161 

 For liquid-phase standards, approximately 250 ^L was diluted in methanol in a 100 



mL volumetric flask. The standards employed were acrolein, acetone, acetic acid, 



ethylene glycol, pyruvic acid (sodium salt), DL-a-alanine, oxalic acid, glycerol, 



benzaldehyde, anisole, malonic acid, acetophenone, sec-butylamine, 2-butenal, 1,3- 



butanediol, 1,4-butanediol, benzoic acid, cyanoacetic acid, benzyl alcohol, 



benzonitrile, benzamide, 1-butanol, 1-decene, diethylene glycol, Ai-decane, dodecane, 



L-leucine, diethylamine, glycine, tetradecanoic acid, 2-butanone, phenol, styrene, 1- 



pentanol, 2-pentanone, vinyl acetate, sebacic acid, octadecanoic acid, tartaric acid, 



and toluene. 



Each standard solution was injected (0.5 ^iL) onto a 10.5 m x 0.178 mm i.d. 

 DB-5 FSOT column (df=0.4 ^m). The GC injection port was set at 250°C and the 

 helium carrier gas head pressure was set at 4 psig. The column oven was ramped, 

 after an initial 1.0 min hold at 30°C, up to 210°C at 15°C/min, then held at 210°C for 

 5 min. The transfer line was concurrently ramped from 50°C to 215°C at 20''C/min 

 once the run was started, and held at 215°C for the remainder of the analysis. 



Sample ionization was effected by PCI and NCI with methane reagent gas at 

 an indicated source pressure of 1700 mtorr. The ion source was set at 150°C and the 

 manifold set at 70°C. The electron energy was set at 100 eV and the filament 

 emission current at 200 ^lA. The collision gas was argon at an indicated pressure of 

 1.5 mtorr; the collision energy was 15 eV. The electron multiplier was set at -1200 

 V and the conversion dynode set at +5 kV for negative ion detection and -5 kV for 

 positive ion detection. Daughter spectra were acquired at the rate of 1 s per scan. 



