Electron capture gas-liquid chromatographic method for the simultaneous analysis of 2,4-D, dicamba, and mecoprop residues in soil, wheat, and barley.

A method has been developed for the simultaneous analysis of 2,4-D (2,4-dichlorophenoxy-acetic acid), dicamba (2-methoxy-3,6-dichloro-benzoic acid), and mecoprop (MCPP; 2-[(4-chloro-o-tolyl) oxy] propionic acid) residues in soil, wheat, and barley. Soil and crop samples are extracted with acidic acetone and methanol, respectively. The extracts in diethyl ether are esterified with diazomethane and cleaned up by passing through a Florisil column. Extracts are analyzed by gas-liquid chromatography, using an electron capture detector to determine 2,4-D and dicamba residues. Mecoprop in the extract is not detected at low levels of concentration. However, bromination of the extract increases the response of the electron capture detector to mecoprop. The method is sensitive to about 0.05 ppm 2,4-D and dicamba and 0.5 ppm mecoprop. Recoveries of these 3 herbicides added to soil, wheat, and barley samples at 0.05, 0.1, 0.5, and 1.0 ppm levels were between 65 and 93%. The method was used for the simultaneous analysis of 2,4-D, dicamba, and mecoprop residues in wheat, barley, and soil samples obtained from fields sprayed with the herbicide formulation Kil-Mor.