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Micro- and nano-volume samples by electrothermal, near-torch vaporization sample introduction using removable, interchangeable and portable rhenium coiled-filament assemblies and axially-viewed inductively coupled plasma-atomic emission spectrometry
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Hamid R. Badiei, Bryant Lai, Vassili Karanassios
An electrothermal, near-torch vaporization (NTV) sample introduction for micro- or nano-volume samples is described. Samples were pipetted onto coiled-filament assemblies that were purposely developed to be removable and interchangeable and were dried and vaporized into a small-volume vaporization chamber that clips onto any ICP torch with a ball joint. Interchangeable assemblies were also constructed to be small-size (e.g., less than 3cm long with max diameter of 0.65cm) and light-weight (1.4g) so that they can be portable. Interchangeable assemblies with volume-capacities in three ranges (i.e., <1 μL, 1–10 μL and 10–100 μL) were fabricated and used. The horizontally-operated NTV sample introduction was interfaced to an axially-viewed ICP-AES (inductively coupled plasma-atomic emission spectrometry) system and NTV was optimized using ICP-AES and 8 elements (Pb, Cd, Zn, V, Ba, Mg, Be and Ca). Precision was 1.0-2.3% (peak height) and 1.1-2.4% (peak area). Detection limits (obtained using 5 μL volumes) expressed in absolute-amounts ranged between 4pg for Pb to 0.3fg (~5 million atoms) for Ca. Detection limits expressed in concentration units (obtained using 100 μL volumes of diluted, single-element standard solutions) were: 50pg/mL for Pb; 10pg/mL for Cd; 9pg/mL for Zn; 1pg/mL for V; 0.9pg/mL for Ba; 0.5pg/mL for Mg; 50fg/mL for Be; and 3fg/mL for Ca. Analytical capability and utility was demonstrated using the determination of Pb in pg/mL levels of diluted natural water Certified Reference Material (CRM) and the determination of Zn in 80nL volumes of the liquid extracted from an individual vesicle. It is shown that portable and interchangeable assemblies with dried sample residues on them can be transported without analyte loss (for the concentrations tested), thus opening up the possibility for “taking part of the lab to the sample” applications, such as testing for Cu concentration-compliance with the lead-copper rule of the Environmental Protection Agency. It is also shown that interchangeable assemblies with volume-capacities in the ranges mentioned above can be used interchangeably in the same calibration curve, thus in some cases and for on-site applications, volume-of-sample can be substituted for sample-dilution.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Hamid R. Badiei, Bryant Lai, Vassili Karanassios
An electrothermal, near-torch vaporization (NTV) sample introduction for micro- or nano-volume samples is described. Samples were pipetted onto coiled-filament assemblies that were purposely developed to be removable and interchangeable and were dried and vaporized into a small-volume vaporization chamber that clips onto any ICP torch with a ball joint. Interchangeable assemblies were also constructed to be small-size (e.g., less than 3cm long with max diameter of 0.65cm) and light-weight (1.4g) so that they can be portable. Interchangeable assemblies with volume-capacities in three ranges (i.e., <1 μL, 1–10 μL and 10–100 μL) were fabricated and used. The horizontally-operated NTV sample introduction was interfaced to an axially-viewed ICP-AES (inductively coupled plasma-atomic emission spectrometry) system and NTV was optimized using ICP-AES and 8 elements (Pb, Cd, Zn, V, Ba, Mg, Be and Ca). Precision was 1.0-2.3% (peak height) and 1.1-2.4% (peak area). Detection limits (obtained using 5 μL volumes) expressed in absolute-amounts ranged between 4pg for Pb to 0.3fg (~5 million atoms) for Ca. Detection limits expressed in concentration units (obtained using 100 μL volumes of diluted, single-element standard solutions) were: 50pg/mL for Pb; 10pg/mL for Cd; 9pg/mL for Zn; 1pg/mL for V; 0.9pg/mL for Ba; 0.5pg/mL for Mg; 50fg/mL for Be; and 3fg/mL for Ca. Analytical capability and utility was demonstrated using the determination of Pb in pg/mL levels of diluted natural water Certified Reference Material (CRM) and the determination of Zn in 80nL volumes of the liquid extracted from an individual vesicle. It is shown that portable and interchangeable assemblies with dried sample residues on them can be transported without analyte loss (for the concentrations tested), thus opening up the possibility for “taking part of the lab to the sample” applications, such as testing for Cu concentration-compliance with the lead-copper rule of the Environmental Protection Agency. It is also shown that interchangeable assemblies with volume-capacities in the ranges mentioned above can be used interchangeably in the same calibration curve, thus in some cases and for on-site applications, volume-of-sample can be substituted for sample-dilution.
