SPECTROPHOTOMETRIC METHOD TO DETERMINE TERNARY MIXTURES OF ATRAZINE, DIURON, AND CHLORPYRIFOS IN WATER AND SOIL BY A RATIO SPECTRUM ZERO-CROSSING METHOD

A spectrophotometric method based on simultaneous use of first derivat ive of ratio spectra and measurement of zero-crossing wavelengths reso lves ternary mixtures of atrazine, diuron, and chlorpyrifos. Calibrati on graphs were linear for atrazine between 1 and 15 mu g/mL and for di uron and chlorpyrifos between 1 and 10 mu g/mL. The pesticides in grou ndwater and soil were determined by the method, at part-per-billion le vels, after solid-phase extraction, with good results. Interferences c aused by other pesticides were studied.