Sensitive detection of pesticides using amperometric sensors based on cobalt phthalocyanine-modified composite electrodes and immobilized cholinesterases.
The determination of organophosphate and carbamate pesticides was carried out using cobalt phthalocyanine-modified carbon epoxy composite electrodes coupled with acetylcholinesterase or butyrylcholinesterase. Covalent immobilization of enzymes on Immobilon membranes or nylon nets was examined; the highest sensitivity to inhibitors was found for the nylon net containing low enzyme loading and this was subsequently used for the construction of an amperometric biosensor for pesticides. Analyses were done using acetyl- or butyrylthiocholine as substrates; thiocholine produced by hydrolysis in the enzyme membrane was electrochemically oxidized at +300 mV (vs. Ag/AgCl reference). The decrease of substrate steady-state current caused by the addition of pesticide was used for evaluation. With this approach, 1.5 and 8.4 micrograms l-1 of paraoxon and heptenophos, respectively, can be detected in less than 3 min. These detection limits are similar as those obtained when analyses were performed using free cholinesterase and 10 min incubation with inhibitor.
Skladal
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Dipartimento di Sanita Pubblica, Epidemiologia e Chimica Analitica Ambientale, Sezione di Chimica Analitica, Florence, Italy.
Mascini
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D015374:Biosensing Techniques; D002219:Carbamates; D002802:Cholinesterases / Q000737:chemistry*; D003035:Cobalt; D004553:Electric Conductivity; D004800:Enzymes, Immobilized; D007211:Indoles / Q000737:chemistry*; D007306:Insecticides / Q000032:analysis*; D009942:Organometallic Compounds / Q000737:chemistry*; D009943:Organophosphorus Compounds; D012680:Sensitivity and Specificity; D012995:Solubility; D013997:Time Factors
D002219:Carbamates; D004800:Enzymes, Immobilized; D007211:Indoles; D007306:Insecticides; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; C063633:cobalt phthalocyanine; D003035:Cobalt; D002802:Cholinesterases