Determination of chlorpyrifos and diazinon insecticides using derivatives absorption spectrophotometric method.

Chlorpyrifos and diazinon are insecticides used commonly to control oriental fruit moth, codling moth, apple maggot, and mites in a range of situations. It is used widely to control insects of agricultural and public health significance. A method was developed for determination of chlorpyrifos and diazinon based on derivative absorption spectrometry. Fenvalerate and triflumuron are insecticides that are some times used with chlorpyrifos and diazinon. They have a large effect on the determination of chlorpyrifos and diazinon due to the overlapped spectra. Therefore, derivative absorption spectrometry was developed for determination of chlorpyrifos and diazinon in the presence of fenvalerate and triflumuron in order to overcome this problem. Second derivative (D2) at 308 nm and third derivative (D3) at 304 nm were used to measure the chlorpyrifos in the presence of fenvalerate, and diazinon and triflumuron, respectively. The D2 and D3 spectra have a linear range of (1-150) ppm, with correlation coefficient 0.9999. The slope of the linear calibration curve of the D2 and D3 were 0.0255 and 0.0012, respectively. D2 at 305 nm and D3 at 300 nm were also used to measure the diazinon in the presence of fenvalerate and triflumuron, respectively. The calibration curves for the D2 and D3 spectra have a linear range of (5-200) ppm and (10-150) ppm, with correlation coefficient 0.9991 and 0.9994,
respectively. The slope of the linear calibration curve of the D2 and D3 were 0.0006 and 0.0004, respectively. The standard addition method was also used to measure the active ingredient in the commercial available insecticides of chlorpyrifos and diazinon. It is found that the standard addition curve of the D2 and D3 spectra give the true value of the active ingredient as listed on the label of the commercial insecticide.