FLOW-INJECTION STUDY OF INHIBITION AND REACTIVATION OF IMMOBILIZED ACETYLCHOLINESTERASE - DETERMINATION OF THE PESTICIDES PARAOXON AND CARBAMOYLCHOLINE

The inhibitory effects of paraxon and carbamoylcholine as examples of organophosphorus and carbamate pesticides, respectively, on the activi ty of acetylcholinesterase (AChE) immobilized on controlled pore glass have been investigated, using a dual injection flow system and spectr ophotometric detection. Reactivation of the inhibited immobilized AChE by pyridine-2-aldoxime methochloride (2-PAM), magnesium or fluoride i ons has also been studied. 2 x 10(-5) M 2-PAM restores almost 100% of the activity of the immobilized enzyme. Methods for determination of p araoxon and carbamoylcholine are presented, based on the inhibition an d reactivation of immobilized AChE as monitored by its catalyzed hydro lysis of acetylthiocholine iodide and the subsequent reaction of the t hiocholine produced with 5,5'-dithiobis(2-nitrobenzoic acid). The cali bration graphs are linear up to 8 x 10(-4) M and 6 x 10(-4) M, respect ively, with relative standard deviations (n = 5) of 5%, and 3sigma lim its of detection of 5 x 10(-5) M and 6 x 10(-5) M, respectively.