Comparison of high-pressure liquid chromatography (HPLC) and Griess reagent-spectroscopic methods for the measurement of nitrate in serum from healthy individuals in the Nordic countries

Bioavailability of NO can be estimated by measuring the concentration of nitrate (NO 3) in serum. However, the methods used for the measurement NO 3 in plasma or serum show a great degree of variation. Therefore, we compared two analytical methods for the measurement of NO 3 in serum. The concentration of NO 3 in 600 serum samples collected from healthy individuals was determined by the HPLC and by the Griess reagent-spectroscopic method. The concentration of NO 3 in the samples was 29.4 ± 16.1 μmol/L and 26.2 ± 14.0 μmol/L (mean ± SD) measured by HPLC and Griess reagent-spectroscopic method respectively ( p < 0.0001). We detected a significant correlation between the two methods ( R = 0.81, p < 0.0001). A significant correlation between the two methods may suggest that either method can be used for the measurement of NO 3 in serum, however the Griess reagent-spectroscopic method measures lower concentrations of NO 3 than the HPLC method.