The Determination of Total Nitrite and N-Nitroso Compounds in Atmospheric Samples

Abstract

A group-selective method for the determination of total N-nitroso compounds in air samples was developed. N-nitroso compounds in collected samples are selectively decomposed to yield nitric oxide, which is chemiluminescently detected using a thermal energy analyzer (TEA). The detection system is rapid, reproducible and sensitive, with a detection limit of 0.8 pmol. The method requires only 1–3 microliters of sample extract solution and can be used to analyze aqueous solutions. Nitrites interfere with the determination. However, by analyzing samples before and after treatment with sulfamic acid, total nitrite concentration can be measured from the difference in the two determinations. The analytical technique was applied to the analysis of three collocated samples with a quartz filter followed by an XAD-II trap. The average concentration of total N-nitroso compounds collected on the quartz filters was 12.7 ± 2.4 pmol/m³. The concentration of N-nitroso compounds collected by XAD-II was 19.1 ± 3.3 pmol/m³. The total nitrite concentrations were 28.2 ± 3.4 pmol/m³ and 25.5 ± 18.1 pmol/m³ for material collected on the quartz filter and XAD-II, respectively. A fourth collocated sample spiked with diethylamine on the quartz filter gave higher concentrations of N-nitroso compounds in both the filter and the XAD-II bed. This increase indicates that artifact formation of N-nitroso compounds occurred during sampling. It is recommended that these artifacts be avoided in future sample collection by the use of diffusion denuders to remove the gas phase species before the collection of particles for accurate N-nitroso compounds analysis in ambient air.