39 

 a number of various shapes and volumes of glass sample containers. The enclosed 



vials allowed for heating of the beads for subsequent analysis, usually by cryo- 



focusing or trapping. Cryo-focusing and trapping methods are covered in greater 



detail in Chapter 5. 



Additional experiments conducted with glass beads involved solvent washing 



of the handled beads with methanol. Methanolic solutions were also employed for 



the direct analysis of perspiration via GC and for particle beam/liquid 



chromatography (PB/LC). Work involving solutions is covered in Chapter 3. 



Experimental 



Thermal Desorption from a Single Bead 



Single bead thermal desorption was employed to produce the chromatograms 

 and spectra found in some of the figures in this chapter. The 0.115" (2.9 mm) glass 

 bead was fitted (glass-blown) to a glass stem for insertion into the mass spectrometer 

 ion source. The dimensions of the stem (5 mm long x 1.4 mm diameter) were 

 chosen to fit in the direct insertion probe in place of the typical aluminum crucible. 

 The bead (attached to the stem) was handled for 3-10 min prior to analysis. 

 Handling consisted of rubbing in the palms of the hands only. Subjects for these 

 analyses included the author of this dissertation, Mr. Dan Smith of the USDA, and 

 Dr. Anthony Annacchino, Jr., a former member of this research group. 



Prior to analyses of a handled bead, a blank bead was analyzed to determine 

 the background components. The experimenter who handled the bead then placed 



