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Surface elemental mapping via glow discharge optical emission spectroscopy
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Gerardo Gamez, Maxim Voronov, Steven J. Ray, Volker Hoffmann, Gary M. Hieftje, Johann Michler
Glow discharge optical emission spectroscopy (GDOES) has evolved in the last couple of decades from direct bulk solid analysis to a high resolution depth-profiling technique. However, the achievable lateral resolution has been historically restricted to the diameter of the sputtered area, i.e. some millimetres. Recently, there has been a push toward characterizing and improving the GDOES limits of lateral resolution. In consequence, a door has been opened for applications to take advantage of the new information dimensions that the technique affords. It is important to sum what has been accomplished so far to clarify the current possibilities and opportunities for development. It will become evident that the data acquisition requirements of GDOES elemental mapping can only be met via spectral imaging. Accordingly, the studies performed to date will be reviewed with emphasis on the spectral imaging geometry that has been utilized.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Gerardo Gamez, Maxim Voronov, Steven J. Ray, Volker Hoffmann, Gary M. Hieftje, Johann Michler
Glow discharge optical emission spectroscopy (GDOES) has evolved in the last couple of decades from direct bulk solid analysis to a high resolution depth-profiling technique. However, the achievable lateral resolution has been historically restricted to the diameter of the sputtered area, i.e. some millimetres. Recently, there has been a push toward characterizing and improving the GDOES limits of lateral resolution. In consequence, a door has been opened for applications to take advantage of the new information dimensions that the technique affords. It is important to sum what has been accomplished so far to clarify the current possibilities and opportunities for development. It will become evident that the data acquisition requirements of GDOES elemental mapping can only be met via spectral imaging. Accordingly, the studies performed to date will be reviewed with emphasis on the spectral imaging geometry that has been utilized.
Ultratrace determination of lead by hydride generation in-atomizer trapping atomic absorption spectrometry: Optimization of plumbane generation and analyte preconcentration in a quartz trap-and-atomizer device
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jan Kratzer
A compact trap-and-atomizer device and a preconcentration procedure based on hydride trapping in excess of oxygen over hydrogen in the collection step, both constructed and developed previously in our laboratory, were employed to optimize plumbane trapping in this device and to develop a routine method for ultratrace lead determination subsequently. The inherent advantage of this preconcentration approach is that 100% preconcentration efficiency for lead is reached in this device which has never been reported before using quartz or metal traps. Plumbane is completely retained in the trap-and-atomizer device at 290°C in oxygen-rich atmosphere and trapped species are subsequently volatilized at 830°C in hydrogen-rich atmosphere. Effect of relevant experimental parameters on plumbane trapping and lead volatilization are discussed, and possible trapping mechanisms are hypothesized. Plumbane trapping in the trap-and-atomizer device can be routinely used for lead determination at ultratrace levels reaching a detection limit of 0.21ngml-1 Pb (30s preconcentration, sample volume 2ml). Further improvement of the detection limit is feasible by reducing the blank signal and increasing the trapping time.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jan Kratzer
A compact trap-and-atomizer device and a preconcentration procedure based on hydride trapping in excess of oxygen over hydrogen in the collection step, both constructed and developed previously in our laboratory, were employed to optimize plumbane trapping in this device and to develop a routine method for ultratrace lead determination subsequently. The inherent advantage of this preconcentration approach is that 100% preconcentration efficiency for lead is reached in this device which has never been reported before using quartz or metal traps. Plumbane is completely retained in the trap-and-atomizer device at 290°C in oxygen-rich atmosphere and trapped species are subsequently volatilized at 830°C in hydrogen-rich atmosphere. Effect of relevant experimental parameters on plumbane trapping and lead volatilization are discussed, and possible trapping mechanisms are hypothesized. Plumbane trapping in the trap-and-atomizer device can be routinely used for lead determination at ultratrace levels reaching a detection limit of 0.21ngml-1 Pb (30s preconcentration, sample volume 2ml). Further improvement of the detection limit is feasible by reducing the blank signal and increasing the trapping time.
