A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:
Metal Argide (MAr+) Ions are lost during ion extraction in laser ablation-inductively coupled plasma-mass spectrometry
09 March 2012, 11:53:49
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Travis M. Witte, R.S. Houk
The abundance of metal argide (MAr+) ions during laser ablation- inductively coupled plasma-mass spectrometry (LA-ICP-MS) is measured during ablation of pure samples of transition metals. As expected, the relative abundance of MAr+ ions to M+ ions for various elements increases as the dissociation energy (D0) of the ion increases. Gas kinetic temperatures (Tgas) are determined from the calculated MAr+/M+ ratios and are used to indicate the origins of MAr+ ions. The determined Tgas values are very high, 8000K to ≥20,000K, which indicate that MAr+ ions are much less abundant in the mass spectrum than expected based upon plasma conditions. Collision-induced dissociation (CID) during the ion extraction process is suggested to be responsible for removal of MAr+ ions. Factors responsible for these collisions are discussed.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Travis M. Witte, R.S. Houk
The abundance of metal argide (MAr+) ions during laser ablation- inductively coupled plasma-mass spectrometry (LA-ICP-MS) is measured during ablation of pure samples of transition metals. As expected, the relative abundance of MAr+ ions to M+ ions for various elements increases as the dissociation energy (D0) of the ion increases. Gas kinetic temperatures (Tgas) are determined from the calculated MAr+/M+ ratios and are used to indicate the origins of MAr+ ions. The determined Tgas values are very high, 8000K to ≥20,000K, which indicate that MAr+ ions are much less abundant in the mass spectrum than expected based upon plasma conditions. Collision-induced dissociation (CID) during the ion extraction process is suggested to be responsible for removal of MAr+ ions. Factors responsible for these collisions are discussed.
A compact and low cost laser induced breakdown spectroscopic system: Application for simultaneous determination of chromium and nickel in steel using multivariate calibration
09 March 2012, 11:53:49
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Fabiano Barbieri Gonzaga, Celio Pasquini
This work describes a compact and low cost analyzer for laser induced breakdown spectroscopy (LIBS) based on a diode pumped passively Q-switched Nd:LSB microchip laser and a conventional Czerny-Turner spectrograph (spectral range from about 250 to 390nm) containing a non-intensified, non-gated and non-cooled 1024 pixel linear sensor array. The new LIBS instrument was applied for analyzing steel samples containing chromium and nickel in the concentration range from about 5 to 26% w/w (certified reference materials), integrating the emitted radiation for 40s under continuous application of laser pulses at 2kHz for each acquired spectrum (integration of about 80,000 plasmas). The emission data from about 356 to 362nm and 340 to 354nm were employed for the construction of two Partial Least Squares (PLS) calibration models for determination of chromium and nickel, respectively. The average relative errors of prediction of chromium and nickel concentrations were 3.7 and 6.7%, respectively, which are similar to or lower than those obtained using higher cost LIBS analyzers. The results have shown that multivariate calibration can help to overcome the decreasing instrumental performance associated with the low cost equipment.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Fabiano Barbieri Gonzaga, Celio Pasquini
This work describes a compact and low cost analyzer for laser induced breakdown spectroscopy (LIBS) based on a diode pumped passively Q-switched Nd:LSB microchip laser and a conventional Czerny-Turner spectrograph (spectral range from about 250 to 390nm) containing a non-intensified, non-gated and non-cooled 1024 pixel linear sensor array. The new LIBS instrument was applied for analyzing steel samples containing chromium and nickel in the concentration range from about 5 to 26% w/w (certified reference materials), integrating the emitted radiation for 40s under continuous application of laser pulses at 2kHz for each acquired spectrum (integration of about 80,000 plasmas). The emission data from about 356 to 362nm and 340 to 354nm were employed for the construction of two Partial Least Squares (PLS) calibration models for determination of chromium and nickel, respectively. The average relative errors of prediction of chromium and nickel concentrations were 3.7 and 6.7%, respectively, which are similar to or lower than those obtained using higher cost LIBS analyzers. The results have shown that multivariate calibration can help to overcome the decreasing instrumental performance associated with the low cost equipment.
