DETERMINATION OF ALPHA-DIALKYLAMINO ACIDS AND THEIR ENANTIOMERS IN GEOLOGICAL SAMPLES BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AFTER DERIVATIZATION WITH A CHIRAL ADDUCT OF O-PHTHALDIALDEHYDE

Derivatization with o-phthaldialdehyde (OPA) and the chiral thiol N-ac etyl-L-cysteine (NAG) is a convenient and sensitive technique for the HPLC detection and resolution of protein amino acid enantiomers. The k inetics of the reaction of OPA-NAC with alpha-dialkylamino acids was i nvestigated. The fluorescence yield of alpha-dialkylamino acids was on ly about 10% of that of protein amino acids when the derivatization wa s carried out at room temperature for 1-2 min, which is the procedure generally used for protein amino acid analyses. The fluorescence yield of alpha-dialkylamino acids can be enhanced by up to ten-fold when th e derivatization reaction time is increased to 15 min at room temperat ure. The OPA-NAC technique was optimized for the detection and enantio meric resolution of alpha-dialkylamino acids in geological samples whi ch contain a large excess of protein amino acids. The estimated detect ion limit for alpha-dialkylamino acids is 1-2 pmol, comparable to that for protein amino acids.