97 



Analysis of Methanolic Perspiration Solution 



The perspiration samples were analyzed by dissolving approximately 150 p,L 

 of forehead perspiration (from the author of this dissertation) in 3 mL of methanol. 

 The mixture separated into two phases after allowing it to sit overnight. One ^L of 

 each phase was injected onto a 10.5 m x 0.178 mm i.d. DB-5 FSOT column (df=0.4 

 nm). The injection port temperature and transfer line temperature were set 

 isothermal at 250°C and 200°C, respectively. The GC oven was held at SO^C for 0.25 

 min after injection, then ramped at 30°C/min for 4.0 min up to 150°C and held for 

 0.25 min. The GC was run in splitless mode, with the split valve opening after 0.2 

 min. The column carrier gas was helium at a head pressure of 8 psig. The ion 

 source temperature was set at 150°C and the manifold temperature was set at 70°C. 

 NCI was accomplished with methane at an indicated source pressure of 1695 mtorr. 

 The filament emission current was set to 200 jiA with an electron energy of 100 eV. 

 Scanning with a 0.5 s scan time over Ql was used to obtain all data. The conversion 

 dynode was set at +5 kV for the collection of negative ions. The electron multiplier 

 was set to -1000 V. 



Results and Discussion 



Reactions of Lactic Acid 



Negative chemical ionization with methane as the reagent gas leads to the 

 formation of negative ions by two main processes [33,72,74]. The formation of a 



