DETERMINATION OF D-AMINO-ACIDS AND L-AMINO-ACIDS IN BIOLOGICAL SAMPLES BY 2-DIMENSIONAL COLUMN LIQUID-CHROMATOGRAPHY

A two-dimensional, column liquid chromatographic system is used for th e determination of the D- and L-enantiomers of amino acids in biologic al samples. Separation of the amino acids is first on ion-exchange col umn by gradient elution with a sodium citrate-sodium chloride buffer. Enantioseparation is by subsequent injection of 3 mu l heart-cuts of t he individual amino acids onto a second column with a chiral crown eth er stationary phase. Finally, fluorescence detection is after post-col umn labelling of the amino acids using an o-phthalaldehyde-2-mercaptoe thanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additio nal treatment and the determination of small quantities of D-amino aci ds in the presence of excess L-form. Applicability of the system is il lustrated by the determination of D- and L-aspartate, serine, glutamat e and alanine in various complex biological samples, such as protein h ydrolysates, urine and biotechnological and food samples. Data are giv en on detectability, repeatability and linearity.