Highlights
► Absolute detection limits from 4pg (Pb) to 0.3fg (~5 million atoms) for Ca ► Relative detection limits (100 μL) from 50pg/mL for Pb to 3fg/mL for Ca ► Pb was determined in the 100's of pg/mL level using 100 μL of diluted CRM ► Zn in individual vesicles was determined using 80nL-volume samples ► Analytes pipetted on coils on-site and concentration determined in the labFocusing systems for the generation of X-ray micro beam: An overview
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
A. Guilherme, G. Buzanich, M.L. Carvalho
This manuscript reviews the most used optical systems for X-ray microprobes and summarizes the experiences in research with synchrotron radiation as well as with X-ray tube generators. The need for smaller beam spot sizes for various applications and the unique properties of X-rays have induced a remarkable and fast development in X-ray optical systems. These systems are divided into three main categories: diffractive, reflective and refractive. Examples of the three will be covered in this paper, highlighting the properties that allow having spot sizes down to sub-micrometer regime. However, the extraordinary capabilities of such systems are always relative. Therefore, an overview of the techniques that use such optical systems will be given, emphasizing their applicability on several case studies.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
A. Guilherme, G. Buzanich, M.L. Carvalho
This manuscript reviews the most used optical systems for X-ray microprobes and summarizes the experiences in research with synchrotron radiation as well as with X-ray tube generators. The need for smaller beam spot sizes for various applications and the unique properties of X-rays have induced a remarkable and fast development in X-ray optical systems. These systems are divided into three main categories: diffractive, reflective and refractive. Examples of the three will be covered in this paper, highlighting the properties that allow having spot sizes down to sub-micrometer regime. However, the extraordinary capabilities of such systems are always relative. Therefore, an overview of the techniques that use such optical systems will be given, emphasizing their applicability on several case studies.
Highlights
► This work makes a revision on the most used focusing systems for X-ray microprobes ► This work summarizes the experiences with synchrotron radiation ► This work summarizes the experiences with X-ray tube generators. ► This work gives examples for diffractive, reflective and refractive systemsTesting a portable laser-induced breakdown spectroscopy system on geological samples
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jozef Rakovský, Olivier Musset, JeanFrançois Buoncristiani, Vincent Bichet, Fabrice Monna, Pascal Neige, Pavel Veis
This paper illustrates the potentialities of a home-made portable LIBS (laser-induced breakdown spectroscopy) instrument in Earth sciences, more particularly in geochemically recognizing (i) tephra layers in lacustrine sediments and (ii) fossilization processes in ammonites. Abundances for selected lines of Al, Ca, Fe, Ti, Ba and Na were determined in lacustrine chalk sediments of the Jura, where the Laacher See Tephra (LST) layer is recorded. A statistical treatment of elemental maps produced from the section of a sedimentary column containing the LST event allows instrumental conditions to be optimized. Accumulating spectra from close shot positions gives better results than multiplying shots at the same location. A depth profile method was applied to study ammonite fossilization (pyritization, phosphatization) processes. Depth variations of Fe, Ca, Al intensities, and Fe/Ca and Al/Ca ratios provide indications about pyritization, but phosphatization processes cannot be determined with our device.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jozef Rakovský, Olivier Musset, JeanFrançois Buoncristiani, Vincent Bichet, Fabrice Monna, Pascal Neige, Pavel Veis
This paper illustrates the potentialities of a home-made portable LIBS (laser-induced breakdown spectroscopy) instrument in Earth sciences, more particularly in geochemically recognizing (i) tephra layers in lacustrine sediments and (ii) fossilization processes in ammonites. Abundances for selected lines of Al, Ca, Fe, Ti, Ba and Na were determined in lacustrine chalk sediments of the Jura, where the Laacher See Tephra (LST) layer is recorded. A statistical treatment of elemental maps produced from the section of a sedimentary column containing the LST event allows instrumental conditions to be optimized. Accumulating spectra from close shot positions gives better results than multiplying shots at the same location. A depth profile method was applied to study ammonite fossilization (pyritization, phosphatization) processes. Depth variations of Fe, Ca, Al intensities, and Fe/Ca and Al/Ca ratios provide indications about pyritization, but phosphatization processes cannot be determined with our device.
