THE ROLE OF NITRIC-OXIDE IN CANCER - IMPROVED METHODS FOR MEASUREMENTOF NITRITE AND NITRATE BY HIGH-PERFORMANCE ION CHROMATOGRAPHY

The short lifetime of nitric oxide (NO) in vivo impedes its quantitati on directly; however, the determination of nitrite and nitrate ions as the end-products of NO oxidation has proven a more practical approach . High-performance ion chromatographic analysis of nitrite in biologic al fluids is hampered by the large amount of chloride ion (up to simil ar to 100 mmol/l) which results in insufficient peak resolution when u tilizing conductimetric detection. Analysis of both anions in small sa mple volumes is also constrained by the need to minimise sample handli ng to avoid contamination by environmental nitrate. We report a means to remove Cl- ions from small sample volumes using Ag+ resin which fac ilitates quantitation of either nitrite and nitrate anions in biologic al samples, using silica or polymer based ion-exchange resins with con ductimetric or electrochemical and spectrophotometric detection. Inclu ding a reversed-phase guard column before the anion-exchange guard and analytical column also greatly extends column lifetime.