DETERMINATION OF NITRITE AND NITRATE IN HUMAN SERUM

A simple and effective assay for nitrite and nitrate in human serum ha s been developed using ion chromatography. Initial experiments using i socratic carbonate-bicarbonate elution with conductivity detection on a Dionex QIC system with an AS4A-SC column showed promise but were uns atisfactory because of co-elution problems with nitrite. Carbonate and chloride were investigated as eluents using a gradient system, and di rect UV detection at 214 nm was used in place of conductivity detectio n. Dionex AS4A, AS9A, AS12, Nucleopac PA-100 and Carbopac PA-100 colum ns were compared for selectivity and resistance to overload. The final method, using a chloride concentration gradient, pH buffering and dir ect UV detection with a Carbopac PA-100 column, shows good resolution, does not suffer from chloride overload and is simple to use. The meth od is being used in an investigation of the role of nitric oxide in pr e-eclampsia, a hypertensive disorder during pregnancy.