Sprayed liquid-gas extraction in combination with ion mobility spectrometry: a novel approach for the fast determination of semi-volatile compounds in air and from contaminated surfaces

We developed a fast, simple and highly-efficient enrichment procedure for trace levels of semi volatile organic compounds from air and surfaces and combined it with ion mobility spectrometry as field-deployable and rapid analytical technique. Our new technique, the sprayed liquid-gas extraction, was developed and optimized to allow the enrichment of semi volatile organic compounds. The air sample is pumped through a flow blurring nebulizer together with water. The sprayed liquid is collected and the organic compounds are transferred from the water phase to n-hexane via a miniscale liquid-liquid extraction. 50 μL of the n-hexane extract is applied to a fiber tape. After the n-hexane has evaporated, the fiber tape is transferred to the thermodesorber unit of a GDA-X ion mobility spectrometer (Airsense, Schwerin, Germany). The whole sampling and the sample preparation procedure takes no longer than 15 min and only requires 2.5 mL organic solvent. The method was optimized for Malathion, a widely used organophosphate insecticide and an accepted simulant for the nerve-agent, VX. Malathion provides defined ion mobility spectra in both, the positive and negative mode. The positive spectra show one major peak with a reduced mobility of 1.197 cm2 Vs−1 and an additional peak at 1.449 cm2 Vs−1 with lower intensity. A major product ion peak of 1.720 cm2 Vs−1 can be detected in negative mode together with an additional peak of low intensity at 1.403 cm2 Vs−1. The detection limit of the ion mobility spectrometer is approximately 20 ng absolute.

International journal for ion mobility spectrometry 
April 2018

Mashaalah Zarejousheghani, Malcolm Cämmerer, Thomas Mayer, Andreas Walte, Helko Borsdorf