Direct methylation at the surface of Carbopack B - Part II: Determination of phenoxyalkanoic acid herbicides

The determination of phenoxyalkanoic acids in different types of water with in the limits of the European drinking water guideline is described. Most o f these acids are used world-wide as herbicides and growth regulators. Comp ounds having an acidic hydrogen in their structure are very strongly adsorb ed on Carbopack B, a special graphitized carbon black. This effect was used for the transformation of analytes to methyl esters directly on the surfac e of the adsorbent, using trimethylsulfonium hydroxide (TMSH) as derivatiza tion reagent. After elution with ethyl acetate the derivatives were identif ied and quantified by gas chromatography/mass spectrometry (GC/MS). The int eraction between analyte and adsorbent and the yields of the derivatization step are influenced by the length of the alkanoic chain.