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 capi llary zone electrophoresis (CZE) is described. Electrophoresis was car ried out in a 65 cm long, 75 mu m wide silica capillary, using 750 mM sodium chloride containing 5% NICE-Pak OFM Anion-BT (an additive rever sing the electroosmotic flow) as running buffer, at a potential of 20 kV, with on-column W detection at 214 nm. Under these conditions, the two anions migrated in the order of nitrite and nitrate, completely re solved from each other. Forty-one samples of ultrafiltered blood plasm a of healthy volunteers were analyzed. The concentrations of nitrite a nd 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 nit rite and nitrate were lower than 5% and 8%, respectively. The recovery was 97-114%. The estimated plasma volume needed for each determinatio n was 108 nL.