28 

 a fixed mass offset, a neutral loss spectrum can be generated (figure l-3(c)). The 



scan m/z value, for each ion passed through Ql, is offset lower in Q3 by the mass of 



the neutral loss sought. The final scan mode, shown in figure l-3(d), is selected 



reaction monitoring (SRM). The first quadrupole mass filter is set to a selected 



parent ion and the second mass filter is set to a selected daughter ion instead of 



scanning the full mass range. Several such reactions can be monitored sequentially. 



Analysis of Complex Environmental and Biological Samples 



The nature of the work found in this dissertation is similar to some issues in 

 the analysis of environmental and biological samples. TTie approach involving 

 identification of components is similar to methods used for environmental analyses. 

 Modern environmental mass spectrometry is predominantly conducted by GC/MS, 

 with ionization usually accomplished by EI and PCI [57,58]. Although the use of 

 PCI can yield molecular weight information, the use of pulsed positive ion negative 

 ion chemical ionization (PPINICI) allows for greater certainty in identification of the 

 molecular weight of a particular compound [59]. Much of the identification of 

 compounds emanating from human skin reported in this dissertation has involved the 

 use of PPINICI and EI. 



Screening of selected metabolites in a biological matrix, such as urine or 

 blood, provides a rapid method to diagnose disorders in patients [60-62]. 

 Compounds of interest include pesticides, steroids, or drug metabolites [63-66]. The 

 use of MS/MS in the screening process allows for rapid determination with less 



