Ion sampling for inductively coupled plasma mass spectrometry

Olivares, José A.; Houk, R. S.

doi:10.1021/ac00290a054

Cited by 134 publications

(56 citation statements)

References 32 publications

(17 reference statements)

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“…The MPE is a result of two individual components: the mass dependent energy gained in the expansion within the vacuum interface and a fixed component attributable to the plasma potential [29]. Increasing T gas will cause a mass dependent increase of the energy gained during expansion but may as well lower the plasma potential [30] and cause a mass independent reduction of the MPE. The presence of helium may also affect the transmission through the ion optics since the ion energies may be modified differently by collisions compared to argon only as the background gas.…”

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confidence: 99%

Analyte response in laser ablation inductively coupled plasma mass spectrometry

Wang

Hattendorf

Günther

2006

J. Am. Soc. Mass Spectrom.

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The dependence of analyte sensitivity and vaporization efficiency on the operating parameters of an inductively coupled plasma mass spectrometer (ICPMS) was investigated for a wide range of elements in aerosols, produced by laser ablation of silicate glass. The ion signals were recorded for different carrier gas flow rates at different plasma power for two different laser ablation systems and carrier gases. Differences in atomization efficiency and analyte sensitivity are significant for the two gases and the particle size distribution of the aerosol. Vaporization of the aerosol is enhanced when helium is used, which is attributed to a better energy-transfer from the plasma to the central channel of the ICP and a higher diffusion rate of the vaporized material. This minimizes elemental fractionation caused by sequential evaporation and reduces diffusion losses in the ICP. The sensitivity change with carrier gas flow variation is dependent on m/z of the analyte ion and the chemical properties of the element. Elements with high vaporization temperatures reach a maximum at lower gas flow rates than easily vaporized elements. The sensitivity change is furthermore dependent on m/z of the analyte ion, due to the mass dependence of the ion kinetic energies. The mass response curve of the ICPMS is thus not only a result of space charge effects in the ion optics but is also affected by radial diffusion of analyte ions and the mismatch between their kinetic energy after expansion in the vacuum interface and the ion optic settings. T he analytical performance of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analysis is determined by the amount and stoichiometry of the laser generated aerosol as well as by the degree of vaporization, atomization, and ionization of this aerosol in the ICP, and finally the transmission of the ions through the vacuum interface and the ion optics of the ICPMS. The parameters used for laser ablation determine the amount, composition, and particle size distribution of the aerosol released for a given sample [1][2][3]. It has been shown that wavelength, pulse duration, and fluence of the laser beam are the dominating parameters that affect the stoichiometry of the aerosol [2, 4 -6]. Nonetheless, it was found that significant variations in the elemental responses for different elements can be obtained for different ICP operating conditions and for different ICPMS systems, even when stoichiometric sampling from homogeneous (on the scale of the laser spot) samples can be achieved [7][8][9]. These results are currently attributed to incomplete vaporization of the aerosol in the ICP. Particularly when silicate samples are ablated, the aerosol may contain a large fraction of refractory particles and agglomerates above 150 nm in diameter, which are not completely atomized under typical ICP-operating conditions [6,10,11].The particle size distribution of the laser generated aerosol is in the first instance the result of a complex interaction of the laser beam with the sample mater...

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confidence: 99%

Analyte response in laser ablation inductively coupled plasma mass spectrometry

Wang

Hattendorf

Günther

2006

J. Am. Soc. Mass Spectrom.

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“…Despite the brittle nature of silicon, there was no difficulty sustaining a pressure 22 difference between atmosphere on one side of the vacuum interface and high vacuum on the other. Although vacuum packaged silicon devices have been available for many years, this result represents the first demonstration of a differentially pumped MEMS component.…”

Section: Gas Load Partitioningmentioning

confidence: 99%

“…[11][12][13][14][15][16][17] and summaries in [18,19]) and then later for high-speed wind tunnels used for high-speed aircraft testing [20]. Similar methods were then applied to inductively coupled plasma mass spectrometers [21][22][23][24][25][26] and ESI-MS systems [1,[27][28][29][30][31]. In each case, many of the details of the complex shock phenomena involved have been verified by visual observation of flow patterns [13,24, 26] or pressure measurements [25].…”

