Development of a rapid method for the quantification of methamidophos and chlorpyrifos by Thin Layer Chromatography in soils using image processing

Abstract

The objective of this research was to develop a rapid method to identify and quantify chlorpyrifos and methamidophos in soils by Thin Layer Chromatography. A mobile phase of chloroform:acetone (80:20) was used for methamidophos and for chlorpyrifos a mixture of chloroform: cyclohexane (60:40) was used as mobile phase. The developer consisted of a 0.12 M ethanolic solution of silver nitrate. The stains were processed using "Image J" software. The results show retention factors "Rf" of 0.19 and 0.82 for methamidophos and chlorpyrifos respectively. Both methods for the determination of chlorpyrifos and methamidophos are linear with coefficients of determination R 2 greater than 0.99, precise with RSD less than 15 % and accurate with %R close to 100 %. The analysis of agricultural soil samples of Garlic and Onion showed the presence of chlorpyrifos with concentrations of 0.067 and 0.047 mg/kg respectively. Also, methamidophos was found in alfalfa agricultural soils with a concentration of 0.011 mg/kg. With the results found, it is demonstrated that image processing with "Image J" for the analysis of stains on silica gel plates developed with silver nitrate in the analysis of organophosphates can be taken into account for demonstrative studies for educational purposes and routine tests in toxicology and environment.