CHROMATOGRAPHY OF 99 AMINO-ACIDS AND OTHER NINHYDRIN-REACTIVE COMPOUNDS IN THE PICKERING LITHIUM GRADIENT SYSTEM

High-performance liquid chromatographic systems can be adapted to the high-resolution determination of free amino acids with hardware and reagents from Pickering Labs. The lithium-based eluent gradients used allow good separations to be achieved isothermally in 2 h. Although the overall elution pattern correlates strongly with those of established automated methods, the differences can be large, and are numerous enough that one type of system cannot serve as a predictor for the other. Relative retention times in the Pickering system were determined for 99 ninhydrin-positive compounds: imino acids, ureides, amino sugars, amino acids and derivatives, with emphasis on those occurring in plants.