Isotachophoretic determination of short-chain fatty acids in drinking water after solid-phase extraction with a...

A macroporous carbon sorbent, packed into disposable columns (Separcol-Carb), was investigated for the off-line preconcentration of short-chain fatty acids from drinking water in conjunction with their determination by capillary isotachophoresis (ITP). Of the acids investigated (C1-C9), butyric acid and higher homologues could be enriched into a high degree from samples of drinking water. Their detection limits from the ITP conductivity detector were in the low parts per 10(9) range when an amount equivalent to 8 ml of the sample was taken for analysis. The lowest homologues (C1-C3) were not adsorbed sufficiently to achieve their reasonable enrichment by the sorbent under the working conditions employed (acidification of the sample to pH 2.0). Acetone and diethyl ether were employed for the elution of the adsorbed analytes. The latter was more convenient in the analysis of practical samples as it co-eluted a considerably smaller number of the adsorbed anionic constituents. Octadecyl-bonded silica, evaluated in parallel, was found to be of only very limited utility for the same purpose.