Measurement of urinary amino acids using high-performance liquid chromatography equipped with a strong cation exchange resin pre-column

We determined the urinary amino acid concentrations by highperformance liqu id chromatography (HPLC) using an eluent buffer which had been processed th rough a column packed with strong cation-exchange resin. With this column, ghost peaks resolved or much reduced in size and shifted to a post-arginine position. A clearer separation of peaks of urinary amino acids and ammonia was obtained. This could be due to the elimination of O-phthalaldehyde rea ctive substances in the eluent by the resin column. This method does not re quire a separate step to remove ammonia, unlike most of the methods current ly used, and thus saves time.