Isolation of chlorophenoxy herbicides on columns of glass beads.

A method for the analysis of chlorophenoxy herbicide residues has been developed based on the observed adsorptive affinity of chlorophenoxy acids for glass surfaces. Extracted residues of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) herbicides are adsorbed onto a column of fine mesh glass beads, and subsequently esterified with diazomethane for gas-liquid chromatographic quantitation, using an electron capture detector. Prior to injection, the esterified sample is cleaned up by passing through a Florisil column. The method is sensitive to about 0.5 ppm 2,4-D and 0.01 ppm 2,4,5-T. Recoveries averaged from 81 to 101%, depending on the level added and the substrate.