[Determination of NO2-/ NO3- in exhaled breath condensate. Zinc-catalyzed nitrate reduction]

Analysis of exhaled breath condensate (EBC) is a new prospective method for monitoring of inflammation and oxidative stress in lungs. The most extensively studied exhaled biomarker is nitric oxide (NO). It has very short life span and is converted into nitrites (NO2-) and nitrates (NO3-). In this study the level of NO2- and total level of NO2-/NO3- have been measured in EBC of smokers and non-smokers. Prior determination of NO2-/NO3- the nitrates were reduced to nitrites with zinc, and total level of NO2- was detected by Griess reaction. The mean concentrations of NO2 in EBC of non-smokers and smokers were 2.9 +/- 0.22 Mmol/ vs. 8.5 +/- 1.2 Mmol/l (mean +/- SD, p < 0.001). The level of total nitrites NO2-/NO3- was also higher in smokers (5.65 +/- 0.68 vs. 14.6 +/- 1.43; p < 0.001). Variability index was 8%. Recovery of NO3- from standard solutions was 93.4 +/- 9.6%, and 91.6 +/- 8.9% from EBC. We recommend zinc reduction as good and simple method for NO3- determination in EBC.