Determination of phenoxy acid herbicides in vegetation, utilising high-resolution gel permeation chromatographic clean-up and methylation with trimethylsilyldiazomethane prior to gas chromatographic analysis with mass-selective detection

A method for the determination of phenoxy acid herbicides in vegetation samples is described. Macerated samples are extracted with acetone and following filtration and acidification, the herbicides are partitioned into dichloromethane. The herbicides are then cleaned-up using high-resolution gel permeation chromatography before undergoing rapid and efficient methylation using trimethylsilyldiazomethane. The resultant methyl esters are then selectively and sensitively analyzed by gas chromatography with mass selective detection. Silanized glassware was used throughout. The method has been applied to grass samples spiked with four phenoxy acid herbicides; 2,4-D, dichlorprop, MCPA and mecoprop. Recoveries around 100% and reproducibilities of 5% (n=4) were achieved at two spiking levels, similar to 700 and similar to 140 mu g/kg.