Development of an analytical method for the determination of arsenic in gasoline samples by hydride generation-graphite furnace atomic absorption spectrometry
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Emilene M. Becker, Morgana B. Dessuy, Wiliam Boschetti, Maria Goreti R. Vale, Sérgio L.C. Ferreira, Bernhard Welz
The purpose of the present work was to optimize the conditions for the determination of arsenic in gasoline with hydride generation-graphite furnace atomic absorption spectrometry after acid digestion using a full two-level factorial design with center point. The arsine was generated in a batch system and collected in a graphite tube coated with 150μg Ir as a permanent modifier. The sample volume, the pre-reduction conditions, the temperature program and modifier mass were kept fixed for all experiments. The estimated main effects were: reducing agent concentration (negative effect), acid concentration (negative effect) and trapping temperature (positive effect). It was observed that there were interactions between the variables. Moreover, the curvature was significant, indicating that the best conditions were at the center point. The optimized parameters for arsine generation were 2.7molL-1 hydrochloric acid and 1.6% (w/v) sodium tetrahydroborate. The optimized conditions to collect arsine in the graphite furnace were a trapping temperature of 250°C and a collection time of 30s. The limit of detection was 6.4ngL-1 and the characteristic mass was 24pg. Two different systems for acid digestion were used: a digester block with cold finger and a microwave oven. The concentration of arsenic found with the proposed method was compared with that obtained using a detergentless microemulsion and direct graphite furnace determination. The results showed that the factorial design is a simple tool that allowed establishing the appropriate conditions for sample preparation and also helped evaluating the interaction between the factors investigated.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Emilene M. Becker, Morgana B. Dessuy, Wiliam Boschetti, Maria Goreti R. Vale, Sérgio L.C. Ferreira, Bernhard Welz
The purpose of the present work was to optimize the conditions for the determination of arsenic in gasoline with hydride generation-graphite furnace atomic absorption spectrometry after acid digestion using a full two-level factorial design with center point. The arsine was generated in a batch system and collected in a graphite tube coated with 150μg Ir as a permanent modifier. The sample volume, the pre-reduction conditions, the temperature program and modifier mass were kept fixed for all experiments. The estimated main effects were: reducing agent concentration (negative effect), acid concentration (negative effect) and trapping temperature (positive effect). It was observed that there were interactions between the variables. Moreover, the curvature was significant, indicating that the best conditions were at the center point. The optimized parameters for arsine generation were 2.7molL-1 hydrochloric acid and 1.6% (w/v) sodium tetrahydroborate. The optimized conditions to collect arsine in the graphite furnace were a trapping temperature of 250°C and a collection time of 30s. The limit of detection was 6.4ngL-1 and the characteristic mass was 24pg. Two different systems for acid digestion were used: a digester block with cold finger and a microwave oven. The concentration of arsenic found with the proposed method was compared with that obtained using a detergentless microemulsion and direct graphite furnace determination. The results showed that the factorial design is a simple tool that allowed establishing the appropriate conditions for sample preparation and also helped evaluating the interaction between the factors investigated.
Clustering and Training Set Selection Methods for Improving the Accuracy of Quantitative Laser Induced Breakdown Spectroscopy
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Ryan B. Anderson, James F. Bell, Roger C. Wiens, Richard V. Morris, Samuel M. Clegg
We investigated five clustering and training set selection methods to improve the accuracy of quantitative chemical analysis of geologic samples by laser induced breakdown spectroscopy (LIBS) using partial least squares (PLS) regression. The LIBS spectra were previously acquired for 195 rock slabs and 31 pressed powder geostandards under 7Torr CO2 at a stand-off distance of 7m at 17mJ per pulse to simulate the operational conditions of the ChemCam LIBS instrument on the Mars Science Laboratory Curiosity rover. The clustering and training set selection methods, which do not require prior knowledge of the chemical composition of the test-set samples, are based on grouping similar spectra and selecting appropriate training spectra for the partial least squares (PLS2) model. These methods were: (1) Hierarchical clustering of the full set of training spectra and selection of a subset for use in training; (2) K-means clustering of all spectra and generation of PLS2 models based on the training samples within each cluster; (3) Iterative use of PLS2 to predict sample composition and k-means clustering of the predicted compositions to subdivide the groups of spectra; (4) Soft independent modeling of class analogy (SIMCA) classification of spectra, and generation of PLS2 models based on the training samples within each class; (5) Use of Bayesian information criteria (BIC) to determine an optimal number of clusters and generation of PLS2 models based on the training samples within each cluster. The iterative method and the k-means method using 5 clusters showed the best performance, improving the absolute quadrature root mean squared error (RMSE) by ~3 wt. %. The statistical significance of these improvements was ~85%. Our results show that although clustering methods can modestly improve results, a large and diverse training set is the most reliable way to improve the accuracy of quantitative LIBS. In particular, additional sulfate standards and specifically fabricated analog samples with Mars-like compositions may improve the accuracy of ChemCam measurements on Mars. Refinement of the iterative method, modifications of the basic k-means clustering algorithm, and classification based on specifically selected S, C and Si emission lines may also prove beneficial and merit further study.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Ryan B. Anderson, James F. Bell, Roger C. Wiens, Richard V. Morris, Samuel M. Clegg
