Journal of’ Chromatography. 279 (1983) 507-514 Elsevier Science Publishers B.V., Amsterdam ~~ Printed in The Netherlands CHROMSYMP. 067 AMINO ACID DETERMINATION BY CAPILLARY GAS CHROMATOGRA- PHY ON CHIRASIL-VAL ENANTIOMER LABELLING AND NITROGEN-SELECTIVE DETECTION H. FRANK* and N. VUJTOVIC-OCKENGA Imtifut fiir Tosikoiogir, Univrcritiif Tiibingrn, Wilhehmrrasse 56. 7400 Ttihingm (F. R.G.j and A. RETTENMEIER SUMMARY Amino acid analysis by enantiomer labelling and capillary gas chromatogra- phy on Chirasil-Val is superior to conventional gas chromatography and ion-ex- change chromatography with respect to sensitivity, accuracy and speed. Employment of an alkali flame-ionization detector allows the selective detection of amino acids and suppression of background peaks; in addition, the detectability of amino acids is enhanced. Most nitrogen-selective detectors require meticulous adjustment of the operating conditions, but in combination with enantiomer labelling this is less criti- cal. Maximum sensitivity and selectivity of the alkali-bead flame-ionization detector is achieved with a minimal flow of hydrogen. When using it as the carrier gas in capillary gas chromatography, flow control instead of the common pressure regu- lation is recommended to avoid a continuous fall of the baseline during temperature programming. Accurate flow control is achieved with a micro-aperture. The benefit of nitrogen-selective detection is especially apparent for histidine and arginine. INTRODUCTION The determination of amino acids in biological fluids or protein hydrolysates is of great interest in many areas, such as peptide synthesis, protein chemistry, clinical analysis and food chemistry. Amino acid analysis is usually performed by ion-ex- change chromatography, a procedure introduced by Spackman rt al. 25 years ago’. Although gas chromatography was proposed relatively early2s3 as a method poten- tially superior with respect to sensitivity and speed, until recently it suffered from several drawbacks associated with the need for derivatization of amino acids. While sample preparation for ion-exchange chromatography is relatively simple, the pre- treatment for gas chromatography includes additional physical and chemical steps such as sorption of the amino acids on a cation exchanger. desorption with ammonia, 0021-9673j83403.00 c 1983 Elsevier Science Publishers B.V