Fluorimetric determination of amino acids by high-performance liquid chromatography using a hollow-fibre membrane...

A high-performance liquid chromatographic method has been developed for the determination of primary amino acids. The method involves separation of primary amino acids on a C18 column using sodium heptanesulphonate as an ion-pairing agent, post-column derivatization with o-phthalaldehyde and 2-mercaptoethanol introduced into the main flow stream using a sulphonated hollow-fibre membrane reactor immersed in their solutions and fluorimetric detection of derivatives (lambda ex = 340 nm, lambda em = 450 nm). A higher or similar sensitivity was obtained compared with the conventional post-column derivatization method. The detection limits were 0.2-2.3 pmol at a signal-to-noise ratio of 3. For amounts of 48-110 pmol, the precision was of the order of 1.1-4.0% (relative standard deviation, n = 20).