraoxon detection with free acetylcholinesteras e in the presence of 5% cyclohexane corresponds to 0.2 ppb paraoxon, 1 0-fold below the legal limit admitted in the European Economic Communi ty. The same approach could be applied for detection of low amounts of different organophosphorus or carbamate pesticides. (C) 1996 Elsevier Science Limited