Dissociation of polyatomic ions in the inductively coupled plasma

Houk, R. S.; Praphairaksit, Narong

doi:10.1016/s0584-8547(01)00236-1

Cited by 71 publications

(66 citation statements)

References 62 publications

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“…However, the temperature dependence of the constant is determined through use of the partition functions associated with each species involved. 7,23 This in turn requires knowledge of energetic and structural data for each species. Since many polyatomic ions are not very abundant or long-lived, much of this data cannot be easily obtained through experiment.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Investigation of Small Polyatomic Ions Observed in Inductively Coupled Plasma Mass Spectrometry: H_xCO⁺ and H_xN₂⁺ (x = 1, 2, 3)

et al. 2008

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Two series of small polyatomic ions, HxCO+ and HxN2+ (x = 1, 2, 3), were systematically characterized using three correlated theoretical techniques: density functional theory using the B3LYP functional, spinrestricted second-order perturbation theory, and singles + doubles coupled cluster theory with perturbative triples. On the basis of thermodynamic data, the existence of these ions in inductively coupled plasma mass spectrometry (ICP-MS) experiments is not surprising since the ions are predicted to be considerably more stable than their corresponding dissociation products (by 30−170 kcal/mol). While each pair of isoelectronic ions exhibit very similar thermodynamic and kinetic characteristics, there are significant differences within each series. While the mechanism for dissociation of the larger ions occurs through hydrogen abstraction, the triatomic ions (HCO+ and HN2+) appear to dissociate by proton abstraction. These differing mechanisms help to explain large differences in the abundances of HN2+ and HCO+ observed in ICP-MS experiments. Disciplines Chemistry CommentsReprinted (adapted) ReceiVed: September 7, 2007; In Final Form: January 4, 2008 Two series of small polyatomic ions, H x CO + and H x N 2 + (x ) 1, 2, 3), were systematically characterized using three correlated theoretical techniques: density functional theory using the B3LYP functional, spinrestricted second-order perturbation theory, and singles + doubles coupled cluster theory with perturbative triples. On the basis of thermodynamic data, the existence of these ions in inductively coupled plasma mass spectrometry (ICP-MS) experiments is not surprising since the ions are predicted to be considerably more stable than their corresponding dissociation products (by 30-170 kcal/mol). While each pair of isoelectronic ions exhibit very similar thermodynamic and kinetic characteristics, there are significant differences within each series. While the mechanism for dissociation of the larger ions occurs through hydrogen abstraction, the triatomic ions (HCO + and HN 2 + ) appear to dissociate by proton abstraction. These differing mechanisms help to explain large differences in the abundances of HN 2 + and HCO + observed in ICP-MS experiments.

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Section: Introductionmentioning

confidence: 99%

Theoretical Investigation of Small Polyatomic Ions Observed in Inductively Coupled Plasma Mass Spectrometry: H_xCO⁺ and H_xN₂⁺ (x = 1, 2, 3)

et al. 2008

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“…Vaporization, atomization, and ionization of the sample aerosol in the ICP depend on the physical properties of the plasma, namely the gas kinetic temperature (T gas ), electron number density (n e ) and electron temperature (T e ) [18,19]. Especially T gas is considered to be the dominating parameter for vaporization and atomization of the aerosol particles.…”

mentioning

confidence: 99%

“…Important for the atomization of the aerosol and the dissociation of molecular ions is mainly the temperature in the central channel of the ICP and finally directly in front of the sampler cone orifice [18]. The situation is more complex when helium is used as carrier gas and added to the argon in the central channel of the ICP.…”

mentioning

confidence: 99%

“…For non-fractionating vaporization and atomization, this intensity ratio should reflect the molar concentration ratio in the ablated material because of the similar ionization energy and close m/z values. The results are compared to the ThO ϩ /Th ϩ ratio, which can be used as an estimate of T gas [18,34], and the response curves obtained under different operation conditions, which can serve as an estimate for the effect of the ICP operation conditions on the kinetic energy of ions with different m/z and the resulting mass bias of the ICPMS.…”

mentioning

confidence: 99%

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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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“…The dissociation energy of C ϩ Ϫ H is 4.08 eV [27]. These values are comparable to those of other polyatomic ions seen from the ICP [28,29], and theoretical calculations of the abundance ratio indicates some 12 C 1 H ϩ could survive in the plasma [25]. The variation of the observed ratios for the different compounds suggests that the 12 C 1 H ϩ interference was worst for myoglobin, moderate for glucose, and minimal for tryptophan [25].…”

Section: Plasma Optimization and Removal Of 12 C 1 H ϩmentioning

confidence: 53%

Determination of carbon isotope ratios in amino acids, proteins, and oligosaccharides by inductively coupled plasma-mass spectrometry