Application of the wavelength dispersive X-ray fluorescence technique to determine soil fluorine with consideration of iron content in the matrix
09 March 2012, 11:53:49
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jinsung An, Ki-Hyun Kim, Hye-On Yoon, Jungju Seo
The suitability of the wavelength dispersive X-ray fluorescence (WD-XRF) technique for the quantitative analysis of fluorine in soil was assessed in this study. Fluorine standards for WD-XRF calibration with soil matrices consisting of SiO2, Al2O3, Fe2O3, and CaO were prepared by varying the concentrations of CaF2 as a source of fluorine. Based on the standard calibration, the limits of detection and quantification were calculated as 812 and 2690mg-F/kg-solid (or 1.62 and 5.39mg-F in absolute mass term), respectively. In addition, the fluorine intensities of the standard samples with high iron content increased significantly compared to those with low iron content. Because of proximity between F-Kα line and Fe-Lα line, the higher iron content preferably helped increase background fluorine intensities. As a means to compensate for the iron interference effect in fluorine analysis, the correction factor (CF) (0.0045) was derived based on the slope ratios between the measured X-ray intensity at the Bragg angle of 43.174° and iron content in the standard sample. The soil fluorine concentration determined by WD-XRF after the CF adjustment exhibited a significantly high correlation with that of the classical alkali fusion-ISE analysis. These findings clearly demonstrated that the WD-XRF technique is reliable enough to allow an easy, precise, and rapid quantitative determination of fluorine in a solid sample (such as iron-bound soil) compared to conventional methods.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jinsung An, Ki-Hyun Kim, Hye-On Yoon, Jungju Seo
The suitability of the wavelength dispersive X-ray fluorescence (WD-XRF) technique for the quantitative analysis of fluorine in soil was assessed in this study. Fluorine standards for WD-XRF calibration with soil matrices consisting of SiO2, Al2O3, Fe2O3, and CaO were prepared by varying the concentrations of CaF2 as a source of fluorine. Based on the standard calibration, the limits of detection and quantification were calculated as 812 and 2690mg-F/kg-solid (or 1.62 and 5.39mg-F in absolute mass term), respectively. In addition, the fluorine intensities of the standard samples with high iron content increased significantly compared to those with low iron content. Because of proximity between F-Kα line and Fe-Lα line, the higher iron content preferably helped increase background fluorine intensities. As a means to compensate for the iron interference effect in fluorine analysis, the correction factor (CF) (0.0045) was derived based on the slope ratios between the measured X-ray intensity at the Bragg angle of 43.174° and iron content in the standard sample. The soil fluorine concentration determined by WD-XRF after the CF adjustment exhibited a significantly high correlation with that of the classical alkali fusion-ISE analysis. These findings clearly demonstrated that the WD-XRF technique is reliable enough to allow an easy, precise, and rapid quantitative determination of fluorine in a solid sample (such as iron-bound soil) compared to conventional methods.
Origins of Polyatomic Ions in Laser Ablation - Inductively Coupled Plasma – Mass Spectrometry: An Examination of Metal Oxide Ions & Effects of Nitrogen and Helium in the Aerosol Gas Flow
09 March 2012, 11:53:49
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Travis M. Witte, R.S. Houk
Differences in the origins of polyatomic ions in wet plasma conditions, as exist in solution inductively coupled plasma-mass spectrometry (ICP-MS), versus dry plasma conditions, found in laser ablation (LA)-ICP-MS, are investigated. Silicate and metal samples are ablated and gas kinetic temperature (Tgas) is measured to establish the origins of metal oxide (MO+) ions. MO+ ion abundances observed from both the ablation of silicate samples and metallic samples are found to correspond to formation of the polyatomic ion in the ICP. The same strategy is applied to oxide ratios measured when additional gases (N2 and He) are introduced into the aerosol gas flow. N2 is found to decrease the MO+/M+ signal ratio by maximizing atomic sensitivity at lower total gas loads. The addition of He reduces polyatomic ions throughout the plasma. Use of both N2 and He produces the lowest MO+/M+ signal ratio and highest Tgas values at the position sampled in the ICP. By gaining a better understanding of the origin of polyatomic ions in LA-ICP-MS and their behavior in mixed gas plasmas, perhaps strategies can be developed to minimize polyatomic interferences in the mass spectrum.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Travis M. Witte, R.S. Houk
Differences in the origins of polyatomic ions in wet plasma conditions, as exist in solution inductively coupled plasma-mass spectrometry (ICP-MS), versus dry plasma conditions, found in laser ablation (LA)-ICP-MS, are investigated. Silicate and metal samples are ablated and gas kinetic temperature (Tgas) is measured to establish the origins of metal oxide (MO+) ions. MO+ ion abundances observed from both the ablation of silicate samples and metallic samples are found to correspond to formation of the polyatomic ion in the ICP. The same strategy is applied to oxide ratios measured when additional gases (N2 and He) are introduced into the aerosol gas flow. N2 is found to decrease the MO+/M+ signal ratio by maximizing atomic sensitivity at lower total gas loads. The addition of He reduces polyatomic ions throughout the plasma. Use of both N2 and He produces the lowest MO+/M+ signal ratio and highest Tgas values at the position sampled in the ICP. By gaining a better understanding of the origin of polyatomic ions in LA-ICP-MS and their behavior in mixed gas plasmas, perhaps strategies can be developed to minimize polyatomic interferences in the mass spectrum.