Highlights
► Element cartography maps for sediment which contains tephra layer have been created. ► The maps have been used for on-site conditions determination by statistical treatment. ► Pyritization process on ammonite surface was identified successfully.An investigation of Laser Induced Breakdown Spectroscopy for use as a control in the laser removal of rock from fossils found at the Malapa hominin site, South Africa
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
D.E. Roberts, A. du Plessis, J. Steyn, L.R. Botha, S. Pityana, L.R. Berger
Laser Induced Breakdown Spectroscopy (LIBS) was used to study the spectra from fossils and surrounding rock recovered from the Cradle of Mankind site at Malapa, South Africa. The objective was to find a suitable spectral line(s), specific to fossils, which could be used as a control signal to limit damage to fossils during high speed laser removal of the encasing rock. The calcified clastic matrix (rock) encasing the fossils was found to emit a variety of complex LIBS spectra. Nevertheless, it was found possible to distinguish fossils in a single LIBS pulse, and without significant damage to the fossil, using spectral lines of neutral phosphorus.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
D.E. Roberts, A. du Plessis, J. Steyn, L.R. Botha, S. Pityana, L.R. Berger
Laser Induced Breakdown Spectroscopy (LIBS) was used to study the spectra from fossils and surrounding rock recovered from the Cradle of Mankind site at Malapa, South Africa. The objective was to find a suitable spectral line(s), specific to fossils, which could be used as a control signal to limit damage to fossils during high speed laser removal of the encasing rock. The calcified clastic matrix (rock) encasing the fossils was found to emit a variety of complex LIBS spectra. Nevertheless, it was found possible to distinguish fossils in a single LIBS pulse, and without significant damage to the fossil, using spectral lines of neutral phosphorus.
Highlights
► LIBS used to discriminate fossils from rock as potential processing control mechanism. ► 2million year old fossils from Malapa hominin site found to be high in phosphorus. ► Rock spectral lines from silicon, iron and manganese, but no phosphorus. ► Holds great promise for process control in laser preparation of fossils. ► Also promising for accurate identification of fossils at excavation sites.Evaluation of quartz tubes as atomization cells for gold determination by thermospray flame furnace atomic absorption spectrometry
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Ezequiel Morzan, Ornela Piano, Jorge Stripeikis, Mabel Tudino
This work describes the development of a new analytical procedure able to determine gold by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) using nickel tubes (NiT) and quartz tubes (QT) as atomization cells. Experiments involving changes in the flow injection operational parameters, reagents concentrations and sizes of the QT were performed in order to optimize sensitivity. Under the same operational conditions, it was observed that the employment of QT increases the sensitivity of gold determination when compared to the nickel tube. Since solutions of highly concentrated hydrochloric acid showed the best performance as carriers, quartz tubes were also preferred due to its greater tolerance to corrosion by mineral acids in comparison to NiT. In addition, changes in the internal diameter of the QT revealed an important improvement in sensitivity for smaller tubes. Under optimized conditions the main figures of merit showed values close to that of graphite furnace atomic absorption spectrometry with the addition of an excellent improvement of the sample throughput. They are: LOD (3s): 0.004μgmL-1, sensitivity: 0.306 (μgmL-1)-1, RSD% (n=10, 1μgmL-1): 2.5, linear range: 0.01 - 4μgmL-1 and sample throughput: 72h-1. This new method was employed for the determination of gold in homeopathic medicines with no need of sample digestion. Validation of the analytical results will be shown. A fully discussion of the most relevant findings regarding the role of the atomization cell as an strategic key for improving sensitivity will be also provided.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Ezequiel Morzan, Ornela Piano, Jorge Stripeikis, Mabel Tudino