Luong

Houk

2003

J. Am. Soc. Mass Spectrom.

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Carbon isotope ratios ( 12 C/ 13 C) are measured for aqueous solutions of tryptophan, myoglobin, and ␤-cyclodextrin using C ϩ ions from an inductively coupled plasma (ICP) and a prototype twin quadrupole mass spectrometer (MS). 13 C/ 12 C ratios can be determined with a relative standard deviation (RSD) of ϳ1%. This precision is close to the limiting value predicted by counting statistics (1.16%). Spectral interference on 13 C ϩ , presumably from 12 C 1 H ϩ , comes from the incomplete dissociation of myoglobin and/or ␤-cyclodextrin, but not tryptophan. Decreasing the aerosol gas flow rate slightly from that which yields maximum signal eliminates this 12 C 1 H ϩ interference. The count rate of the minor isotope ( 13 C ϩ ) can be artificially enhanced by increasing the voltage of the 13 C ϩ detector, and/or by shifting the ion beam splitter offset from the central axis. Instrumental modifications to the MS that improve the sensitivity are also described. I nductively coupled plasma mass spectrometry (ICP-MS) is a versatile technique for elemental and isotopic analysis. Applications of ICP-MS range from elemental determinations to isotopic analysis in nutrition, clinical studies, geochemistry, environmental studies, and the semiconductor and nuclear industries. ICP-MS has long linear dynamic range (eight orders of magnitude) and detection limits at part per trillion levels for many elements. Most ICP-MS instruments contain a quadrupole or magnetic sector mass spectrometer with a single detector. These are sequential devices that do not measure the various m/z values of interest at precisely the same time. They provide moderate to good precision in isotope ratio measurements, typically 0.05% relative standard deviation (RSD) on ratios close to unity, with substantially poorer precision on large or small ratios [1][2][3][4].Much of the instability in the ion signal is caused by flicker noise from the ICP. This source of noise can be eliminated by measuring the various m/z values at the same time using a multicollector magnetic sector device [5,6]. We have described a unique instrument with two quadrupole mass filters and an ion beam splitter that also eliminates the flicker noise contribution to isotope ratios [7]. Allen and co-workers have analyzed solid copper and steel samples using laser ablation with this twin quadrupole device. The isotope ratio precision reported by Allen et al. was 0.06 to 0.1% for 52 Cr/ 53 Cr, depending on the dwell time and averaging method used [8].This paper evaluates the performance obtained for measurement of carbon isotope ratios from organic compounds at natural isotopic abundance. The ultimate goal is to provide a method for carbon isotopic analyses in bioorganic molecules in aqueous solution. This is an ambitious goal, since carbon is only 1 to 5% ionized in the ICP [9]. Thus, the sensitivity (i.e., count rate per unit concentration) is much lower than that for the metals and metalloids usually determined by ICP-MS, and 13 C is only ϳ1% of 12 C. No more than 0.1% of the analyte ion...

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Dissociation of polyatomic ions in the inductively coupled plasma

Cited by 71 publications

References 62 publications

Theoretical Investigation of Small Polyatomic Ions Observed in Inductively Coupled Plasma Mass Spectrometry: H_xCO⁺ and H_xN₂⁺ (x = 1, 2, 3)

Theoretical Investigation of Small Polyatomic Ions Observed in Inductively Coupled Plasma Mass Spectrometry: H_xCO⁺ and H_xN₂⁺ (x = 1, 2, 3)

Analyte response in laser ablation inductively coupled plasma mass spectrometry

Determination of carbon isotope ratios in amino acids, proteins, and oligosaccharides by inductively coupled plasma-mass spectrometry

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Dissociation of polyatomic ions in the inductively coupled plasma

Cited by 71 publications

References 62 publications

Theoretical Investigation of Small Polyatomic Ions Observed in Inductively Coupled Plasma Mass Spectrometry: HxCO+ and HxN2+ (x = 1, 2, 3)

Theoretical Investigation of Small Polyatomic Ions Observed in Inductively Coupled Plasma Mass Spectrometry: HxCO+ and HxN2+ (x = 1, 2, 3)

Analyte response in laser ablation inductively coupled plasma mass spectrometry

Determination of carbon isotope ratios in amino acids, proteins, and oligosaccharides by inductively coupled plasma-mass spectrometry

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Product

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Theoretical Investigation of Small Polyatomic Ions Observed in Inductively Coupled Plasma Mass Spectrometry: H_xCO⁺ and H_xN₂⁺ (x = 1, 2, 3)

Theoretical Investigation of Small Polyatomic Ions Observed in Inductively Coupled Plasma Mass Spectrometry: H_xCO⁺ and H_xN₂⁺ (x = 1, 2, 3)