Sequential injection analysis of nitrites and nitrates in human serum using nitrate reductase

Area of Science:

• Clinical Chemistry
• Analytical Chemistry
• Biomedical Engineering

Background:

• Nitrates and nitrites are key biomarkers in human serum, reflecting nitric oxide metabolism and disease states.
• Accurate quantification of these analytes is crucial for clinical diagnostics.
• Traditional methods can be time-consuming and require larger sample volumes.

Purpose of the Study:

• To develop and validate a novel sequential injection analysis (SIA) flow system for the rapid determination of nitrates and nitrites in human serum.
• To assess the efficiency, accuracy, and sample/reagent economy of the developed SIA method compared to conventional techniques.

Main Methods:

• A sequential injection analysis (SIA) system was employed for automated fluidic manipulation.
• Nitrite was directly measured using the Griess reagent.
• Nitrate was quantified after enzymatic reduction to nitrite using nitrate reductase and NADPH.

Main Results:

• The SIA method achieved high sensitivity with detection limits of 0.14 mg/l for nitrates and 0.03 mg/l for nitrites.
• Accurate measurements were obtained for serum samples with relative standard deviations below 5%.
• The SIA system demonstrated excellent agreement with a standard batch procedure for deproteinized serum samples.

Conclusions:

• The developed automated SIA method provides a rapid and efficient alternative for routine clinical analysis of serum nitrates and nitrites.
• This method significantly reduces sample volume, reagent consumption (nitrate reductase), and analysis time compared to traditional methods.
• The SIA system offers a practical and cost-effective solution for disease marker monitoring.