This work describes the development of a new analytical procedure able to determine gold by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) using nickel tubes (NiT) and quartz tubes (QT) as atomization cells. Experiments involving changes in the flow injection operational parameters, reagents concentrations and sizes of the QT were performed in order to optimize sensitivity. Under the same operational conditions, it was observed that the employment of QT increases the sensitivity of gold determination when compared to the nickel tube. Since solutions of highly concentrated hydrochloric acid showed the best performance as carriers, quartz tubes were also preferred due to its greater tolerance to corrosion by mineral acids in comparison to NiT. In addition, changes in the internal diameter of the QT revealed an important improvement in sensitivity for smaller tubes. Under optimized conditions the main figures of merit showed values close to that of graphite furnace atomic absorption spectrometry with the addition of an excellent improvement of the sample throughput. They are: LOD (3s): 0.004μgmL-1, sensitivity: 0.306 (μgmL-1)-1, RSD% (n=10, 1μgmL-1): 2.5, linear range: 0.01 - 4μgmL-1 and sample throughput: 72h-1. This new method was employed for the determination of gold in homeopathic medicines with no need of sample digestion. Validation of the analytical results will be shown. A fully discussion of the most relevant findings regarding the role of the atomization cell as an strategic key for improving sensitivity will be also provided.
Highlights
► Quartz tubes as furnaces in TS-FFAAS ► Small tubes for controlling radial dispersion ► Improved figures of merit for gold determination ► Analysis of homeopathic medicinesPreface
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Şerife Yalcin, Roberta Fantoni
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Şerife Yalcin, Roberta Fantoni
Calibration analysis of zeolites by laser induced breakdown spectroscopy
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
M. Horňáčková, Z. Grolmusová, M. Horňáček, J. Rakovský, P. Hudec, P. Veis
Laser induced breakdown spectroscopy was used for calibration analysis of different types of microporous crystalline aluminosilicates with exactly ordered structure — zeolites. The LIBS plasma was generated using a Q-switched Nd:YAG laser operating at the wavelength of 532nm and providing laser pulses of 4ns duration. Plasma emission was analysed by echelle type emission spectrometer, providing wide spectral range 200–950nm. The spectrometer was equipped with intensified CCD camera providing rapid spectral acquisition (gating time from 5ns). The optimum experimental conditions (time delay, gate width and laser pulse energy) have been determined for reliable use of LIBS for quantitative analysis. Samples of different molar ratios of Si/Al were used to create the calibration curves. Calibration curves for different types of zeolites (mordenite, type Y and ZSM-5) were constructed. Molar ratios of Si/Al for samples used for calibration were determined by classical wet chemical analysis and were in the range 5.3–51.8 for mordenite, 2.3–12.8 for type Y and 14–600 for ZSM-5. Zeolites with these molar ratios of Si/Al are usually used as catalysts in alkylation reactions. Laser induced breakdown spectroscopy is a suitable method for analysis of molar ratio Si/Al in zeolites, because it is simple, fast, and does not require sample preparation compared with classical wet chemical analysis which are time consuming, require difficult sample preparation and manipulation with strong acids and bases.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
M. Horňáčková, Z. Grolmusová, M. Horňáček, J. Rakovský, P. Hudec, P. Veis
Laser induced breakdown spectroscopy was used for calibration analysis of different types of microporous crystalline aluminosilicates with exactly ordered structure — zeolites. The LIBS plasma was generated using a Q-switched Nd:YAG laser operating at the wavelength of 532nm and providing laser pulses of 4ns duration. Plasma emission was analysed by echelle type emission spectrometer, providing wide spectral range 200–950nm. The spectrometer was equipped with intensified CCD camera providing rapid spectral acquisition (gating time from 5ns). The optimum experimental conditions (time delay, gate width and laser pulse energy) have been determined for reliable use of LIBS for quantitative analysis. Samples of different molar ratios of Si/Al were used to create the calibration curves. Calibration curves for different types of zeolites (mordenite, type Y and ZSM-5) were constructed. Molar ratios of Si/Al for samples used for calibration were determined by classical wet chemical analysis and were in the range 5.3–51.8 for mordenite, 2.3–12.8 for type Y and 14–600 for ZSM-5. Zeolites with these molar ratios of Si/Al are usually used as catalysts in alkylation reactions. Laser induced breakdown spectroscopy is a suitable method for analysis of molar ratio Si/Al in zeolites, because it is simple, fast, and does not require sample preparation compared with classical wet chemical analysis which are time consuming, require difficult sample preparation and manipulation with strong acids and bases.
