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Simultaneous determination of oxalate, citrate and sulfate in children's plasma with ion chromatography
B Hoppe1, M J Kemper, M G Hvizd
1Division of Pediatric Nephrology, Northwestern University, Children's Memorial Hospital, Chicago, Illinois, USA.
Insights
A new ion-chromatographic method accurately measures plasma oxalate, citrate, and sulfate levels. This breakthrough aids in understanding and treating diseases of oxalate metabolism.
Area of Science:
- Clinical Chemistry
- Analytical Chemistry
- Pediatric Nephrology
Background:
- Diseases of oxalate metabolism require accurate diagnostic and therapeutic tools.
- Existing methods for measuring plasma oxalate, citrate, and sulfate are often insufficient.
Purpose of the Study:
- To develop and validate a novel ion-chromatographic method for simultaneous determination of plasma oxalate, citrate, and sulfate.
- To establish reference ranges for these analytes in a pediatric population.
Main Methods:
- Developed an ion chromatography method using NaOH as the mobile phase with a linear gradient.
- Analyzed plasma samples from 50 healthy infants and children (aged 0.2–17 years).
- Employed ultracentrifugation for plasma sample preparation and preservation with HCl.
Main Results:
- Established reproducible and precise measurements for plasma oxalate (6.43 ± 1.06 µM/L), citrate (79.3 ± 27.4 µM/L), and sulfate (235.0 ± 85.3 µM/L).
- Determined a lower limit of detection for plasma oxalate below 0.3 µM with high reliability (CV 1.95–4.75%).
- Found no significant age or gender-specific differences in plasma levels of these analytes.
Conclusions:
- Successfully established a reproducible and precise ion-chromatographic method for measuring key plasma anions.
- The method facilitates the study of mineral metabolism and diseases related to oxalate and citrate.
- This work provides essential normal plasma values for future clinical and research applications.
Abstract:
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.