185 

 spectra. The cyanides/nitriles located at the end of the table also exhibit an odd 



neutral loss of 27 Da, as well as an even neutral loss of 26 Da from the hydride 



abstracted [M-H]^ parent ion. Both of these classes, which contain a nitrogen in the 



functional group, did not reveal an observable trend from the [M-H]~ parent ions. 



The amino acids did, however, provide information in the negative ion mode due to 



the presence of the carboxylic functional group. The OH~ daughter ion at m/z 17 



was from the [M-H]~ parent ion; a neutral loss of 46 Da (formic acid) occurred from 



the [M+H]"^ and [M-H]"" parent ions. 



The final class to be addressed in the table is the aromatics (i.e. 

 monosubstituted benzenes) for these studies. The base peak in almost all cases was 

 due to the phenyl group. A neutral loss of 78 Da (benzene) was typically seen in 

 daughter spectra produced from the [M + H]"^ ion. Additionally, in positive ion 

 mode, the daughter spectra exhibit the fragmentation pattern of benzene commonly 

 seen in EI mass spectra. 



The information addressed above and found in table 4-2 can now be applied 

 to screening a complex sample. A summary of characteristic neutral losses, derived 

 from the information in table 4-2, appears in table 4-3. The neutral losses are listed 

 (in order of increasing mass) as well as the classes found to be associated with these 

 neutral losses. There is some ambiguity associated with most neutral losses, i.e. 

 more than one functional group may produce a particular neutral loss. It should be 

 reiterated that not all compounds within a given class may exhibit these neutral 

 losses. Additionally, trace components may be difficult to detect with this screening 



