Some fundamental characteristics of a reduced-pressure plasma extracted from an inductively coupled plasma

Lim, H. B.; Houk, R. S.; Edelson, M.C.; Carney, Kevin

doi:10.1039/ja9890400365

Cited by 29 publications

(8 citation statements)

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“…Measurements of T gas in a Mach disk (not quite the same thing, as no skimmer was present) gave values of ~ 3000 K [39]. We therefore estimate T gas in a shock wave to be 2000 to 3000 K. If the shock wave is hotter than this estimate, the resulting T gas will be closer to that of the ICP.…”

Section: Effect Of Assumed Neutral Gas Densities On Diagnosis Of Ion mentioning

confidence: 95%

High Resolution Studies of the Origins of Polyatomic Ions in Inductively Coupled Plasma-Mass Spectrometry

Ferguson

2006

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In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Therefore, the use of collision cells is not a complete treatment for the polyatomic problem. UMICollision cells are a useful tool, but only under certain circumstances. Cool PlasmaAnother alternative is using a "cool" plasma, i.e. a lower RF power, higher nebulizer gas flow rate, and sampling position farther upstream. This technique is particularly helpful when Ar + , ArH + , or ArO + are an interference, as in the analyses of potassium, calcium, and iron. However, cool plasmas inefficiently ionize elements with a high ionization potential, such as selenium. This technique also tends to increase the abundance of refractory oxides and analyte hydrides [2, 3]. Cool plasmas are suitable as a sample specific tool for controlling polyatomic interferences. Solvent RemovalReducing the solvent load introduced to the plasma can reduce the abundance of many polyatomic ions. Alternate Stability RegionsAlternate stability regions provide improved mass resolution for quadrupole devices, which in turn allows for separation of some interferences from analytes of interest. However, the resolutions reached are still inferior to those provided by a sector field device. In addition, operation in alternate stability regions results in reduced sensitivity and increased background levels [2], The higher RF power required for the use of alternate stability regions also limits the feasibility of the technique. The use of alternate stability regions is not a panacea for the polyatomic ion issue. Cone Composition and GeometryAnother way that researchers have tried to reduce polyatomic ion formation is through modification of the sampler and/or skimmer cones. Helal and coworkers have studied the influence of skimmer materials on the formation of polyatomic ions [5], While using a copper skimmer cone plated with gold, they monitored polyatomics that would be 4 expected to form, such as ArX + , XO + , and XN + , where X indicates Cu or Au. The signal from each polyatomic ion was compared for Cu and Au. It was found that the gold was more likely to create the expected interferences than copper, and as the gold was stripped off the outer surface of the cone, the gold interferences were reduced. Over the course of forty minutes, the ratios of the copper and gold interferences neared one [5]. This result shows the impact of cone material in polyatomic ion formation.Other variables that can impact the formation of polyatomic interferences are aperture size, cone spacing, and angle design. The aperture size should be maximized to allow for the greatest analytical signal and to avoid clogging, however the size is limited by the pumping capability, as the interface region should maintain a pressure of about 1-4 Torr [6],Typically, this maximum size is reached in the 0.7 to 1.0 mm range. Oxide formation increases with a decrease in ...

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Section: Effect Of Assumed Neutral Gas Densities On Diagnosis Of Ion mentioning

confidence: 95%

High Resolution Studies of the Origins of Polyatomic Ions in Inductively Coupled Plasma-Mass Spectrometry

Ferguson

2006

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“…[43][44][45][46][47][48][49][50][51][52] However, most have assumed that the interface has little if any effect on the plasma upstream from the vacuum-sampling process. [53][54][55] In order to investigate this assumption in more detail, we have applied our diagnostic techniques to an ICP in contact with a vacuum interface patterned after ones usually employed in ICP-MS. 56 The position of the vacuum sampling cone was 13 mm above the load coil (ALC), and Thomson scattering, Rayleigh scattering, and line-of-site emission measurements were made at several locations between the top of the torch and the sampling cone and at several different central-gas flow rates.…”

Section: Effect Of An Icp-ms Sampling Cone On Plasma Featuresmentioning

confidence: 99%

Toward a Fuller Understanding of Analytical Atomic Spectrometry

et al. 2002

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“…In 1978, the first analytical mass spectrometer with an ICP ion source was developed in Ames Laboratory and a paper ! was published in 1980 by Houk et al (4). Even though the development of ICP-MS was more derived from atomic spectroscopy rather than from mass spectrometry, the earlier experience in extracting other plasmas and neutral beams with mass spectrometry are important in the instrument design.…”

Section: Icp-ms Instrumentation and Developmentmentioning

confidence: 99%

“…The arrangement was similar to that used in other atmospheric pressure ion sources (86,87,88,89,90). However, condensed solids readily plugged the pinholesized orifice when real samples were analyzed, and levels of metal oxide ions were high (4,20,21,22). As soon as the diameter exceeded 120 pm a discharge formed near the orifice.…”

Section: Plasma Extraction Processmentioning

confidence: 99%

“…Physical interactions such as recombination, reflection and collision will also happen on the interface wall. When the pinhole-sized sampler orifice was used (< 100 pm) in the early instrument design, it was mainly the boundary layer that was sampled into the vacuum system for mass spectrometric analysis (4,16,17). It is undesirable that the oxide species formed in the boundary layer surrounding the orifice are extracted into the mass spectrometer.…”

Section: Effects Of Boundary Laver Formationmentioning

confidence: 99%

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Fundamental studies of the plasma extraction and ion beam formation processes in inductively coupled plasma mass spectrometry

Niu

1995

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Some fundamental characteristics of a reduced-pressure plasma extracted from an inductively coupled plasma

Cited by 29 publications

References 0 publications

High Resolution Studies of the Origins of Polyatomic Ions in Inductively Coupled Plasma-Mass Spectrometry

High Resolution Studies of the Origins of Polyatomic Ions in Inductively Coupled Plasma-Mass Spectrometry

Toward a Fuller Understanding of Analytical Atomic Spectrometry

Fundamental studies of the plasma extraction and ion beam formation processes in inductively coupled plasma mass spectrometry

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