Highlights
► Determination of optimal experimental conditions for LIBS analysis of zeolites. ► Calibration curves for molar ratio of Si/Al determination in three zeolites types. ► Comparison of calibration curves obtained using peak area and peak amplitude.Modelling the position of analyte emission maxima in low temperature direct current arc plasma using statistical procedures
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
J. Savović, M.S. Pavlović, M. Stoiljković, M. Kuzmanović, M. Momčilović, V. Vasić
In low temperature argon arc plasma, emission spectral lines of different analytes have characteristic radial distributions with emission maxima distributed over a wide plasma region, from the arc axis toward the arc periphery. It was assumed that the occurrence of emission maxima is a result of collective action of factors that control vaporization, dissociation, excitation, ionization and analyte transport. A statistical analysis was used to reveal a correlation between these various factors and a radial position of maximum emission. A regression analysis was used both for predictive and explanatory purposes: a model was built that successfully predicted analyte spatial emission characteristics, based on their physical properties and local plasma parameters, and a relative importance of proposed predictors was estimated.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
J. Savović, M.S. Pavlović, M. Stoiljković, M. Kuzmanović, M. Momčilović, V. Vasić
In low temperature argon arc plasma, emission spectral lines of different analytes have characteristic radial distributions with emission maxima distributed over a wide plasma region, from the arc axis toward the arc periphery. It was assumed that the occurrence of emission maxima is a result of collective action of factors that control vaporization, dissociation, excitation, ionization and analyte transport. A statistical analysis was used to reveal a correlation between these various factors and a radial position of maximum emission. A regression analysis was used both for predictive and explanatory purposes: a model was built that successfully predicted analyte spatial emission characteristics, based on their physical properties and local plasma parameters, and a relative importance of proposed predictors was estimated.
Highlights
► PCR analysis was used to model radial emission profiles in DC arc plasma. ► The main factors governing the radial distribution of atomic emission were analyzed. ► A model was built based on local plasma parameters and analyte physical properties.Investigation of materials of different crystal structure under various time delays using double pulse laser induced breakdown spectroscopy
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
E. Yurdanur-Tasel, H. Berberoglu, S. Bilikmen
The performance of a commercial, compact and portable laser induced breakdown spectroscopy (LIBS) system and a constructed laboratory LIBS system with different experimental approaches were investigated in order to make improvements in the qualitative results. One of the experimental studies pertained to the investigation of the different crystal surfaces of silicon. The second experimental study involved the polarization effects by which the polarization dependency was demonstrated. The third and final experimental study was an unconventional orthogonal double pulse configuration with a 45° angle of incidence for both lasers in opposite directions. By means of these experimental approaches reliable, reproducible results were obtained, relative intensities of the emission lines were enhanced and better signal to noise ratios were observed. Furthermore, the qualitative analysis performance of the commercial system software was compared with the code developed. The code yielded more accurate and precise analysis capability.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
E. Yurdanur-Tasel, H. Berberoglu, S. Bilikmen
The performance of a commercial, compact and portable laser induced breakdown spectroscopy (LIBS) system and a constructed laboratory LIBS system with different experimental approaches were investigated in order to make improvements in the qualitative results. One of the experimental studies pertained to the investigation of the different crystal surfaces of silicon. The second experimental study involved the polarization effects by which the polarization dependency was demonstrated. The third and final experimental study was an unconventional orthogonal double pulse configuration with a 45° angle of incidence for both lasers in opposite directions. By means of these experimental approaches reliable, reproducible results were obtained, relative intensities of the emission lines were enhanced and better signal to noise ratios were observed. Furthermore, the qualitative analysis performance of the commercial system software was compared with the code developed. The code yielded more accurate and precise analysis capability.
