92 



energy was set at 100 eV for CI conditions and the filament emission current set at 



200 tiA. The collision gas was nitrogen with an indicated pressure of 1.97 mtorr in 

 the collision cell; the collision energy was typically 9 eV. The electron multiplier 

 setting was -1200 V with the dynode set at +5 kV. Data were collected employing 

 various MS/MS scan modes, indicated in the figure captions, with a scan time of 3 

 s per scan. 



Some experiments in this section employed cryo-focused GC/MS analysis of 

 5 beads; the beads were rubbed for 5 min in the palms of the hands by the author 

 of this dissertation. The beads were placed in a reversed GC injection insert, as 

 described in Chapter 2. The injection port was ramped from 25°C to 250°C over 7.5 

 min and held at that temperature for an additional 2.5 min. Compounds desorbed 

 from the beads were cryo-focused in the first 40 cm of column in the GC oven 

 throughout the injection port heating period. Prior to beginning the oven ramp for 

 analysis, the cup of liquid nitrogen was removed. The ramp consisted of a 1.0 min 

 hold at 25°C, a 12 min ramp at 15°C/min up to 210''C, and a final hold at 210°C for 

 5.0 min. The transfer line was concurrently ramped, after a 1.0 min hold at 40°C, 

 up to 225°C at 15°C/min, and held at 225°C for 5.0 min. The separation was effected 

 on a 20 m X 0.25 mm i.d. Carbowax column (d[=0.25 p,m). Positive and negative ion 

 data were acquired with methane at 1660 mtorr (indicated) using PPINICI. The ion 

 source and manifold temperatures were 150°C and 70°C, respectively. The electron 

 energy was 100 eV with the filament set at 200 p.A. The Q3 scan time was 2 s per 



