Nitrate determination in biological fluids by an enzymatic one-step assay with nitrate reductase
Bories, P.N.; Bories, C.
Clinical Chemistry 41(6 Pt 1): 904-907
1995
ISSN/ISBN: 0009-9147 PMID: 7768010 Document Number: 447230
We report a simple, enzymatic, end point method for determining nitrate in serum and urine with use of nitrate reductase from Aspergillus sp. (EC 1.6.6.2). The decrease in absorbance at 340 nm as a result of the oxidation of beta-NADPH is measured. We used FAD as a supplementary electron carrier and added an internal standard to avoid interference from possible inhibitors of the enzymatic reaction. The method was linear from 5 to 200 mu-mol/L nitrate in serum. Within-run (n = 12) and total (n = 14 days) imprecisions (CV) were 5.1-7.7% and 6.29.8%, respectively, at 20-90 mu-mol/L nitrate in serum. Recoveries of added nitrate were 80-106%. The median (range) concentration in serum of 20 healthy subjects was 16 (0-42) mu-mol/L.