Validation and comparative study of the pesticides detection by enzymatic method

ABSTRACT

Validation and comparison of the detection of malathion and fenitrothion pesticides by the enzymatic method were studied based on cholinesterase inhibition. The equation of non-competitive inhibition was used to calculate the inhibitor concentration and the inhibition rate constant. Linear relationships were obtained for malathion and fenitrothion indicating that the enzymatic assay of pesticides could be represented by the kinetic equation of the non-competitive inhibition. The inhibition constant K_I was 0.297 mg/ml/min for fenitrothion and 1.587 mg/ml/min for malathion. The concentrations of malathion and fenitrothion pesticides inhibited the enzyme by 50% (IC50) were 0.2 mg/ml and 0.35 mg/ml, respectively. The analytical logarithmic curve for the determination of the concentrations of pesticides using the percentage inhibition of cholinesterase enzyme presented good linear relation at concentrations range within the same range of non-competitive inhibition equation. The enzymatic assay exhibited detection limits (LOD) and linearity in the ranges 0.025–2.5 mg/ml for fenitrothion and 0.03–20 mg/ml for malathion. The precision study was performed using tomato extracts. Coefficients of variation ranging from 1.27% to 7.22% were obtained which indicate a good precision of the assay. The extraction method by acetone is effective for determining fenitrothion in tomato matrix.

KEYWORDS:

• Kinetic
• enzymatic method
• organophosphate
• cholinesterase inhibition

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Disclosure statement

No potential conflict of interest was reported by the author.