Determination of D-penicillamine in serum and urine of patients with rheumatoid arthritis.

A chromatographic auto-analyser method is described for the determination of total D-penicillamine in biological fluids. After oxidation with performic acid, D-penicillaminic acid is separated from other ninhydrin-positive acidic amino acids by anion-exchange chromatography. Total cysteine/cystine is simultaneously determined as cysteic acid, which makes the method equally suitable for patients with cystinuria. The detection limit in serum and urine is 2 microM D-penicillamine, which is more than sufficient for clinical application. The metabolite S-methyl-D-penicillamine is oxidized by performic acid to a sulphone, which can be determined after separation by cation-exchange chromatography.