Determination of dissolved and exchangeable trimethylamine pools in sediments

A highly sensitive method for determination of dissolved and exchangeable trimethylamine (TMA) in sediments is described. The TMA was extracted from pore water samples by addition of base and sparging with inert gas. After a quantitative transfer to cryogenic traps, the gaseous TMA was determined in a gas chromatograph with packed column separation and detection by flame ionization. Column performance was optimal when a spike of ammonium was included in the preparation line. With a duplicate sparging system, the effective analysis time per sample was 15 min. Detection limit was 5 pmol, and distributions of the dissolved and potassium-exchangeable TMA pools in sediments could be determined in microliter volumes of samples (high spatial resolution).