We investigated five clustering and training set selection methods to improve the accuracy of quantitative chemical analysis of geologic samples by laser induced breakdown spectroscopy (LIBS) using partial least squares (PLS) regression. The LIBS spectra were previously acquired for 195 rock slabs and 31 pressed powder geostandards under 7Torr CO2 at a stand-off distance of 7m at 17mJ per pulse to simulate the operational conditions of the ChemCam LIBS instrument on the Mars Science Laboratory Curiosity rover. The clustering and training set selection methods, which do not require prior knowledge of the chemical composition of the test-set samples, are based on grouping similar spectra and selecting appropriate training spectra for the partial least squares (PLS2) model. These methods were: (1) Hierarchical clustering of the full set of training spectra and selection of a subset for use in training; (2) K-means clustering of all spectra and generation of PLS2 models based on the training samples within each cluster; (3) Iterative use of PLS2 to predict sample composition and k-means clustering of the predicted compositions to subdivide the groups of spectra; (4) Soft independent modeling of class analogy (SIMCA) classification of spectra, and generation of PLS2 models based on the training samples within each class; (5) Use of Bayesian information criteria (BIC) to determine an optimal number of clusters and generation of PLS2 models based on the training samples within each cluster. The iterative method and the k-means method using 5 clusters showed the best performance, improving the absolute quadrature root mean squared error (RMSE) by ~3 wt. %. The statistical significance of these improvements was ~85%. Our results show that although clustering methods can modestly improve results, a large and diverse training set is the most reliable way to improve the accuracy of quantitative LIBS. In particular, additional sulfate standards and specifically fabricated analog samples with Mars-like compositions may improve the accuracy of ChemCam measurements on Mars. Refinement of the iterative method, modifications of the basic k-means clustering algorithm, and classification based on specifically selected S, C and Si emission lines may also prove beneficial and merit further study.
Application of methane as a gaseous modifier for the determination of silicon using electrothermal atomic absorption spectrometry
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Hans-Joachim Heinrich, Heinrich Kipphardt
For determination of silicon in aqueous solutions by electrothermal atomic absorption spectrometry methane/argon mixtures as a gaseous modifier were applied during the pyrolysis step to improve the analytical performance. The beneficial effects observed on thermal stabilization, signal enhancement and shape of absorbance signals were attributed to the thermal decomposition products of methane, which were hydrogen and carbon black (soot). Using a 5% CH4 mixture with argon, the optimized pyrolysis and atomization temperatures were 1350°C and 2450°C, respectively. A flushing step following the pyrolysis was mandatory to avoid background absorption and accelerated deposition of pyrolytic graphite. Characteristic masses of 50 and 30pg were obtained for standard transverse heated graphite atomizer (THGA) tubes and end-capped THGA tubes, respectively, which were lower than with other previously applied modifiers. A limit of detection of 0.2μgL-1 (3 s, n =10) has been obtained. In addition, this gaseous modifier did not contribute to contamination which often was significant when a liquid modifier solution was co-injected. The proposed method has been applied to the determination of silicon in ultrapure water, nitric and hydrochloric acids.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Hans-Joachim Heinrich, Heinrich Kipphardt
For determination of silicon in aqueous solutions by electrothermal atomic absorption spectrometry methane/argon mixtures as a gaseous modifier were applied during the pyrolysis step to improve the analytical performance. The beneficial effects observed on thermal stabilization, signal enhancement and shape of absorbance signals were attributed to the thermal decomposition products of methane, which were hydrogen and carbon black (soot). Using a 5% CH4 mixture with argon, the optimized pyrolysis and atomization temperatures were 1350°C and 2450°C, respectively. A flushing step following the pyrolysis was mandatory to avoid background absorption and accelerated deposition of pyrolytic graphite. Characteristic masses of 50 and 30pg were obtained for standard transverse heated graphite atomizer (THGA) tubes and end-capped THGA tubes, respectively, which were lower than with other previously applied modifiers. A limit of detection of 0.2μgL-1 (3 s, n =10) has been obtained. In addition, this gaseous modifier did not contribute to contamination which often was significant when a liquid modifier solution was co-injected. The proposed method has been applied to the determination of silicon in ultrapure water, nitric and hydrochloric acids.
