40 

 the bead onto the solids probe for analysis. The solids probe containing the bead 



was inserted into the mass spectrometer ion source. The probe ramp consisted of 



increasing the temperature from 50°C to 300°C over a six minute period. 



The mass spectrometer was a Finnigan MAT TSQ70 triple quadrupole mass 



spectrometer equipped with a Varian 3400 gas chromatograph. TTiis modified 



instrument contains an octopole for Q2 and a 20 kV dynode. The instrument was 



employed only for single-stage (MS) detection. The filament emission current was 



set to 200 p,A in all cases. The electron energy was 70 eV for EI analyses and 100 



eV for CI analyses. The manifold temperature was set to 70°C while the ion source 



temperature was set to 150°C for CI and 170°C for EI. The mass ranges scanned 



were m/z 10-650 for EI and m/z 60-650 for CI. The reagent gas for CI analyses was 



methane; the indicated pressure of methane in the ion source was 1650 mtorr. The 



electron multiplier was set between -1000 and -1200 V and the conversion dynode 



set at -5 kV. Prior to data acquisition, the instrument was tuned for maximum 



transmission of characteristic ions from perfluorotributylamine (PFTBA). 



Thermal Desorption from Multiple Beads 



The sampling of multiple beads is not amenable to solids probe introduction 

 via insertion through the probe lock of the mass spectrometer. Initial sampling of 

 multiple beads was accomplished by the apparatus shown in figure 2-3. The beads 

 were placed in a round bottom flask; a 100 mL or 250 mL round bottom flask 

 modified for use with this apparatus. The modification consisted of removing the 



