Analysis of nitrite and nitrate in biological fluids by capillary electrophoresis

Abstract

Objectives: We report a method for determining nitrite and nitrate in biological fluids by capillary electrophoresis. Methods: A Waters capillary electrophoresis system was used with a filter for detection at 214 nm. After dilution with distilled water, the sample was loaded hydrostatically onto a 60 cm × 100 μm capillary and electrophoresed at 15 kV in 15 mmol/L sulfate buffer, pH 8.0, containing 2.5% electroosmotic flow modifier. Results: The retention times for nitrite and nitrate were 3.9 ± 0.8 and 4.0 ± 0.8 min, respectively. The detection limit was 10 μmol/L for serum nitrate.The recovery was 93–115% for nitrite and 92–106% for nitrate. The within-day and between-day coefficients of variation were lower than 3.3% and 5.0%, respectively, for two pools with normal (28 μmol/L) and high (87 μmol/L) nitrate concentration. A comparison with the nitrate reductase method gave a correlation coefficient of 0.982. Conclusion: Capillary electrophoresis provides many advantages, namely low cost, small sample and buffer requirements, rapidity, which makes its use particularly suitable for clinical laboratories.