The behavior of various chemical forms of nickel in graphite furnace atomic absorption spectrometry under different chemical modification approaches
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Zofia Kowalewska
Various organic and inorganic Ni forms were investigated using graphite furnace atomic absorption spectrometry. Experiments without chemical modification showed a wide range of characteristic mass values for Ni (from 6.7 to 29pg) and the importance of interaction with graphite. With the aim of achieving signal unification of organic Ni forms, different ways of chemical modification were tested. Some rules that govern the behavior of Ni were found and confirmed a significant role of the organic component of the analyte molecule in the analytical process. The application of air as an internal furnace gas in the pyrolysis phase and the Pd modifier injected with the sample solution improved the signal of porphyrins, while the application of iodine and methyltrioctylammonium chloride was required for organic compounds containing oxygen-bound Ni atoms. The Ni signal was strongly diminished when an aqueous solution containing hydrochloric acid was measured with the Pd modifier injected over the sample. Using the developed analytical methods, the range of characteristic mass values for various Ni forms totally dissolved in organic or aqueous solution was 6.5-7.9pg.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Zofia Kowalewska
Various organic and inorganic Ni forms were investigated using graphite furnace atomic absorption spectrometry. Experiments without chemical modification showed a wide range of characteristic mass values for Ni (from 6.7 to 29pg) and the importance of interaction with graphite. With the aim of achieving signal unification of organic Ni forms, different ways of chemical modification were tested. Some rules that govern the behavior of Ni were found and confirmed a significant role of the organic component of the analyte molecule in the analytical process. The application of air as an internal furnace gas in the pyrolysis phase and the Pd modifier injected with the sample solution improved the signal of porphyrins, while the application of iodine and methyltrioctylammonium chloride was required for organic compounds containing oxygen-bound Ni atoms. The Ni signal was strongly diminished when an aqueous solution containing hydrochloric acid was measured with the Pd modifier injected over the sample. Using the developed analytical methods, the range of characteristic mass values for various Ni forms totally dissolved in organic or aqueous solution was 6.5-7.9pg.
Electrochemical generation of volatile lead species using a cadmium cathode: Comparison with graphite, glassy carbon and platinum cathodes
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
María Saénz, Lenys Fernández, José Domínguez, José Alvarado
Working electrodes made out of pyrolytic graphite, glassy carbon, platinum and cadmium were compared for the electrochemical generation of volatile lead species. The same electrolytic cell, using each of the different working electrodes was coupled to an atomic absorption spectrometer and the experimental conditions were optimized in each case, using a univariate approach, to produce the maximum possible amount of volatile lead species. The experiments were focused on the variation of cathode hydrogen overvoltage by the application of a constant current during analysis. Under optimum conditions the performance of the electrochemical hydride generator cell should depend on the cathode material selected due to the different hydrogen overpotential of each material. The lead absorbance signal was taken as a measure of the efficiency of volatile lead species production. Best results were obtained using the Cd cathode, due to its relatively highest hydrogen overpotential, a carrier gas (Ar) flow rate of 55mLmin-1 an electrolytic current of 0.8 A and a catholyte (HCl) concentration 0.05molL-1. The analytical figures of merit of the method using the Cd electrode were evaluated and the susceptibility of the method to interferences was assessed by its application to the determination of trace amounts of lead in the presence of the most significant interferents. The calibration curve was linear between 0.5 - 15μgL-1 Pb. Detection limits and and characteristic mass values were 0.21μgL-1 and 0.26μgL-1 respectively. A bovine liver Standard Reference Material and a spiked urine sample were analyzed to check accuracy.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
María Saénz, Lenys Fernández, José Domínguez, José Alvarado
Working electrodes made out of pyrolytic graphite, glassy carbon, platinum and cadmium were compared for the electrochemical generation of volatile lead species. The same electrolytic cell, using each of the different working electrodes was coupled to an atomic absorption spectrometer and the experimental conditions were optimized in each case, using a univariate approach, to produce the maximum possible amount of volatile lead species. The experiments were focused on the variation of cathode hydrogen overvoltage by the application of a constant current during analysis. Under optimum conditions the performance of the electrochemical hydride generator cell should depend on the cathode material selected due to the different hydrogen overpotential of each material. The lead absorbance signal was taken as a measure of the efficiency of volatile lead species production. Best results were obtained using the Cd cathode, due to its relatively highest hydrogen overpotential, a carrier gas (Ar) flow rate of 55mLmin-1 an electrolytic current of 0.8 A and a catholyte (HCl) concentration 0.05molL-1. The analytical figures of merit of the method using the Cd electrode were evaluated and the susceptibility of the method to interferences was assessed by its application to the determination of trace amounts of lead in the presence of the most significant interferents. The calibration curve was linear between 0.5 - 15μgL-1 Pb. Detection limits and and characteristic mass values were 0.21μgL-1 and 0.26μgL-1 respectively. A bovine liver Standard Reference Material and a spiked urine sample were analyzed to check accuracy.
