Liquid chromatographic determination of methylamines. Determination of trimethylamine in fish samples using a porous graphitic carbon stationary phase

A method is described for the separation of methylamine, dimethylamine and trimethylamine on porous graphitic carbon (PGC) using ion interaction chromatography. The method developed used an aqueous eluent of 5 mM heptane sulphonic acid in 5 mM sodium phosphate buffer at pH 9. Calibration graphs were linear in the range 0.1–10 mM for trimethylamine and 5–50 mM for methylamine and dimethylamine; the relative standard deviation for each amines was 3.1%. The method was applied to the determination of trimethylamine in fish tissue and recoveries of 99.7–102.0% were obtained for the fish extracts. The levels of trimethylamine in freshly defrosted cod were below the detection level of the method, but 2.2 mM was found in extracts of samples stored for 14 days at 4°C.