Liquid Chromatographic Determination of Amino Acids After Precolumn Fluorescence Derivatization

Certain amino acids are now well established as the transmitters employed by the majority of neurons in the central nervous system (Curtis and Johnston, 1974; Watkins and Evans, 1981; Fagg and Foster, 1983). Investigation of the physiology, pharmacology, and biochemistry of these amino acids in relation to neurotransmission demands their quantification at low concentrations in both tissue extracts and extracellular fluids of the brain. Amino acids in physiological fluids are conventionally determined by ion-exchange chromatography and postcolumn derivatization (Stein and Moore, 1954 ). The resolution is well characterized and the technique is sensitive when fluorogenic reagents are used. However, an analysis time up to several hours is generally required for separation of amino acids Over the last 10 yr, liquid chromatography, previously named high-performance liquid chromatography (Ettre, 1981 ), has experienced explosive growth. The use of precolumn fluorogenic derivatization in combination with reversed phase liquid chromatography has simplified and improved the separation of amino acids. This system today constitutes an attractive alternative to the conventional amino acid analyzers (Lindroth and Mopper, 1979 ; Ejnarsson et al., 1983 ).