Analysis of nitrite and nitrate in biological fluids by capillary electrophoresis

Objectives: We report a method for determining nitrite and nitrate in biolo gical fluids by capillary electrophoresis. Methods: A Waters capillary electrophoresis system was used with a filter f or detection at 214 nm. After dilution with distilled water, the sample was loaded hydrostatically onto a 60 cm x 100 mu m capillary and electrophores ed at 15 kV in 15 mmol/L sulfate buffer, pH 8.0, containing 2.5% electroosm otic 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 mu mol/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 mu mol/L) and high (8 7 mu mol/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 p articularly suitable for clinical laboratories. Copyright (C) 1999 The Cana dian Society of Clinical Chemists.