Disposable biosensor test for organophosphate and carbamate insecticides in milk

摘要

A highly sensitive and rapid biosensor test based on disposable screen-printed thick-film electrodes was developed, which is suitable for monitoring organophosphate and carbamate residues in foods of animal origin with increased fat contents such as milk. The wild-type enzyme was combined with three engineered variants of Nippostrongylus brasiliensis acetylcholineste rase (NbAChE), to obtain enhanced sensitivity. The sample pretreatment could be reduced to a minimum. There was no extraction or fat removal necessary. With the biosensor test paraoxon concentrations down to 1 mu g/L could be detected in milk. The detection limit for carbaryl was 20 mu g/L. Recovery rates for paraoxon and carbaryl in milk samples lay between 89 and 107%. Ten milk samples from local markets were tested both with the biosensor test and with standard chromatographic multiresidue methods. Two milk samples caused AChE inhibition rates of > 50%. Accordingly, 4 mu g/L tebufenpyrad, 4 mu g/L tetraconazole, and 2 mu g/L bifenthrin were detected in one of these milk samples. The other milk sample contained 2 mu g/L tebufenpyrad.