The use of an acetylcholinesterase inhibition assay for the detection of dichlorvos in durum wheat samples by a simplified extraction procedure is reported. After an incubation step, the residual activity was determined with an amperometric biosensor using a portable potentiostat. The
use of electric eel and recombinant acetylcholinesterase was compared. The effect of the matrix extract was evaluated by using various sample:solvent ratios, 1:2.5, 1:5, 1:10, and 1:20. The optimal extraction ratio, considering the electrochemical interferences and the effect on enzyme activity
and bioavailability of the pesticide, was 1:10. Calibrations were performed in buffer and durum wheat extract. The calculated detection limits in buffer solution were 10 ng/ml and 0.045 ng/ml for electric eel and recombinant acetylcholinesterase, respectively, whereas operating in the matrix
extract they increased up to 45 ng/ml and 0.07 ng/ml, corresponding to 0.45 mg/kg (extraction ratio 1:10) and 0.07 mg/kg in samples. These characteristics allowed the detection of contaminated samples at the maximum residue limit, which is 2 mg/kg and well below. Fortified samples of durum
wheat were obtained with both dichlorvos and the commercial product Didivane, which contains dichlorvos as an active molecule. At all the tested levels, the occurrence of contaminant was detected with an average recovery of 75%. The total assay time, including the extraction step, was 30 min.
Because several extractions as well as most of the assay steps can be run simultaneously, the throughput for one operator is 12 determinations per hour.
Document Type: Research Article
Department of Food Science, University of Teramo, 64023 Teramo, Italy 2:
Centre de Phytopharmacie, Université de Perpignan, 66860, Perpignan, France 3:
Laboratoire de Synthèse et Phytochimie des Molécules d'Intérèt Biologique, Université Paul Sabatier, Tolouse, France 4:
Institute of Sciences of Food Production ISPA-CNR, 70126 Bari, Italy
Publication date: June 1, 2006
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