Determination of Oxalate in Human Serum in the nM Range by On-Column Sample Preconcentration-Capillary Zone Electrophoresis with Direct Absorbance Detection

For determination of oxalate in serum, capillary zone electrophoresis with direct absorbance detection at 190 nm was combined with the electric field-amplified preconcentration technique. The effects of several variables (the concentration of the background electrolyte, sample dilution factor and sample size) on the sensitivity and resolution of this method were studied. Serum samples were deproteinated by centrifugal filtration through a 5 kD membrane and prior to analysis, diluted 10-fold with water. The limit of detection at S/N=3 was 1.14 nM (0.10 ppb). Linearity was established in the range of 5.68 nM-11.36 μM (0.5 ppb–1.0 ppm) with a correlation coefficient of 0.9999. Recoveries of oxalate from four spiked sera averaged 96.2%. The potential of the method developed was demonstrated by analyzing sera from several healthy adults.