|Analysis of volatile compounds in complex samples using static headspace multi-capillary column gas chromatography ion mobility spectrometry (SHS-MCC-GC-IMS)
|Hyphenated Techniques for Comprehensive Analysis
|Prof John Dean
Abstract Information :
This paper will illustrate the positive aspects of the instrumentation, operation and results arising from the application of a static headspace - multi-capillary column gas chromatograph - ion mobility spectrometer instrument used in a variety of projects to analyse volatile (organic) compounds. The instrument is fitted with a static headspace auto-sampler attached to a main unit containing a heated injector, a heated column and the ion mobility detector and associated electronics. The multi-capillary column produces rapid chromatographic separation of volatile components prior to detection by the IMS. The GC column contains ~1000 parallel capillaries, 43 µm ID coated with stationary phase. Retention times are measured in seconds. Sample handling capacity is similar to that of packed columns thereby enhancing method sensitivity. IMS detection is on the basis of drift times measured in milliseconds. Compounds appear as monomers, dimers or trimers at the same retention times but with different drift times. This fact, in addition to the two dimensional separation by retention time and drift time, enhances component characterisation. Data is normally plotted topographically but 3-D plots also make interesting presentations. The use of retention times and the corresponding drift times as co-ordinates of authentic compounds makes possible the preparation of maps simplifying the identification of unknowns.
The presentation will be illustrated by application of SHS-MCC-GC-IMS in a range of complex sample analyses.1-4 The technique allows the analysis and detection of low molecular weight compounds including those containing nitrogen and sulfur; these compounds are often difficult to analyse by other analytical methods. Specific examples will include the profiling and analysis of volatile (organic) compounds as the cause of malodour in laundry, identification and differentiation of Gram positive and Gram negative bacteria3, detection of Listeria species in food applications4, and hydrogen sulfide detection in bacteria.