157 

 daughter library to aid in spectral interpretation and in screening for compound 



classes via examination of specific neutral losses. The final section examines the use 



of selected neutral losses for rapid screening for compound classes present in the 



emanations of a human subject. 



Analysis of Multiple Beads Without GC Separation 



Tandem mass spectrometry was initially employed in this work for the 

 identification of compounds desorbed from multiple beads in a glass chamber. The 

 lack of GC separation and poor temporal resolution achieved by simple desorption 

 of volatiles off of glass beads necessitated the use of some means of additional 

 selectivity (see Chapter 2). The use of a second stage of mass spectrometry provided 

 the means for mass analysis of one selected mass of interest; however, similar 

 compounds which fragment to yield the selected mass, or compounds with identical 

 parent mass to the selected ion, complicated the mass spectral interpretation. This 

 made GC separation attractive for further identification of components emanated 

 from the skin. 



Daughter Library 



The focus of the second part of this chapter is the compilation of a daughter 

 library under a set of conditions chosen to be constant throughout this work. The 

 collision cell offset, collision gas, and collision gas pressure affect the degree of 

 fragmentation via collision energies, collision processes, and numbers of collisions 



