The determination of nitrite and nitrate in human blood plasma by capillary zone electrophoresis

The determination of nitrite and nitrate in human blood plasma by capillary zone electrophoresis (CZE) is described. Electrophoresis was carried out in a 65 cm long, 75 microns wide silica capillary, using 750 mM sodium chloride containing 5% NICE-Pak OFM Anion-BT (an additive reversing the electroosmotic flow) as running buffer, at a potential of 20 kV, with on-column UV detection at 214 nm. Under these conditions, the two anions migrated in the order of nitrite and nitrate, completely resolved from each other. Forty-one samples of ultrafiltered blood plasma of healthy volunteers were analyzed. The concentrations of nitrite and nitrate were 0.15 +/- 0.07 mg/L and 3.2 +/- 1.6 mg/L (mean +/- SD), respectively, with a linear correlation in the range of 0.1-50 mg/L. The within-day and between-day coefficients of variation (CVs) for nitrite and nitrate were lower than 5% and 8%, respectively. The recovery was 97-114%. The estimated plasma volume needed for each determination was 108 nL.