219 

 Other characteristic ions or fragments were not examined unless an unknown 



mass spectrum failed the library search. In general, examination of isotope peaks for 



halogen-containing compounds was not necessary due to the library database readily 



identifying the halogenated compounds. Mass spectra which the library targeted as 



sulfur-containing compounds were visually inspected for the presence of a loss of 34 



Da (characteristic of thiols) as well as the presence of the series m/z 47, 61, 75, 89, 



.... Mass spectra of suspected aldehydes, ketones, or aliphatics were examined 



when needed for the presence of the series m/z 15, 29, 43, 57, . . . as well as for 



losses of 1, 18 and 28 Da from aldehydes. Mass chromatograms were examined for 



the McLafferty rearrangement ion for aldehydes at m/z 44, as well as for ions at m/z 



58 and m/z 72, which could be indicative of a methyl and ethyl ketones, respectively; 



however, it should be noted that the m/z 58 ion also results from amines. Alcohols 



of five or more carbons display [M-IS]"^ and [M-46]'*" ions; however, acids may yield 



these ions also. Instead, analysis of the corresponding peak in NCI for the presence 



of an [M-H-Hj]^, as described in the NCI section, was employed for suspected 



alcohols. Mass chromatograms for the m/z 77 ion or cluster of ions within 2 mass 



units were examined to determine the presence of aromatics. Mass spectra were 



examined for an [M-27]* ion when an amine was suspected, as well as the even ion 



series of m/z 44, 58, 72, 86, . . . which is characteristic of amines. 



