HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF SUBPICOMOLE AMOUNTS OF AMINO-ACIDS BY PRECOLUMN FLUORESCENCE DERIVATIZATION WITH ORTHO-PHTHALDIALDEHYDE

Using reversed-phase high performance liquid chromatography, 25 amino acids as o-phthaldialdehyde derivatives were determined with a 30-min sample turnover. The derivatization procedure is rapid, performed in aqueous medium, and has few transfer steps. The precision is ±0.5% at the 80-pmol level. Recoveries of standards added to urine samples were >98%. Intercalation with an amino acid analyzer showed an agreement of >95 %. The detection limit Is about 50 fmol. The overall retention is controlled by the organic modifier, but second-order effects are ascribed to Ion repulsion between anions in the eluent and the ionized carboxylate on the derivatives. Clinical, biochemical, and environmental applications are given. Amino acids and ammonia were determined In 25 μL of seawater. © 1979, American Chemical Society. All rights reserved.