The potential of a modified rf glow discharge source for enhanced elemental speciation studies

Abstract

Radio frequency glow discharge source mass spectrometry (rf GDMS) was employed for determination of tetramethyltin (TMT) with axial sample introduction via capillary gas chromatography (GC). The axial cell design provided homogenous sampling independent of the transfer line capillary position by eliminating discharge asymmetry. Sensitivity value for TMT of 2237 counts pg 21 was achieved with the current setup, a nearly three-fold improvement from a previous study (681 counts pg 21 ). The 120 Sn + ion signal increased with pressure and decreased with rf power. TMT mass spectra with fragment ion signals comparable in intensity to the 120 Sn + ion signal were obtained. The ion signal ratio ( 120 Sn + ion intensity/fragment ion intensity) was monitored as a function of expansion stage pressure of the mass spectrometer to access the extent of molecular fragmentation with variable plasma conditions.

Mixed Gas Helium/Argon Low-Power/Reduced-Pressure ICP as a Tunable Ionization Source for the Mass Spectrometric Detection of Organotin Compounds

“…Due to the relatively large sampler ori ce, the pressure measured in the expansion stage of the m ass spectrometer was considered to be a good estimate of the cell pressure for the LP/RP-ICP, as in previous studies. 4,11,12 G C-LP/RP-ICP Interface. A diagram of the interface has been shown in detail in previous studies.…”

“…This pressure was used to collect mass spectral data in the time-resolved data acquisition m ode (TRA). Table I lists 12 In the current study, pressure was varied for an LP/RP-ICP cell, and the effects on the fragm entation of TET were obser ved. Figure 1 shows that the intensities of the fragm ent ions, relative to the elemental ion for TET for the He LP/ RP-ICP, are greater at lower pressures, thus illustrating a trend similar to that found by Belkin et al 12 The sensitivity at these lower pressures, however, is slightly worse for the elemental ion as well as for the fragment ions.…”

“…Belkin et al recently studied a modi ed rf-G D source and obser ved tunable m olecular fragm entation of tetramethyltin (TMT) by varying the expansion stage pressure of the mass spectrometer. 12 W hile reduced-pressure Ar and He ICP sources have been used previously for speciation studies, a m ixed LP/ RP-He/Ar ICP has not been studied for this purpose. In the current study, it was of interest to obser ve any tunability for organotin molecular fragmentation as a function of the amount of argon gas added to an LP/RP-He ICP.…”

Organic mass spectrometry and control of fragmentation using a fast flow glow discharge ion source

“…Since the late 1980s attention has been given to developing the glow discharge for the analysis of organic compounds 2–14. Glow discharge sources have been used as element‐specific detectors for gas chromatography (GC), with particular emphasis on applications in speciation studies 15.…”

“…The ionizing capabilities of the glow discharge lies between these two extremes of conventional atomic and molecular ion sources. The number of papers describing the glow discharge as an element‐specific detector for GC is small by comparison to ICP‐MS; however, it does show promise as a ‘tuneable’ plasma source,17 and has been investigated by a number of groups 4–14. The discharge conditions (i.e.…”