MEASUREMENT OF ASCORBIC-ACID IN HUMAN PLASMA AND URINE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY RESULTS IN HEALTHY-SUBJECTS AND PATIENTS WITH IDIOPATHIC CALCIUM UROLITHIASIS

A simple, reliable high-performance liquid chromatographic method was developed to measure ascorbic acid (ASC), with ultraviolet detection ( 250 nm), in human plasma and urine. Immediately following blood withdr awal, the heparinized plasma samples were deproteinized with 10% m-pho sphoric acid, while the freshly voided urine samples were diluted with m-phosphoric acid. ASC was separated on a reversed-phase column by el ution with 0.1 M KH2PO4 adjusted to pH 2.35. In urine, after reduction of dehydroascorbic acid to ASC, total ASC was measured using the same mobile phase. The method was sensitive down to 0.1 and 0.4 mg ASC per litre of urine and plasma, respectively. In patients with idiopathic calcium urolithiasis, both plasma and urinary ASC were within the rang e observed in age-matched controls.