[Quantitative measurement of oxalic acid in urine by liquid chromatography combined with tandem mass spectrometry].

To find a suitable method for the determination of oxalic acid in the urine of patients with stones, in order to provide a new method and basis for the prevention and treatment of stone. Liquid chromatography combined with tandem mass spectrometry was used to analyze oxalic acid in urine directly.The accuracy, stability, repeatability and other indicators of the results were tested. The results showed a good linear relationship with the concentration of oxalic acid in urine. y=58.524x-15.246 (R(2)=0.979 02). The results were stable, reproducible (the intra-day and inter-day coefficient of variation was less than 10% and 15%, respectively), and the accuracy was comparable with that of the enzyme method (N=20, R=0.93). Using the method of this study to detect the content of oxalic acid in urine has the advantages of simple operation, good repeatability, accurate results, and low price. It is worth to be popularized and applied in clinical practice.