Determination of organophosphorus pesticide residues in vegetables by an enzyme inhibition method using α-naphthyl acetate esterase extracted from wheat flour |
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| Authors: | Jun-liang Wang Qing Xia An-ping Zhang Xiao-yan Hu and Chun-mian Lin |
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| Institution: | 1International Joint Research Center for Persistent Toxic Substances, College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310014, China;2Zhejiang Province Environmental Radiation Monitoring Center, Hangzhou 310012, China |
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| Abstract: | The widespread use of organophosphorus pesticides (OPs) poses a great threat to human health and has made the detection of
OP residues in food an important task, especially in view of the fact that easy and rapid detection methods are needed. Because
OPs have inhibitory effects on the activity of α-naphthyl acetate esterase (ANAE) in plants, in this work we evaluated the
possibility of detecting OPs in vegetables with ANAE extracted from commercial flour. The limits of detection (LODs) obtained
for methamidophos, dichlorvos, phoxim, dimethoate, and malathion in lettuce samples with crude ANAE were 0.17, 0.11, 0.11,
0.96, and 1.70 mg/kg, respectively. Based on the maximum residue limits (MRLs) for OPs in food stipulated by Chinese laws
which are 0.05, 0.20, 0.05, 1.00, and 8.00 mg/kg for methamidophos, dichlorvos, phoxim, dimethoate, and malathion, respectively,
the esterase inhibition method with crude ANAE had sufficient sensitivity to detect the residues of dichlorvos, dimethoate,
and malathion in lettuce, but it could not be used to guarantee the safety of the same samples if methamidophos or phoxim
residue was present. The sensitivity of the method was improved by the use of esterase purified by ammonium sulfate salting-out.
The LODs obtained for methamidophos and phoxim with purified esterase were lower than the MRLs for these OPs in food. This
is a very promising method for the detection of OP residues in vegetables using crude or purified esterase because of its
cheapness, sensitivity, and convenience. |
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| Keywords: | Organophosphorus pesticides (OPs) α-Naphthyl acetate esterase (ANAE) Limit of detection (LOD) Enzyme inhibition Maximum residue levels (MRLs) |
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