Determination of chlorine in food samples via the AlCl molecule using high-resolution continuum source molecular absorption spectrometry in a graphite furnace
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Miriam Fechetia, André Luiz Tognon, Márcia A.M.S. da Veiga
Determination of chlorine using the molecular absorption of aluminum mono-chloride (AlCl) at the 261.418nm wavelength was accomplished by high-resolution continuum source molecular absorption spectrometry using a transversely heated graphite tube furnace with an integrated platform. For the analysis, 10 μL of the sample followed by 10 μL of a solution containing Al-Ag-Sr modifier, (1gL-1 each), were directly injected onto the platform. A spectral interference due to the use of Al-Ag-Sr as mixed modifier was easily corrected by the least-squares algorithm present in the spectrometer software. The pyrolysis and vaporization temperatures were 500°C and 2200°C, respectively. To evaluate the feasibility of a simple procedure for the determination of chlorine in food samples present in our daily lives, two different digestion methods were applied, namely (A) an acid digestion method using HNO3 only at room temperature, and (B) a digestion method with Ag, HNO3 and H2O2, where chlorine is precipitated as a low-solubility salt (AgCl), which is then dissolved with ammonia solution. The experimental results obtained with method B were in good agreement with the certified values and demonstrated that the proposed method is more accurate than method A. This is because the formation of silver chloride prevented analyte losses by volatilization. The limit of detection (LOD, 3σ/s) for Cl in methods A and B was 18μgg-1 and 9μgg-1, respectively, 1.7 and 3.3 times lower compared to published work using inductively coupled plasma optical emission spectrometry, and absolute LODs were 2.4 and 1.2ng, respectively.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Miriam Fechetia, André Luiz Tognon, Márcia A.M.S. da Veiga
Determination of chlorine using the molecular absorption of aluminum mono-chloride (AlCl) at the 261.418nm wavelength was accomplished by high-resolution continuum source molecular absorption spectrometry using a transversely heated graphite tube furnace with an integrated platform. For the analysis, 10 μL of the sample followed by 10 μL of a solution containing Al-Ag-Sr modifier, (1gL-1 each), were directly injected onto the platform. A spectral interference due to the use of Al-Ag-Sr as mixed modifier was easily corrected by the least-squares algorithm present in the spectrometer software. The pyrolysis and vaporization temperatures were 500°C and 2200°C, respectively. To evaluate the feasibility of a simple procedure for the determination of chlorine in food samples present in our daily lives, two different digestion methods were applied, namely (A) an acid digestion method using HNO3 only at room temperature, and (B) a digestion method with Ag, HNO3 and H2O2, where chlorine is precipitated as a low-solubility salt (AgCl), which is then dissolved with ammonia solution. The experimental results obtained with method B were in good agreement with the certified values and demonstrated that the proposed method is more accurate than method A. This is because the formation of silver chloride prevented analyte losses by volatilization. The limit of detection (LOD, 3σ/s) for Cl in methods A and B was 18μgg-1 and 9μgg-1, respectively, 1.7 and 3.3 times lower compared to published work using inductively coupled plasma optical emission spectrometry, and absolute LODs were 2.4 and 1.2ng, respectively.
A general Monte Carlo simulation of energy dispersive X-ray fluorescence spectrometers — Part 5 Polarized radiation, stratified samples, cascade effects, M-lines
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Tom Schoonjans, Laszlo Vincze, Vicente Armando Solé, Manuel Sanchez del Rio, Philip Brondeel, Geert Silversmit, Karen Appel, Claudio Ferrero
A general Monte Carlo code for the simulation of energy dispersive X-ray fluorescence (ED-XRF) spectrometers is presented. As a significant extension to existing Monte Carlo codes, dedicated to ED-XRF spectrometers, the new code includes several unique features such as the simulation of M-lines and cascade effects. The detector response function was extended with fluorescence and Compton escape peaks, as well as with pulse pile-up. A full description of the underlying algorithms is given. The software was validated by means of comparison with experimental spectra of standard reference materials collected at the synchrotron XRF-microprobe installed at HASYLAB Beamline L, Hamburg, Germany.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Tom Schoonjans, Laszlo Vincze, Vicente Armando Solé, Manuel Sanchez del Rio, Philip Brondeel, Geert Silversmit, Karen Appel, Claudio Ferrero
A general Monte Carlo code for the simulation of energy dispersive X-ray fluorescence (ED-XRF) spectrometers is presented. As a significant extension to existing Monte Carlo codes, dedicated to ED-XRF spectrometers, the new code includes several unique features such as the simulation of M-lines and cascade effects. The detector response function was extended with fluorescence and Compton escape peaks, as well as with pulse pile-up. A full description of the underlying algorithms is given. The software was validated by means of comparison with experimental spectra of standard reference materials collected at the synchrotron XRF-microprobe installed at HASYLAB Beamline L, Hamburg, Germany.
