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 involved the volatilization of lactic acid to the gas phase via desorption. This is a 



necessity for subsequent mass spectrometric analysis, as well as for mosquito 



detection of lactic acid which has evaporated off of the skin. This is the equilibrium 



represented by the double arrow between the aqueous and gaseous forms of lactic 



acid. Addition of heat to this system favors the volatilization of lactic acid. 



Oligomerization reactions of lactic acid in the gas phase were discussed 

 previously. This process can also occur in the condensed phase as represented by 

 the double arrow leading from lactic acid to (HA)„ (s,l). This process occurs at high 

 concentrations of sample in the ion source. 



There is an acid dissociation equilibrium in the condensed phase governed by 

 this K^ between the associated lactic acid and the dissociated form (free hydrogen 

 ion and lactate ion). In the dissociated form, the lactate ion is not susceptible to 

 volatilization; thus, detection of lactate by mosquitoes via olfaction cannot exist. 

 Recalling LeChatlier's principle, this system can be affected by the hydrogen ion 

 concentration, [H^]. Upon acidification, the system will move towards formation of 

 associated lactic acid, increasing volatility. The removal of free [H^] via addition of 

 base shifts the equilibrium towards the production of dissociated lactate. This will 

 decrease the free acid available for volatilization, thereby decreasing attraction via 

 mosquito olfactory cues. 



There was an additional condensed-phase concern besides implications of 

 acidAiase effects on mosquito attraction. This was the possibility of additional 

 species produced by reactions occurring in the condensed phase. The possibility of 



