Due to medical relevance and a direct correlation with some diseases, accurate quantification of oxalic acid in different complex matrices is required. Effective chromatographic separation of this strong carboxylic acid was achieved by ion exclusion chromatography (IELC). Sensitive and selective detection was carried out by means of electrospray ionization-tandem mass spectrometry. Furthermore, it was shown that the isobaric interference of lactic acid is chromatographically resolved. Structurally similar compounds like glyoxylic acid and glycolic acid were baseline separated as well. The application of stable isotope dilution analysis with 13C2 oxalic acid facilitated precise quantification. The developed method was validated with a reference oxalate sample of human urine diluted to a range of 10-500μM. Finally, the applicability of this method was demonstrated on complex matrices, like mouse urine and supernatants of primary mouse hepatocyte cell cultures.
Keywords: Ion exclusion chromatography; MS/MS; Oxalic acid quantification; Stable isotope dilution analysis.
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