Simultaneous analysis of nitrite, nitrate and the nicotinamide nucleotidesby capillary electrophoresis: Application to biochemical studies and humanextracellular fluids

A simple but rapid capillary electrophoresis method was developed for the m easurement of nitrite and nitrate in human extracellular fluids and other a queous solutions. The capabilities of the method were demonstrated by the m easurement of endogenous nitrite and nitrate in plasma and serum samples fr om healthy volunteers, and serum and synovial fluid samples from rheumatoid arthritis patients. Furthermore, this method was used to simultaneously me asure nicotinamide adenine dinucleotide, reduced (NADH), nicotinamide adeni ne dinucleotide (NAD(+)), nitrite, and nitrate, when studying the nitrite r eductase activity of xanthine oxidase. The stability of nitrite was also in vestigated and it was found that when whole blood was spiked with nitrite a nd then processed, the nitrite was more stable in the plasma than in the se rum. Our findings may help to explain the variations in basal nitrite conce ntrations reported in the literature.