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the cryo-focused GC analyses of 5-8 glass beads (as discussed in Chapter 5). The 



technique of simple thermal desorption both from a single glass bead mounted on 

 a probe tip and desorption from multiple glass beads heated in a container in the 

 GC oven was discussed in Chapter 2. The RIC profiles of components desorbed 

 from multiple beads in the apparatus (figure 2-3) depict the leading edge of a 

 selected m/z value when it appears; if the compound is volatile enough, the tailing 

 side of the component peak can also be observed within the time frame of the 

 experiment. The "peaks" appear similar to those observed in frontal 

 chromatography; however, chromatographic separation is not employed for these 

 analyses. Clearly, analysis in this manner will only allow for the possible 

 identification of the more volatile components. The spectra of components desorbed 

 at higher temperatures will include ions from components previously desorbed due 

 to inefficient removal of compounds from the apparatus. 



The use of tandem mass spectrometry was necessary to isolate a particular 

 mass for further fragmentation. The first example using this method is that of 

 ethylene glycol (figure 4-1). Ethylene glycol desorbs off of the glass beads early in 

 the analysis to produce an ion at m/z 63, the [M+H]"^ ion, under PCI conditions in 

 the ion source of the mass spectrometer. Positive identification of this compound 

 was achieved by comparison of the daughter spectrum from handled glass beads (top 

 of figure 4-1) to the daughter spectrum produced by a standard solution of ethylene 

 glycol (bottom of figure 4-1) acquired under identical conditions. 



