292 

 alone. There were, however, components that failed to give useful fragmentation 

 patterns in one or more of these modes, preventing confirmation of presence of a 

 compound or in some cases (at least 37) prevented even a speculative estimate of 

 compound identity. There were also cases where compounds were identifiable by 

 PPINICI and/or by EI analysis; however, upon background subtraction, valuable 

 fragmentation information was lost due to coelution of sample components. Tandem 

 mass spectrometry could be employed to obtain daughter spectra of the selected 

 molecular ion, protonated molecular species or deprotonated molecular species to 

 assist in the identification process. There were cases where both the molecular ion 

 (EI) and protonated or deprotonated species (CI) were absent; the use of a reagent 

 gas with lower proton affinity is recommended for PCI to obtain "softer" ionization. 

 Attempts at employing CO, as a reagent gas were not successful in this case; 

 however, should this be of interest in the future as a potential reagent gas, the 

 background is covered in the appendix to this dissertation. 



The final two studies to be discussed involve the most complex and intricate 

 arrangements. On-line monitoring by mass spectrometry and olfactometer would be 

 advantageous (analogous to organoleptic evaluations used in the fragrance industry). 

 This application was discussed briefly in Chapter 1. The problems to overcome with 

 respect to analyses of this type would be location of both the mass spectrometer and 

 olfactomer, and more importantly, the ability of mosquitoes to respond to successive 

 stimuli should that occur. Mosquitoes may be desensitized by certain compounds. 



