Quantitation of pesticide residues on thin layer chromatograms by video densitometry

A method is described for analysis of chlorinated pesticides using inexpensive thin-layer plates with quantitation by means of digital image processing. Several organo-halide pesticides, which are classified as priority pollutants, are separated on silica thin-layer chromatographic (TLC) plates using various solvents. The separated pesticide spots are stained with 1% diphenylamine in ethanol, resulting in green- to violet-colored spots. One of the fractions is noticeably different from the other stain/pesticide spots. To take advantage of this color difference, a multiwavelength video TLC scanner is used to determine the reflectance spectrum of each compound in situ. From the digital image resulting from the ratio of two images taken at different wavelengths, the integrated intensity of each pesticide spot is measured and a calibration curve is developed. Detection limits are approximately 1 mu g for each pesticide.<>