Near real-time VOCs analysis using an aspiration ion mobility spectrometer.

The ChemPro 100i chemical detector (aspiration-type ion mobility spectrometer) was used for the detection of selected volatile organic compounds known to be potential indicators of human presence. The targeted group of compounds mainly comprised ketones (acetone, 2-butanone, 2-pentanone, 3-methyl-2-butanone, 4-heptanone), aldehydes (propanal, pentanal, hexanal, octanal), dimethyl disulfide (DMDS), isoprene and ethanol. Gaseous standards of these compounds were produced from pure substances and analysed using the aspiration ion mobility spectrometry (AIMS) chemical detector. The chemical fingerprints obtained (patterns) were compared to evaluate possible differences in responses. The limits of detection ranged from 5 ppbv for 4-heptanone to 87 ppbv for DMDS, whereas relative standard deviations varied from 1.5% to 5%. Additionally, quantitative AIMS measurements of acetone levels in human breath samples were carried out. The breath acetone levels measured with AIMS ranged from 290 to 540 ppbv and correlated quite well with the SPME-GC-MS results, showing limited potential of AIMS for the detection of breath acetone; however, deviations were observed for concentrations above 500 ppbv. The further success of AIMS in breath analysis depends on improvements of the analytical power (e.g. selectivity, sensitivity, resolution) and the implementation of multivariate data analysis techniques.