High-resolution continuum source electrothermal atomic absorption spectrometry: Linearization of the calibration curves within a broad concentration range
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Dmitri Katskov, Miranda Hlongwane, Uwe Heitmann, Stefan Florek
The calculation algorithm suggested provides linearization of the calibration curves in high-resolution continuum source electrothermal atomic absorption spectrometry. The algorithm is based on the modification of the function wavelength-integrated absorbance vs. concentration of analyte vapor in the absorption volume. According to the suggested approach, the absorption line is represented by a triangle for low and trapezium for high analyte vapor concentration in the absorption volume. The respective semi-empirical formulas include two linearization parameters, which depend on properties of the absorption line and characteristics of the atomizer and spectrometer. The parameters can be approximately evaluated from the theory and determined in practice from the original broad-range calibration curve. The parameters were found and the proposed calculation algorithm verified in the experiments on direct determination of Ag, Cd, Cu, Fe, Mn and Pb in the solutions within a concentration ranges from 0.15 to 625μg·L−1 using tube, platform tube and filter furnace atomizers. The use of various atomizers, lines, elements and atomization temperatures made possible the simulation of various practical analytical conditions. It was found that the algorithm and optimal linearization parameters made it possible to obtain for each line and atomizer linear approximations of the calibration curves within 3–4 orders of magnitude with correlation coefficients close to 0.999. The algorithm makes possible to employ a single line for the direct element determination over a broad concentration range. The sources of errors and the possibility of a priori theoretical evaluation of the linearization parameters are discussed.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Dmitri Katskov, Miranda Hlongwane, Uwe Heitmann, Stefan Florek
The calculation algorithm suggested provides linearization of the calibration curves in high-resolution continuum source electrothermal atomic absorption spectrometry. The algorithm is based on the modification of the function wavelength-integrated absorbance vs. concentration of analyte vapor in the absorption volume. According to the suggested approach, the absorption line is represented by a triangle for low and trapezium for high analyte vapor concentration in the absorption volume. The respective semi-empirical formulas include two linearization parameters, which depend on properties of the absorption line and characteristics of the atomizer and spectrometer. The parameters can be approximately evaluated from the theory and determined in practice from the original broad-range calibration curve. The parameters were found and the proposed calculation algorithm verified in the experiments on direct determination of Ag, Cd, Cu, Fe, Mn and Pb in the solutions within a concentration ranges from 0.15 to 625μg·L−1 using tube, platform tube and filter furnace atomizers. The use of various atomizers, lines, elements and atomization temperatures made possible the simulation of various practical analytical conditions. It was found that the algorithm and optimal linearization parameters made it possible to obtain for each line and atomizer linear approximations of the calibration curves within 3–4 orders of magnitude with correlation coefficients close to 0.999. The algorithm makes possible to employ a single line for the direct element determination over a broad concentration range. The sources of errors and the possibility of a priori theoretical evaluation of the linearization parameters are discussed.
