The determination of oxalic acid in plasma and urine by means of capillary gas chromatography.

A gas chromatographic procedure for determining oxalate in plasma is described, in which the trimethylsilyl derivative of oxalate is analyzed on a 25-m capillary SE-30 column. In addition the effects of standing of whole blood or plasma and the effect of added glyoxalate on the oxalate concentration were studied. The present method offers good specificity and sensitivity and is easy to perform, in contrast to most methods hitherto described. The normal value of plasma oxalate was found to be 2.8 +/- 1.1 mumol/l (mean +/- 1 SD), which is close to the values obtained with in vivo tracer studies. Plasma oxalate values before and after haemodialysis are presented. By introducing a few minor modifications the method is also applicable to urine samples and in principle it should be possible to determine the glycollic acid concentration as well, both in urine and plasma.