Highlights
► Double pulse LIBS with lasers at 45° angle to the sample is investigated. ► Si (100) emission intensities are higher than (111) due to dangling bond density. ► Plasma polarization behavior is strong at the peaks of the smaller wavelengths. ► A basic and more accurate code for the analysis of spectral lines is developed.Correlation between native bonds in a polymeric material and molecular emissions from the laser-induced plasma observed with space and time resolved imaging
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
S. Grégoire, V. Motto-Ros, Q.L. Ma, W.Q. Lei, X.C. Wang, F. Pelascini, F. Surma, V. Detalle, J. Yu
Emissions from C2 molecules and CN radicals in laser-induced plasmas on polymeric materials were observed with time-resolved spectroscopic imaging. More precisely, differential imaging with a pair of narrowband filters (one centered on the emission line and another out of the line) was used to extract emission images of interested molecules or radicals. The correlation between the molecular emission image of the plasma and the molecular structure of the polymer to be analyzed was studied for four different types of materials: polyamide (PA) with native CN bonds, polyethylene (PE) with simple CC bonds, polystyrene (PS) with delocalized double CC bonds, and polyoxymethylene (POM) which neither contains CC nor CN bonds. A clear correlation is demonstrated between emission and molecular structure of the material, allowing the identification of several organic compounds by differential spectroscopic imaging.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
S. Grégoire, V. Motto-Ros, Q.L. Ma, W.Q. Lei, X.C. Wang, F. Pelascini, F. Surma, V. Detalle, J. Yu
Emissions from C2 molecules and CN radicals in laser-induced plasmas on polymeric materials were observed with time-resolved spectroscopic imaging. More precisely, differential imaging with a pair of narrowband filters (one centered on the emission line and another out of the line) was used to extract emission images of interested molecules or radicals. The correlation between the molecular emission image of the plasma and the molecular structure of the polymer to be analyzed was studied for four different types of materials: polyamide (PA) with native CN bonds, polyethylene (PE) with simple CC bonds, polystyrene (PS) with delocalized double CC bonds, and polyoxymethylene (POM) which neither contains CC nor CN bonds. A clear correlation is demonstrated between emission and molecular structure of the material, allowing the identification of several organic compounds by differential spectroscopic imaging.
Highlights
► Plasma Imaging method to discriminate different type of polymers ► Molecular emissions (CN and C2) are spatially and temporally correlated to native bonds ► Several formation processes of molecular fragments are observedExperimental and theoretical investigations about the vaporization process of laser-produced aerosols and individual particles inside inductively-coupled plasma sources - Implications for the extraction efficiency of ions prior to mass spectrometry and accuracy of analyses
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Luca Flamigni, Joachim Koch, Detlef Günther
Current quantification capabilities of laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) are known to be restricted by elemental fractionation as a result of LA-, transport-, and ICP-induced effects which, particularly, may provoke inaccuracies whenever calibration strategies on basis of non-matrix matched standard materials are applied. The present study is dealing with the role of the ICP in this complex scenario. Therefore, the vaporization process of laser-produced aerosols and subsequent diffusion losses occurring inside ICP sources were investigated using 2-D optical emission spectrometry (OES) and ICP-quadrupole (Q)MS of individual particles. For instance, Na- and Ca-specific OES of aerosols produced by LA of silicate glasses or metals revealed axial shifts in the onset and maximum position of atomic emission which were in a range of few millimeters. The occurrence of these shifts was found to arise from composition-dependent particle/aerosol penetration depths, i.e. the displacement of axial vaporization starting points controlling the ion extraction efficiency through the ICP-MS vacuum interface due to a delayed, diffusion-driven expansion of oxidic vs. metallic aerosols. Furthermore, ICP-QMS of individual particles resulted in 1/e half-value signal durations of approximately one hundred microseconds, which complies with modeled values if OES maxima are assumed to coincide with positions of instantaneous vaporization and starting points for atomic diffusion. To prove phenomena observed for their consistency, in addition, “ab-initio” as well as semi-empirical simulations of particle/aerosol penetration depths followed by diffusion-driven expansion was accomplished indicating differences of up to 15% in the relative ion extraction efficiency depending on whether analytes are supplied as metals or oxides. Implications of these findings on the accuracy achievable by state-of-the-art LA-ICP-MS systems are outlined.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Luca Flamigni, Joachim Koch, Detlef Günther
