Determination of nitroaromatic explosive residues in water by stir bar sorptive extraction-gas chromatography-tandem mass spectrometry
Abstract
Nitroaromatic compounds were massively used in the formulation of explosives during both world wars. Even several decades after the end of these wars, their residues are suspected to be widely present in the environment. Their occurrence and effect on ecosystems and human health are still not fully determined. This paper describes the development of a method for the determination of 28 nitroaromatic compounds in water, including isomers of nitrotoluene (NT), dinitrotoluene (DNT), trinitrotoluene (TNT), nitrobenzene (NB), dinitrobenzene (DNB), chloronitrobenzene (ClNB), chlorodinitrobenzene (DNCB), nitronaphthalene (NN), dinitronaphthalene (DNN), nitroaniline (NA), dinitroanisole (DNAN), diphenylamine (DPA), and nitrodiphenylamine (nitro-DPA). In order to separate and individually quantify all the analytes with the best possible sensitivity, stir bar sorptive extraction (SBSE) was chosen as the extraction and pre-concentration step prior to gas chromatography (GC) separation and tandem mass spectrometry detection (MS/MS). Our SBSE optimization efforts focused on parameters such as the type of stir bar, ionic strength, addition of organic solvent, and extraction and desorption times. After these optimizations, the analytical method enabled us to reach limits of quantification (LOQs) between 1 and 50 ng/L in tap water, groundwater, and surface water. The method was applied to the determination of targeted nitroaromatic explosive residues in spring and groundwater samples collected in an area where mine warfare had raged during World War I. Up to 16 different nitroaromatic compounds were detected in the same sample. The highest concentrations were recorded for 2,4-DNT and 1,3-DNB (1700 and 2690 ng/L respectively).