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confidence: 99%

MEMS-Based Nanospray-Ionization Mass Spectrometer

Wright¹,

Syms

Moseley³

et al. 2010

J. Microelectromech. Syst.

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An electrospray ionisation mass spectrometer (ESI-MS) whose main components are all fabricated using silicon microelectromechanical systems (MEMS) techniques is demonstrated for the first time. The ion source consists of a microengineered alignment bench containing a V-groove mounting for a nanospray capillary, an ion extraction electrode, and a pneumatic nebuliser. The vacuum interface consists of two plates, each carrying a 50 µm diameter capillary, that are selectively etched and bonded together to provide a differentially pumped internal cavity. The quadrupole filter consists of a microfabricated frame that provides mountings for stainless steel rods measuring 650 µm in diameter and 30 mm in length. Two different quadrupoles are compared: a firstgeneration bonded silicon device, and a second-generation silicon-on-glass device with a Brubaker prefilter. Differential pumping of a MEMS component is demonstrated for the first time, atmospheric pressure ionisation and ion transfer into vacuum are characterised, ESI-MS operation is demonstrated and spectra are presented for a variety of compounds. KEYWORDS:Mass spectrometry, Electrospray, Quadrupole filter, MEMS IntroductionOver 25 years have passed since an electrospray ionisation (ESI) source was first coupled to a quadrupole mass spectrometer (MS) by Yamashita and Fenn [1]. Since then, ESI-MS has become a workhorse of analytical chemistry, allowing analytes to be ionised at atmospheric pressure with little fragmentation and passed into a vacuum system for analysis.Conventional ESI sources employ spray tips with an internal diameter (ID) of ≈100 µm[2]. In order to establish a Taylor cone and maintain stable emission of charged droplets, minimum flow rates of 0.5 -5 µL min -1 and voltages of 2.5 -4 kV are used. However, it has been convincingly demonstrated that high sensitivity and stable emission can be achieved at much lower flow rates and voltages using spray tips with IDs of ≈ 5 µm, and silica nanospray capillaries with a range of coatings have become widely available [3][4][5][6][7][8].Unfortunately, while these are inexpensive, operator expertise and costly positioning apparatus are often required for stable and reproducible performance.Electrosprayed ions are passed into a low-pressure chamber via a vacuum interface. The simplest interface is a single orifice or capillary that allows gas and entrained ions to pass directly into the vacuum chamber. Clearly, the orifice must be small enough or the pumps large enough to ensure that the pressure is consistent with mass analysis. However, the susceptibility of very small orifices to clogging and the inconvenience of large pumps led to this approach being abandoned. Modern instruments employ one or more stages of 4 differential pumping. Larger orifices can be tolerated since only a fraction of the flow is transmitted to the vacuum chamber, while the majority of the gas load can be pumped away at higher pressure using more modest pumps.The effective transfer of ions and molecules from atmospheric pressu...

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“…The first ones to have mentioned the space charge effect are Olivares and Houk [20]. This ME involves the positively charged lenses that collect the positive ions, at the exit of the skimmer, by confining them in a beam.…”

Section: Introductionmentioning

confidence: 99%

Effect of Sample Matrix on Radial and Axial Profiles of Ion Abundance in Inductively Coupled Plasma Mass Spectrometry

Mariet¹,

Carrot²,

Moskura³

2011

AJAC

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In inductively coupled plasma mass spectrometry (ICP-MS) analysis, only a few options are available to deal with non-spectroscopic interferences. Considering that diluting the sample is impractical for traces analysis, other alternatives must be employed. Traditionally, the method of standard additions is used to correct the matrix effect but it is a time consuming method. Others methods involves separation techniques. Another way to overcome matrix interferences is to understand the mechanism involved and adjust plasma viewing conditions to reduce or eliminate the effect. In this study, the effect of various concomitant elements in ICP-MS was assessed by measuring the distribution of selected singly charged analyte ions (Al, V, Cr, Mn, Ni, Co, Cu, Zn, As, In, Ba, La, Ce, Pb), doubly charged ions (La, Ce, Ba and Pb) and oxides ions (BaO) in the presence of concomitant elements spanning a mass range from 23 (Na) to 133 (Cs) u.m.a. and different ionization energies. Concomitant elements are alkali metals, alkaline earth metals and Si. Analyte ion suppression was observed while moving the ICP across and away from the sampling interface with or without a single concomitant element. Matrix effect measures were realised, firstly, to highlight the relation between the signal extinction of an analyte and the masse of the concomitant element, and secondly to highlight the relation between the removal of the analyte signal and the first ionization energy of the element of matrix. A dependence upon both the mass of the matrix element and the mass of the analyte was observed. The suppression seems increased with increasing matrix element mass and decreased with increasing analyte mass. The effect of the mass of the matrix element was the more significant of the two factors. If space-charge effects were found to be significant for matrix elements of much lower mass, it seems diffusion also played an active part for heavier matrix elements. Finally, some evidence was found for a shift in ion-atom equilibrium for dications and for energy demand regarding oxides.

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Ion sampling for inductively coupled plasma mass spectrometry

Cited by 134 publications

References 32 publications

Analyte response in laser ablation inductively coupled plasma mass spectrometry

Analyte response in laser ablation inductively coupled plasma mass spectrometry

MEMS-Based Nanospray-Ionization Mass Spectrometer

Effect of Sample Matrix on Radial and Axial Profiles of Ion Abundance in Inductively Coupled Plasma Mass Spectrometry

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