The pulsed glow discharge (GD) plasma source exhibits several characte
ristics that make it ideally suited for use with time-of-flight mass s
pectrometry (TOFMS), TOFMS uniquely affords the ability to monitor a n
arrow temporal window for a time-varying process such as ion formation
in the pulsed glow discharge plasma. Pulsed GD-TOFMS exhibited distin
ct advantages for the direct determination of trace elements in solid
state samples, Initially, the pulse-powered GD-TOFMS system used for t
hese investigations exhibited poor resolution, In an effort to improve
resolution, a slit was introduced to narrow the ion beam orthogonally
entering the extraction region of the TOFMS. In an effort to determin
e optimal operating conditions, the influence of slit width on TOF per
formance was investigated. In the course of this study, the slit width
was found to influence isotope ratio accuracy as well as resolution,
A slit width of 1.0 mm was determined to provide the best compromise b
etween resolution and isotope ratio accuracy. Pulsed GD-TOFMS affords
improved sensitivity and selectivity because Penning ionization is enh
anced during the time period immediately following the termination of
the discharge power. Ions sampled by an extraction pulse applied after
power termination also yield a mass spectrum that is free of contribu
tions arising from electron-ionized interferences, This advantage aris
es because only ions generated via the Penning ionization mechanism pe
rsist after the termination of discharge power. Sampling in the ''afte
rpeak'' time regime eliminates the saturation of the detector arising
from discharge support gas ion signal.