Rapid quantification and screening of nitrogen-containing rocket fuel transformation products by vortex assisted liquid-liquid microextraction and gas chromatography – high-resolution Orbitrap mass spectrometry

Abstract

Existing and newly developed technologies for clean-up of wastewaters and soils contaminated with rocket fuel unsymmetrical dimethylhydrazine (UDMH) are based on the oxidative treatment, as well as gasification in supercritical water. Being easily transformed by a radical mechanism, UDMH is capable of producing an extremely wide range of potentially hazardous nitrogen-containing products. Their identification and simultaneous quantification at low concentrations in water samples by gas chromatography is a challenging task requiring a matrix change. We proposed a combination of dispersive vortex-assisted liquid-liquid microextraction (VALLME) of analytes followed by gas chromatography – Orbitrap mass spectrometry allowing simultaneous target analysis and non-targeted screening. Dichloromethane and chloroform provided rapid (10 min) and effective extraction of most of UDMH transformation products. The maximum recoveries were achieved by alkalizing and saturating the aqueous samples with ammonium sulfate. The use of pyridine‑d5 as an internal standard allowed developing an approach to the simultaneous determination of 24 compounds of various classes with detection limits for the most analytes in the range 0.02–1.1 μg L−1 and accuracy of 81–117% with low-cost, simple, and rapid sample preparation procedure. Extraction with a 100 µL of chloroform allowed further increasing sensitivity up to one order of magnitude and attaining LOD values for 20 compounds in the range of 0.002–0.1 μg L−1 comparable with that obtained by vacuum-assisted headspace solid-phase microextraction. The developed method was validated and tested for the analyses of real samples – degraded aqueous solution of rocket fuel, products of UDMH treatment in supercritical water and aqueous extract of soil from the place of carrier rocket accidental crash. Twenty-nine compounds that were not previously described as UDMH transformation products were tentatively identified.