An electron-capture gas chromatographic procedure for the estimation of oxalic acid in urine

✍ Scribed by D.J. Tocco; A.E.W. Duncan; R.M. Noll; D.E. Duggan

• Publisher: Elsevier Science
• Year: 1979
• Tongue: English
• Weight: 417 KB
• Volume: 94
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(79)90390-7

✦ Synopsis

An analytical procedure for the estimation of urinary oxalate is described which satisfies the requirements of specificity, recovery, and negligibIe generation of oxalate from progenitors. The procedure involves precipitation of oxalate from urine as the calcium salt and subsequent diesterification with 2chloroethanol.

The derivative is detected by electron capture-gas chromatography with [Wloxalate used as a recovery standard. The electron-capture response is linear over the range of 5 to 40 pg carried through the procedure. The coefficient of variation in replicate aliquots over the entire range is 7%. Total urinary oxalate excretion for the periods 0800-1200, 1200-1600, and 1600-0800 h on the following day were determined for each of eight volunteers over periods of 5 or 7 days. The mean excretion of oxalate was 35.6 2 11.9 mg/day. There was no suggestion of a diurnal pattern in oxalate excretion. Oxalate levels in dog plasma, as determined by the electron capture-gas chromatographic procedure, were high (-0.7 &ml) compared to theoretical oxalate levels (0.1 to 0.2 &ml) as estimated from the renal clearance of [lsC]oxalate or [Yloxalate.

These data clearly indicate that oxalogenesis occurs during the assay of plasma, even under the mildest of separation conditions.