Trace spectrophotometric determination of dichlorvos using diphenyl semicarbazide (DPC) in environmental and agricultural samples

A new and highly sensitive spectrophotometric method is developed for the determination of sub ppm levels of the widely used organophosphorus insecticide dichlorvos. The method is based on alkaline hydrolysis of dichlorvos to dichloroacetaldehyde followed by coupling with diphenyl semicarbazide (DPC) in alkaline medium. The absorption maxima of the wine red dye compound formed is measured at 490 nm. Beer's law is obeyed over the concentration range of 4.3 to 34 mu g in a final solution volume of 25 mL (0.18-1.36 ppm). The molar absorptivity, Sandell's sensitivity and correlation coefficient were found to be 2.9 x 10(5) l mole(-1)cm(-1), 0.013 mu g cm(-2) and 0.9999, respectively. The standard deviation and relative standard deviation were found to be +/- 0.007 and 1.90%, respectively. The lower limit of detection is 0.04 mu g. The method is simple, sensitive and free from interferences of other pesticides and diverse ions. Other organophosphorous pesticides do not interfere with the proposed method. The method has been satisfactorily applied to the determination of dichlorvos in environmental and agricultural samples.