Rapid Spectrophotometric Determination of Organo-phosphorus Pesticides with Plant-hydrolase Catalysis

The hydrolysis of α-naphthyl acetate was catalyzed with plant-esterase,and α-naphthol was obtained.A purple complex was formed by the color reaction of α-naphthol with FeCl3,with its absorption maximum at the wavelength of 516 nm.The color reaction was inhibitated by the presence of organo-phosphorus pesticides,and linear relationship between mass concentration of organo-phosphorus pesticides and decrease of absorbance (ΔA) was obtained.Based on these facts,a method for rapid determination of organo-phosphorus pesticides was proposed.Experimental conditions,including reaction temperature,reaction time,pH of buffer solution and interference of co-existing ions,were studied and optimized.Detection limits (3S/N) of dichlorophos,dipterex,methamidophos,dimethoate and isocarbophos were in the range of 0.001-0.25 mg·L-1,and RSD′s (n=6) found for these pesticides were less than 5.5%.The method was used in the analysis of vegetables,values of recovery found by standard addition method were in the range of 87.0%-93.0%.