To improve our understanding of both diagnosis and treatment of diseases of oxalate metabolism, we first set out to establish a new ion-chromatographic method to determine normal plasma levels of oxalate, citrate and sulfate from single plasma samples. In 50 infants and children (23 girls, 27 boys, aged 0.2 to 17 years) with normal renal function, blood was drawn in Li-heparin tubes, placed on ice and preserved immediately with 40 microliters M HCl/ml plasma in two ultracentrifugation steps. For measurement, plasma was injected onto an ion chromatography system with NaOH as the mobile phase, and then run as a linear gradient from 5 mM to 52.5 mM over 21 minutes. Analysis yielded measurable and reproducible oxalate (6.43 +/- 1.06 microM/liter), citrate (79.3 +/- 27.4 microM/liter) and sulfate (235.0 +/- 85.3 microM/liter) levels, without any age and gender specific differences. The least detectable plasma oxalate level was < 0.3 microM with a high reliability and reproducibility (coefficient of variance 1.95 to 4.75%). In conclusion, we established a reproducible, precise method to determine the relevant plasma anions involved in mineral metabolism, which heretofore have not been easily measurable. Studies of diseases of oxalate and citrate metabolism are ongoing on the basis of the normal plasma values achieved in this study.
