Measurement of purines in urine by capillary electrophoresis for estimating the degree of hypoxia in infants

We describe a simple, rapid and reproducible method for measuring hypoxanth ine, xanthine and uric acid in urine samples of infants by capillary electr ophoresis with an uncoated fused silica capillary and ultraviolet detection . Conditions were 40 mmol/l berate buffer pH 9.4 with sodium dodecyl sulpha te (0.1 mol) 3s hydrodynamic load and the voltage 20 kV. The calibration cu rves for hypoxanthine and xanthine were linear to 150 mu mol/l and for uric acid to 300 mu mol/l. The limits of detection for hypoxanthine, xanthine a nd uric acid were 0.5, 2.0 and 20 mu mol/l, respectively. Analytical recove ry of the three purines ranged from 93 to 105%. Overall CVs were <5.2%. Usi ng this method, we measured purine concentrations in the urine samples of 1 03 infants, divided into three groups, according to different degrees of hy poxia. There was a significant difference among the three groups only in hy poxanthine concentrations. In 35 urine samples from the control group, 43 u rine samples from infants with a history of an apparent life threatening ep isode and in 25 urine samples from infants with infantile apnoea, the mean concentrations of hypoxanthine (mean +/- SD) were 13.1 +/- 4.0, 25.1 +/- 8. 1 and 58.2 +/- 17.4 mu mol/mmol creatinine, respectively. The diagnostic ac curacy of the purine measurement was evaluated by receiver-operating charac teristic curve analysis.