Spectrophotometric Determination of Carbaryl Residues in Vegetables Using Crude Peroxidase from Wheat Bran

A.M Magomya and A.M Ago

Abstract

A spectrophotometric method for the determination of carbaryl based on the catalytic reaction of peroxidase enzyme is presented. The method involves the alkaline hydrolysis of carbaryl into 1-naphthol followed by enzymatic reaction with peroxidase in the presence of 4- aminoantipyrine and hydrogen peroxide to yield a red-coloured product which is measured at 502 nm. Wheat bran was exploited as a source of peroxidase in this study and the enzyme was extracted by a simple method without any purification. Parameters influencing the enzyme assay activity such as concentrations of NaOH, hydrogen peroxide, 4-aminoantipyrine, pH and incubation time were investigated and optimized. Under optimized conditions, absorbance of the system was found to be proportional to carbaryl concentration in the range of 0.5– 2.5 mg L ?1 with R 2 value of 0.987. Limit of detection (LOD) and limit of quantitation (LOQ) for the system were 0.22 mg L ?1 and 0.67 mg L ?1 respectively. Application of the method to the determination of carbaryl residues in spiked vegetable samples revealed good recoveries ranging from 86 - 118 %. Relative standard deviation (RSD) for intraday measurements (n=7) were 4.25 % and 2.72 % for 0.5 and 1 mg/L concentration respectively. Overall, the investigated method showed good sensitivity and selectivity for the quantitative analysis of residual carbaryl.

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