Determination of arsenic and cadmium in crude oil by direct sampling graphite furnace atomic absorption spectrometry
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Alexandre de Jesus, Ariane Vanessa Zmozinski, Isabel Cristina Ferreira Damin, Márcia Messias Silva, Maria Goreti Rodrigues Vale
In this work, a direct sampling graphite furnace atomic absorption spectrometry method has been developed for the determination of arsenic and cadmium in crude oil samples. The samples were weighed directly on the solid sampling platforms and introduced into the graphite tube for analysis. The chemical modifier used for both analytes was a mixture of 0.1% Pd+0.06% Mg+0.06% Triton X-100. Pyrolysis and atomization curves were obtained for both analytes using standards and samples. Calibration curves with aqueous standards could be used for both analytes. The limits of detection obtained were 5.1μgkg−1 for arsenic and 0.2μgkg−1 for cadmium, calculated for the maximum amount of sample that can be analyzed (8mg and 10mg) for arsenic and cadmium, respectively. Relative standard deviations lower than 20% were obtained. For validation purposes, a calibration curve was constructed with the SRM 1634c and aqueous standards for arsenic and the results obtained for several crude oil samples were in agreement according to paired t-test. The result obtained for the determination of arsenic in the SRM against aqueous standards was also in agreement with the certificate value. As there is no crude oil or similar reference material available with a certified value for cadmium, a digestion in an open vessel under reflux using a “cold finger” was adopted for validation purposes. The use of paired t-test showed that the results obtained by direct sampling and digestion were in agreement at a 95% confidence level. Recovery tests were carried out with inorganic and organic standards and the results were between 88% and 109%. The proposed method is simple, fast and reliable, being appropriated for routine analysis.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Alexandre de Jesus, Ariane Vanessa Zmozinski, Isabel Cristina Ferreira Damin, Márcia Messias Silva, Maria Goreti Rodrigues Vale
In this work, a direct sampling graphite furnace atomic absorption spectrometry method has been developed for the determination of arsenic and cadmium in crude oil samples. The samples were weighed directly on the solid sampling platforms and introduced into the graphite tube for analysis. The chemical modifier used for both analytes was a mixture of 0.1% Pd+0.06% Mg+0.06% Triton X-100. Pyrolysis and atomization curves were obtained for both analytes using standards and samples. Calibration curves with aqueous standards could be used for both analytes. The limits of detection obtained were 5.1μgkg−1 for arsenic and 0.2μgkg−1 for cadmium, calculated for the maximum amount of sample that can be analyzed (8mg and 10mg) for arsenic and cadmium, respectively. Relative standard deviations lower than 20% were obtained. For validation purposes, a calibration curve was constructed with the SRM 1634c and aqueous standards for arsenic and the results obtained for several crude oil samples were in agreement according to paired t-test. The result obtained for the determination of arsenic in the SRM against aqueous standards was also in agreement with the certificate value. As there is no crude oil or similar reference material available with a certified value for cadmium, a digestion in an open vessel under reflux using a “cold finger” was adopted for validation purposes. The use of paired t-test showed that the results obtained by direct sampling and digestion were in agreement at a 95% confidence level. Recovery tests were carried out with inorganic and organic standards and the results were between 88% and 109%. The proposed method is simple, fast and reliable, being appropriated for routine analysis.
Direct solid sampling electrothermal atomic absorption spectrometric determination of toxic and potentially toxic elements in certified reference materials of brown coal fly ash
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Peter Török, Mária Žemberyová
This work describes a method for the direct determination of Bi, Cd, Cr, Ni, Pb, Sb, Sn and Zn in reference materials of brown coal fly ash, using solid sampling electrothermal atomic absorption spectrometry. The use of chemical modifiers was found to be necessary for obtaining reproducible and sufficiently sensitive signals for the analytes under study. The mixture of Pd and Mg(NO3)2 was used for the determination of Bi, Cd, Pb, Sb, Sn and Zn, W (permanent modifier) in combination with Mg(NO3)2 (as aqueous modifier) provided well-defined signal profiles for Cr and Ni determination in coal fly ash samples. A systematic study focused on the use of alternative (less sensitive) lines for obtaining sufficient sensitivity. The following analytical lines were used: Bi 306.8nm, Cd 326.1nm, Cr 520.6nm, Ni 305.1nm, Pb 205.3nm, Sb 206.8nm, Sn 300.9nm, Zn 307.6nm. The limits of detection were 0.057μg g−1 for Bi, 0.21μg g−1 for Cd, 1.1μg g−1 for Cr, 1.4μg g−1 for Ni, 4.0μg g−1 for Pb, 0.13μg g−1 for Sb, 0.33μg g−1 for Sn and 16μg g−1 for Zn, respectively.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Peter Török, Mária Žemberyová
This work describes a method for the direct determination of Bi, Cd, Cr, Ni, Pb, Sb, Sn and Zn in reference materials of brown coal fly ash, using solid sampling electrothermal atomic absorption spectrometry. The use of chemical modifiers was found to be necessary for obtaining reproducible and sufficiently sensitive signals for the analytes under study. The mixture of Pd and Mg(NO3)2 was used for the determination of Bi, Cd, Pb, Sb, Sn and Zn, W (permanent modifier) in combination with Mg(NO3)2 (as aqueous modifier) provided well-defined signal profiles for Cr and Ni determination in coal fly ash samples. A systematic study focused on the use of alternative (less sensitive) lines for obtaining sufficient sensitivity. The following analytical lines were used: Bi 306.8nm, Cd 326.1nm, Cr 520.6nm, Ni 305.1nm, Pb 205.3nm, Sb 206.8nm, Sn 300.9nm, Zn 307.6nm. The limits of detection were 0.057μg g−1 for Bi, 0.21μg g−1 for Cd, 1.1μg g−1 for Cr, 1.4μg g−1 for Ni, 4.0μg g−1 for Pb, 0.13μg g−1 for Sb, 0.33μg g−1 for Sn and 16μg g−1 for Zn, respectively.
