TRACE DETERMINATION OF LOWER VOLATILE FATTY-ACIDS IN SEDIMENTS BY GAS-CHROMATOGRAPHY WITH CHEMICALLY BONDED FFAP COLUMNS

A capillary gas-liquid chromatography method was developed for the quantification of free lower volatile fatty acids (LVFA) in freshwater sediments. The method is based on the application of water-resistant FFAP (free fatty acid phase) columns and splitless injection. An important feature is the ability to determine LVFA directly at picomole levels in 1-3 μl of water without sample extraction, clean-up or derivatization. Continuous saturation of the carrier gas with formic acid is superfluous, making this method compatible with mass-selective detection. Detection limits of 0.2 pmol can be obtained for propionate with mass-selective detection and 1 pmol for acetate with flame ionization detection. The ability to study LVFA metabolism using stable isotope tracers is discussed. The method allows the measurement of well defined concentration profiles (4-70 μM) in sediment pore waters and is a good alternative to existing techniques for determining trace amounts of LVFA in very small volumes of organic-rich matrices. © 1990.