Pyrolysis GC-IMS Methods

FIGURE 18.8 Topographic plots of compensation voltage versus retention time from the Py-GC-DMS characterization of positive ions for E. coli (a). Micrococcus luteus (b), and B. megaterium (c). The intensity scale ranges from 0.9 V (white) to 2.5 V (black) in equal steps of 0.1 V. (From Schmidt et ah, Microfabricated differential mobility spectrometry with pryrolysis gas chromatography for chemical characterization of bacteria, Anal. Chem. 2004, 76, 5208-5217. With permission.) 

Thermal desorption with an Itemiser IMS detection and chemometric modeling were deployed to characterize and differentiate between whole-cell bacteria. In situ hydrolysis and methylation were required to differentiate Escherichia coli strains that could not be distinguished by their mobility spectra. The metabolic profile of 

Escherichia coli was characterized by IM(TOF)MS with a MALDI source and with an ESI source. . The preseparation afforded by the mobility spectrometer made it possible to separate metabolites in the mass range below 1,800 Da. ESI-IMS was also used to characterize intact virus particles, and it was found that icosahedral virus particles retain their structure in the gas phase.  

The ability of a DMS to detect pyrolized spores of Bacillus subtilis (a stimulant for Bacillus anthracis) was demonstrated, even when the spores were suspended in water ll The spores had to heated to quite high tanperatures (above SSO C for at least 10 s) to produce fragment particles considerably below 10 kDa. 

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