Current quantification capabilities of laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) are known to be restricted by elemental fractionation as a result of LA-, transport-, and ICP-induced effects which, particularly, may provoke inaccuracies whenever calibration strategies on basis of non-matrix matched standard materials are applied. The present study is dealing with the role of the ICP in this complex scenario. Therefore, the vaporization process of laser-produced aerosols and subsequent diffusion losses occurring inside ICP sources were investigated using 2-D optical emission spectrometry (OES) and ICP-quadrupole (Q)MS of individual particles. For instance, Na- and Ca-specific OES of aerosols produced by LA of silicate glasses or metals revealed axial shifts in the onset and maximum position of atomic emission which were in a range of few millimeters. The occurrence of these shifts was found to arise from composition-dependent particle/aerosol penetration depths, i.e. the displacement of axial vaporization starting points controlling the ion extraction efficiency through the ICP-MS vacuum interface due to a delayed, diffusion-driven expansion of oxidic vs. metallic aerosols. Furthermore, ICP-QMS of individual particles resulted in 1/e half-value signal durations of approximately one hundred microseconds, which complies with modeled values if OES maxima are assumed to coincide with positions of instantaneous vaporization and starting points for atomic diffusion. To prove phenomena observed for their consistency, in addition, “ab-initio” as well as semi-empirical simulations of particle/aerosol penetration depths followed by diffusion-driven expansion was accomplished indicating differences of up to 15% in the relative ion extraction efficiency depending on whether analytes are supplied as metals or oxides. Implications of these findings on the accuracy achievable by state-of-the-art LA-ICP-MS systems are outlined.
Highlights
► Specification of particle/aerosol penetration depths inside ICP sources by 2-D OES ► Application of a theory describing particle vaporization and analyte diffusion ► Modeling of ICP-MS ion extraction efficiencies ► Discussion about 2-D OES as a complementary tuning strategy for LA-ICP-MSHβ Stark broadening in cold plasmas with low electron densities calibrated with Thomson scattering
02 August 2012,
08:57:43
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
J.M. Palomares, S. Hübner, E.A.D. Carbone, N. de Vries, E.M. van Veldhuizen, A. Sola, A. Gamero, J.J.A.M. v d Mullen
In the present work Stark broadening measurements have been carried out on low electron density (n e <5·1019 m−3) and (relatively) low gas temperature (T g <1100K) argon–hydrogen plasma, under low-intermediate pressure conditions (3mbar–40mbar). A line fitting procedure is used to separate the effects of the different broadening mechanisms (e.g. Doppler and instrumental broadening) from the Stark broadening. A Stark broadening theory is extrapolated to lower electron density values, below its theoretical validity regime. Thomson scattering measurements are used to calibrate and validate the procedure. The results show an agreement within 20%, what validates the use of this Stark broadening method under such low density conditions. It is also found that Stark broadened profiles cannot be assumed to be purely Lorentzian. Such an assumption would lead to an underestimation of the electron density. This implies that independent information on the gas temperature is needed to find the correct values of n e .
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
J.M. Palomares, S. Hübner, E.A.D. Carbone, N. de Vries, E.M. van Veldhuizen, A. Sola, A. Gamero, J.J.A.M. v d Mullen
In the present work Stark broadening measurements have been carried out on low electron density (n e <5·1019 m−3) and (relatively) low gas temperature (T g <1100K) argon–hydrogen plasma, under low-intermediate pressure conditions (3mbar–40mbar). A line fitting procedure is used to separate the effects of the different broadening mechanisms (e.g. Doppler and instrumental broadening) from the Stark broadening. A Stark broadening theory is extrapolated to lower electron density values, below its theoretical validity regime. Thomson scattering measurements are used to calibrate and validate the procedure. The results show an agreement within 20%, what validates the use of this Stark broadening method under such low density conditions. It is also found that Stark broadened profiles cannot be assumed to be purely Lorentzian. Such an assumption would lead to an underestimation of the electron density. This implies that independent information on the gas temperature is needed to find the correct values of n e .
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