Pulsed glow discharge in thin-walled metallic hollow cathode. Analytical possibilities in atomic and mass spectrometry

Abstract

In this article investigation of atomization and ionization processes in pulsed glow discharge with atomic absorption and mass spectrometry is reported. It was shown that sample sputtering and atomization in a thinwalled metallic hollow cathode (TMHC) is highly efficient in pulsed glow discharge plasma. Using a TMHC as an atomizer with a Zeeman AAS system a background absorption influence for samples with high matrix concentration was significantly reduced compared with graphite furnace AAS. This effect is attributed to the high efficiency of dissociation of matrix components in pulsed glow discharge. TMHC was also used as an ion source for an analytical system with time-of-flight mass-spectrometry (TOF-MS). Ionization processes in pulsed glow discharge were theoretically simulated using modified algorithms and the results of the simulation were experimentally confirmed. It was shown that Penning ionization significantly contributes to ionization yield even after pulsed discharge termination. Sample sputtering dynamics for different discharge regimes were explained and transportation processes from TMHC to TOF-MS were optimized. Limits of detection for Cd and Cu were 20 and 15 ng l 21 , respectively.

Model of microsecond pulsed glow discharge in hollow cathode for mass spectrometry

“…10, 12) that there is a temporal separation of Ar + and sample ions because Ar atoms are not subject to Penning ionization. This is in a qualitative agreement with experimental works [13,19,21,60], where the temporal separation was observed experimentally. …”

“…This mass spectrometer uses HC PGD as the source of ions. Several types of hollow cathodes may be installed in the system: a thin-walled monolithic hollow cathode [21] for dry residues analysis, monolithic thick-walled and combined cathodes for solid sample analysis [24]. In this article only the thin-walled monolithic HC and the combined one are considered because typical parameters, and therefore the main processes, for the thick-walled HC and the combined one are the same.…”

“…To avoid difficulties with the combination of these submodels, we have developed another model based on the Monte-Carlo method for all particles in the discharge and continuity equations in the afterglow. This model in early stage of development was described in [20,21]; in this article a detailed description and application of the model is given.…”

“…In the last decade HC PGD has been investigated as a source of ions for mass spectrometry [15,16,[19][20][21][22][23][24]. Application of HC in the pulsed mode leads to a combination of the advantages: higher sensitivity, possibility for direct analysis of conducting, semi-conducting and insulating materials [3,24], high rate of excitation and ionization of the sample atoms.…”

New μs-pulsed DC glow discharge assembly on a fast flow high power source for time resolved analysis in high resolution mass spectrometry

“…To reduce plasma based interferences we can just sum the points during the interval 100 to 300 ms after the start of the pulse. For example it can be used to reduce the abundance tail from the 40 Ar 16 O + from 56 Fe + . It should be noted that this only helps with oxygen inside the plasma, for instance residual atmospherics from vacuum leaks, but not from the sample itself.…”