Determination of Low Molecular Weight Volatile Fatty Acids in Aqueous Samples

An Ion-exchange/derivatization procedure is described for the determination of C_1-C_5 volatile fatty acids in a range of difficult aqueous matrices. The resulting p-bromophenacyl esters may be separated via either HPLC or GLC techniques depending on desired selectivity and sensitivity. Micromolar concentrations of these acids can be determined to better than ±0.20 μM within 95% confidence intervals. Sewage and marine sediment pore water analyses can be performed on small samples (<25 ml). Similarly, nanomolar determinations are possible in 1-4 L rainwater samples. The analytical method is rapid, economical, and lends itself to routine applications involving parallel determinations of other soluble compounds.