9- and 10-Nitro-oleic acid do not interfere with the GC-MS quantitative determination of nitrite and nitrate in biological fluids when measured as their pentafluorobenzyl derivatives

Abstract

The nitrated lipids 9-nitro-oleic acid (9-NO2-OA) and 10-nitro-oleic acid (10-NO2-OA) have been reported to be present in blood of healthy humans. Free and esterified forms of 9-NO2-OA and 10-NO2-OA have been detected in human plasma at about 600 and 300 nM, respectively. These concentrations are of the same order of magnitude of circulating nitrite. In theory, 9-NO2-OA and 10-NO2-OA may interfere with the analysis of circulating nitrite and nitrate. In the present study, we investigated a possible interference of 9-NO2-OA and 10-NO2-OA with the GC-MS method of analysis of nitrite and nitrate involving derivatization by pentafluorobenzyl (PFB) bromide in aqueous acetone at 50 °C for 5 min (nitrite) or for 60 min (nitrite and nitrate). Our results show that 9-NO2-OA and 10-NO2-OA do not interfere with the GC-MS analysis of nitrite and nitrate as PFB derivatives in plasma and phosphate buffered saline when added to these matrices at supraphysiological concentrations of 1-10 μM. Thus, nitrated lipids such as 9-NO2-OA and 10-NO2-OA can be excluded as potential interfering substances in the GC-MS quantitative determination of nitrite and nitrate as their PFB derivatives. © 2007 Elsevier B.V. All rights reserved.