Optimization of Single-Step Assay for Circulating Nitrite and Nitrate Ions (NOx) as Risk Factors of Cardiovascular Mortality.

We propose an optimized single-step assay of total nitrite and nitrate concentrations based on serum deproteinization by ultrafiltration. After deproteinization, the residual protein concentration was 0.0800±0.0007 mg/ml, which secured necessary transparency of the specimens in contrast to methanol deproteinization. The optimized assay for serum nitrite and nitrate ions is characterized by high reproducibility and accuracy (variation coefficient <7%) and can be recommended for routine use in clinical practice.