19 

 and a practical view in Chapter 5. The combination of successive stages of mass 



spectrometry (MS/MS) allows for analysis of more complex mixtures with less need 



of prior clean-up of sample and matrix [33]. Reaction studies, compound class 



screening, and elimination of chemical noise via selection of the parent ion of 



interest are some of the advantages attributable to MS/MS. 



Sample introduction 



The sampling methods examined for this work were, for the most part, chosen 

 according to a specific criterion, to allow for sample detection in a fashion similar 

 to that which mosquitoes encounter, i.e. a volatilized sample in the gas phase. 

 Handled glass beads allows attractants present on the skin to be transferred to the 

 glass surface; volatile attractants can then be desorbed by heating the glass. 



Thermal desorption methods . Direct thermal desorption methods, without 

 additional separation or processing, are simple and quick with respect to detection 

 of compounds. The direct insertion probe (or solids probe) allows for samples to be 

 placed through a vacuum lock, directly into the ion source of the mass spectrometer. 

 Normally, a sample is placed in a crucible designed to fit in the end of this probe. 

 For studies in this dissertation, a glass bead fitted onto a glass stem was placed onto 

 the end of the probe. The probe, inserted into the mass spectrometer ion source, 

 is heated to assist in volatilization of compounds off of the bead. 



The idea of heating a single glass bead was extended to multiple beads. Since 

 it is not possible to insert multiple beads directly into the ion source, an alternate 

 method of transferring desorbed volatiles was required. Two to two hundred 