Quantification of the fluorine containing drug 5-fluorouracil in cancer cells by GaF molecular absorption via high-resolution continuum source molecular absorption spectrometry
09 March 2012, 11:53:49
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Magnus Krüger, Mao-Dong Huang, Helmut Becker-Roß, Stefan Florek, Ingo Ott, Ronald Gust
The development of high-resolution continuum source molecular absorption spectrometry made the quantification of fluorine feasible by measuring the molecular absorption as gallium monofluoride (GaF). Using this new technique, we developed on the example of 5-fluorouracil (5-FU) a graphite furnace method to quantify fluorine in organic molecules. The effect of 5-FU on the generation of the diatomic GaF molecule was investigated. The experimental conditions such as gallium nitrate amount, temperature program, interfering anions (represented as corresponding acids) and calibration for the determination of 5-FU in standard solution and in cellular matrix samples were investigated and optimized. The sample matrix showed no effect on the sensitivity of GaF molecular absorption. A simple calibration curve using an inorganic sodium fluoride solution can conveniently be used for the calibration. The described method is sensitive and the achievable limit of detection is 0.23ng of 5-FU. In order to establish the concept of “fluorine as a probe in medicinal chemistry” an exemplary application was selected, in which the developed method was successfully demonstrated by performing cellular uptake studies of the 5-FU in human colon carcinoma cells.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Magnus Krüger, Mao-Dong Huang, Helmut Becker-Roß, Stefan Florek, Ingo Ott, Ronald Gust
The development of high-resolution continuum source molecular absorption spectrometry made the quantification of fluorine feasible by measuring the molecular absorption as gallium monofluoride (GaF). Using this new technique, we developed on the example of 5-fluorouracil (5-FU) a graphite furnace method to quantify fluorine in organic molecules. The effect of 5-FU on the generation of the diatomic GaF molecule was investigated. The experimental conditions such as gallium nitrate amount, temperature program, interfering anions (represented as corresponding acids) and calibration for the determination of 5-FU in standard solution and in cellular matrix samples were investigated and optimized. The sample matrix showed no effect on the sensitivity of GaF molecular absorption. A simple calibration curve using an inorganic sodium fluoride solution can conveniently be used for the calibration. The described method is sensitive and the achievable limit of detection is 0.23ng of 5-FU. In order to establish the concept of “fluorine as a probe in medicinal chemistry” an exemplary application was selected, in which the developed method was successfully demonstrated by performing cellular uptake studies of the 5-FU in human colon carcinoma cells.
Experimental characterization of the effect of skimmer cone design on shock formation and ion transmission efficiency in the vacuum interface of an inductively coupled plasma mass spectrometer
09 March 2012, 11:53:49
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Nicholas Taylor, Paul B. Farnsworth
Laser-induced fluorescence has been used to evaluate five commercially available skimmer cone designs from inductively coupled plasma mass spectrometers in terms of shock formation at the skimmer tip and transmission efficiency. Efficiency was measured as the ratio of analyte density downstream from the skimmer tip to analyte density upstream from the skimmer tip. The strongest shock was recorded for a skimmer with a cylindrical throat, and the weakest shock was produced by the skimmer with the largest diameter and a conical throat. Transmission efficiency increased with increasing orifice diameter. Coulombic effects, revealed in a comparison between the behaviors of neutral barium atoms and barium ions, were small. Transmission efficiencies recorded for calcium ions were lower than those recorded for barium ions by more than a factor of two.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Nicholas Taylor, Paul B. Farnsworth
Laser-induced fluorescence has been used to evaluate five commercially available skimmer cone designs from inductively coupled plasma mass spectrometers in terms of shock formation at the skimmer tip and transmission efficiency. Efficiency was measured as the ratio of analyte density downstream from the skimmer tip to analyte density upstream from the skimmer tip. The strongest shock was recorded for a skimmer with a cylindrical throat, and the weakest shock was produced by the skimmer with the largest diameter and a conical throat. Transmission efficiency increased with increasing orifice diameter. Coulombic effects, revealed in a comparison between the behaviors of neutral barium atoms and barium ions, were small. Transmission efficiencies recorded for calcium ions were lower than those recorded for barium ions by more than a factor of two.
Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report) [©2011 IUPAC]
09 March 2012, 11:53:49
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Alessandro D'Ulivo
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Alessandro D'Ulivo
A simplified calculation of power-broadened linewidths, with application to resonance ionization mass spectrometry
09 March 2012, 11:53:49
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jonathan Levine
I present a simple derivation of the power-broadened linewidth of an optical transition in a two-level atom. The novelty of the approach lies in its flexibility, as the approach described here can be applied to any spectral lineshape, corresponding to either homogeneous or inhomogeneous broadening mechanisms. For a Lorentzian profile, I recover the same dependence of linewidth on laser power that one calculates from the optical Bloch equations. The present treatment makes explicit that power broadening arises because of the saturability of the atomic response to intense lasers, rather than to explicitly quantum mechanical aspects of the laser–atom interaction, all of which are ignored. I discuss the utility of power broadening in resonance ionization mass spectrometry, where it is an important means of mitigating unwanted instrumental isotope fractionation.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jonathan Levine
I present a simple derivation of the power-broadened linewidth of an optical transition in a two-level atom. The novelty of the approach lies in its flexibility, as the approach described here can be applied to any spectral lineshape, corresponding to either homogeneous or inhomogeneous broadening mechanisms. For a Lorentzian profile, I recover the same dependence of linewidth on laser power that one calculates from the optical Bloch equations. The present treatment makes explicit that power broadening arises because of the saturability of the atomic response to intense lasers, rather than to explicitly quantum mechanical aspects of the laser–atom interaction, all of which are ignored. I discuss the utility of power broadening in resonance ionization mass spectrometry, where it is an important means of mitigating unwanted instrumental isotope fractionation.
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