Amino acid determination by capillary gas chromatography on Chirasil-Val. Enantiomer labelling and nitrogen-selective detection.

Amino acid analysis by enantiomer labelling and capillary gas chromatography on Chirasil-Val is superior to conventional gas chromatography and ion-exchange 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 critical. 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 regulation 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.