87 

 acids was a benefit rather than a hinderance in this case. Based on the thermal 



desorption/cryo-focusing GC results, the aliphatic fatty acids are the most abundant 



components in emanations; their removal permits the analysis of trace level 



components constituting other compound classes. 



Conclusions 



All sampling methods in this section satisfy the initial criterion of sampling 

 volatile emanations in a manner similar to that which mosquitoes encounter. 

 Specifically, this refers to sampling a chemically unmodified sample volatilized into 

 the gas-phase. Direct analysis of a single bead with thermal desorption via the use 

 of a direct insertion probe was found to be inadequate in terms of temporal 

 resolution and the ability to detect trace level components. Tlie use of multiple 

 beads in an enclosed glass sample container increased the sample size for the 

 purpose of detecting trace level components; however, the temporal resolution was 

 even worse than the single bead method due to the headspace volume of the sample 

 container which had to be heated and swept by helium to transfer volatilized 

 compounds onto the column. The problem with poor temporal resolution was 

 resolved via the use of on-column cryo-focusing. This method is used for much of 

 the identification of compounds in Chapter 5. Purge and trap introduction was 

 employed as an alternative method to detect volatile components; furthermore, it 

 discriminates against fatty acids, which are predominant in cryo-focused analyses. 

 This allows for detection of some trace components (low to nonpolar) not readily 