Characterization of ancient glass excavated in Enez (Ancient Ainos) Turkey by combined Instrumental Neutron Activation Analysis and Fourier Transform Infrared spectrometry techniques
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Sevim Akyuz, Tanil Akyuz, Nuranya M. Mukhamedshina, A. Adiba Mirsagatova, Sait Basaran, Banu Cakan
Ancient glass fragments excavated in the archaeological district Enez (Ancient Ainos)–Turkey were investigated by combined Instrumental Neutron Activation Analysis (INAA) and Fourier Transform Infrared (FTIR) spectrometry techniques. Multi-elemental contents of 15 glass fragments that belong to Hellenistic, Roman, Byzantine, and Ottoman Periods, were determined by INAA. The concentrations of twenty six elements (Na, K, Ca, Sc, Cr, Mn, Fe, Co, Cu, Zn, As, Rb, Sr, Sb, Cs, Ba, Ce, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Au and Th), which might be present in the samples as flux, stabilizers, colorants or opacifiers, and impurities, were examined. Chemometric treatment of the INAA data was performed and principle component analysis revealed presence of 3 distinct groups. The thermal history of the glass samples was determined by FTIR spectrometry.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Sevim Akyuz, Tanil Akyuz, Nuranya M. Mukhamedshina, A. Adiba Mirsagatova, Sait Basaran, Banu Cakan
Ancient glass fragments excavated in the archaeological district Enez (Ancient Ainos)–Turkey were investigated by combined Instrumental Neutron Activation Analysis (INAA) and Fourier Transform Infrared (FTIR) spectrometry techniques. Multi-elemental contents of 15 glass fragments that belong to Hellenistic, Roman, Byzantine, and Ottoman Periods, were determined by INAA. The concentrations of twenty six elements (Na, K, Ca, Sc, Cr, Mn, Fe, Co, Cu, Zn, As, Rb, Sr, Sb, Cs, Ba, Ce, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Au and Th), which might be present in the samples as flux, stabilizers, colorants or opacifiers, and impurities, were examined. Chemometric treatment of the INAA data was performed and principle component analysis revealed presence of 3 distinct groups. The thermal history of the glass samples was determined by FTIR spectrometry.
Direct analysis of silica by means of solid sampling graphite furnace atomic absorption spectrometry
27 April 2012,
09:27:13
Publication year:
2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
M. Resano, E. Mozas, C. Crespo, J. Pérez, E. García-Ruiz, M.A. Belarra
This paper reports on the use of solid sampling-graphite furnace atomic absorption spectrometry for the direct analysis of synthetic amorphous silica. In particular, determination of hazardous elements such As, Cd, Cr, Cu, Pb and Sb is investigated, as required by regulations of the food industry. The conclusion of the work is that, after proper optimization of the working conditions, paying particular attention to the atomization temperature and the use of proper modifiers (graphite powder, HNO3 or Pd), it is possible to develop suitable procedures that rely on the use of aqueous standard solutions to construct the calibration curves for all the elements investigated. The proposed method shows important benefits for the cost-effective analysis of such difficult samples in routine labs, permitting fast screening of those elements that are very rarely present in this type of sample, but also accurate quantification of those often found, while offering low limits of detection (always below 0.1mgg−1) that comply well with legal requirements, and precision levels that are fit for the purpose (approx. 6–9% R.S.D.).
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
M. Resano, E. Mozas, C. Crespo, J. Pérez, E. García-Ruiz, M.A. Belarra
This paper reports on the use of solid sampling-graphite furnace atomic absorption spectrometry for the direct analysis of synthetic amorphous silica. In particular, determination of hazardous elements such As, Cd, Cr, Cu, Pb and Sb is investigated, as required by regulations of the food industry. The conclusion of the work is that, after proper optimization of the working conditions, paying particular attention to the atomization temperature and the use of proper modifiers (graphite powder, HNO3 or Pd), it is possible to develop suitable procedures that rely on the use of aqueous standard solutions to construct the calibration curves for all the elements investigated. The proposed method shows important benefits for the cost-effective analysis of such difficult samples in routine labs, permitting fast screening of those elements that are very rarely present in this type of sample, but also accurate quantification of those often found, while offering low limits of detection (always below 0.1mgg−1) that comply well with legal requirements, and precision levels that are fit for the purpose (approx. 6–9% R.S.D.).
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