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papers from the latest issue:
Production of aerosols by optical catapulting: Imaging, performance parameters and laser-induced plasma sampling rate
16 September 2013,
08:53:11
Publication date: 1 November
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 89
Author(s): M. Abdelhamid , F.J. Fortes , A. Fernández-Bravo , M.A. Harith , J.J. Laserna
Optical catapulting (OC) is a sampling and manipulation method that has been extensively studied in applications ranging from single cells in heterogeneous tissue samples to analysis of explosive residues in human fingerprints. Specifically, analysis of the catapulted material by means of laser-induced breakdown spectroscopy (LIBS) offers a promising approach for the inspection of solid particulate matter. In this work, we focus our attention in the experimental parameters to be optimized for a proper aerosol generation while increasing the particle density in the focal region sampled by LIBS. For this purpose we use shadowgraphy visualization as a diagnostic tool. Shadowgraphic images were acquired for studying the evolution and dynamics of solid aerosols produced by OC. Aluminum silicate particles (0.2–8μm) were ejected from the substrate using a Q-switched Nd:YAG laser at 1064nm, while time-resolved images recorded the propagation of the generated aerosol. For LIBS analysis and shadowgraphy visualization, a Q-switched Nd:YAG laser at 1064nm and 532nm was employed, respectively. Several parameters such as the time delay between pulses and the effect of laser fluence on the aerosol production have been also investigated. After optimization, the particle density in the sampling focal volume increases while improving the aerosol sampling rate till ca. 90%.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 89
Author(s): M. Abdelhamid , F.J. Fortes , A. Fernández-Bravo , M.A. Harith , J.J. Laserna
Optical catapulting (OC) is a sampling and manipulation method that has been extensively studied in applications ranging from single cells in heterogeneous tissue samples to analysis of explosive residues in human fingerprints. Specifically, analysis of the catapulted material by means of laser-induced breakdown spectroscopy (LIBS) offers a promising approach for the inspection of solid particulate matter. In this work, we focus our attention in the experimental parameters to be optimized for a proper aerosol generation while increasing the particle density in the focal region sampled by LIBS. For this purpose we use shadowgraphy visualization as a diagnostic tool. Shadowgraphic images were acquired for studying the evolution and dynamics of solid aerosols produced by OC. Aluminum silicate particles (0.2–8μm) were ejected from the substrate using a Q-switched Nd:YAG laser at 1064nm, while time-resolved images recorded the propagation of the generated aerosol. For LIBS analysis and shadowgraphy visualization, a Q-switched Nd:YAG laser at 1064nm and 532nm was employed, respectively. Several parameters such as the time delay between pulses and the effect of laser fluence on the aerosol production have been also investigated. After optimization, the particle density in the sampling focal volume increases while improving the aerosol sampling rate till ca. 90%.
Direct quantification of TiO2 nanoparticles in suspension by grazing-incidence X-ray fluorescence spectrometry: Influence of substrate pre-treatment in the deposition process
16 September 2013,
08:53:11
Publication date: 1 October
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): S. Motellier , S. Derrough , D. Locatelli , M. Amdaoud , K. Lhaute
X-ray fluorescence at grazing incidence (GIXRF) was investigated as a method for the quantification of TiO2 nanoparticles in aqueous suspensions. One of the major advantages of this technique is the possibility to analyze the particles without pre-treatment, like harsh acid digestion, as required by most other conventional methods. However, reliable quantitative measurements require a number of precautions. Particularly, the deposition process of the sample on the flat reflecting substrate must maintain homogeneity in composition and concentration over the entire surface of the deposition residue once dried. Scanning electron microscopy showed that using an adhesive coating of the substrate significantly improves the morphology and chemical homogeneity of the residue, hence leading to better performance of the method from a quantitative point of view. Linear calibration curves using internal standardization were established with ionic Ti and with two different types of TiO2 nanoparticles. Low limits of detections of 18μgL−1 and 52μgL−1 at incident angles of 0.20° and 0.75°, respectively, were obtained. It was found that correlation factors of the calibration linear fits were particle-size dependent, which was assigned to sampling problems due to possible incomplete dispersion of the particles in suspensions. The measured fluorescence of the dried deposits changed within a 4-month timespan for both types of TiO2 nanoparticles, demonstrating the very peculiar behavior of these particulate samples.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): S. Motellier , S. Derrough , D. Locatelli , M. Amdaoud , K. Lhaute
X-ray fluorescence at grazing incidence (GIXRF) was investigated as a method for the quantification of TiO2 nanoparticles in aqueous suspensions. One of the major advantages of this technique is the possibility to analyze the particles without pre-treatment, like harsh acid digestion, as required by most other conventional methods. However, reliable quantitative measurements require a number of precautions. Particularly, the deposition process of the sample on the flat reflecting substrate must maintain homogeneity in composition and concentration over the entire surface of the deposition residue once dried. Scanning electron microscopy showed that using an adhesive coating of the substrate significantly improves the morphology and chemical homogeneity of the residue, hence leading to better performance of the method from a quantitative point of view. Linear calibration curves using internal standardization were established with ionic Ti and with two different types of TiO2 nanoparticles. Low limits of detections of 18μgL−1 and 52μgL−1 at incident angles of 0.20° and 0.75°, respectively, were obtained. It was found that correlation factors of the calibration linear fits were particle-size dependent, which was assigned to sampling problems due to possible incomplete dispersion of the particles in suspensions. The measured fluorescence of the dried deposits changed within a 4-month timespan for both types of TiO2 nanoparticles, demonstrating the very peculiar behavior of these particulate samples.
The use of laser-induced breakdown spectroscopy for the determination of fluorine concentration in glass ionomer cement
16 September 2013,
08:53:11
Publication date: 1 October
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): T. Kratochvíl , M. Pouzar , K. Novotný , V. Havránek , T. Černohorský , M. Zvolská
The influence of He atmosphere and gate width in laser-induced breakdown spectroscopy (LIBS) determination of fluorine concentration was investigated in detail. The measurements were realized on two double pulse LIBS devices featuring different parameters. Calibration curves, describing the relationship between the fluorine concentration and the corresponding intensity of the LIBS signal, were constructed for both LIBS devices, with and without He flow, respectively. Detection limits achieved were in the range 1.18-0.47wt.%. The best LOD value was obtained in He atmosphere. The LIBS measurement of fluorine content is influenced by different gate widths and the atmosphere in the working chamber. The proposed method was successfully applied to the determination of fluorine concentration in glass ionomer cements.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): T. Kratochvíl , M. Pouzar , K. Novotný , V. Havránek , T. Černohorský , M. Zvolská
The influence of He atmosphere and gate width in laser-induced breakdown spectroscopy (LIBS) determination of fluorine concentration was investigated in detail. The measurements were realized on two double pulse LIBS devices featuring different parameters. Calibration curves, describing the relationship between the fluorine concentration and the corresponding intensity of the LIBS signal, were constructed for both LIBS devices, with and without He flow, respectively. Detection limits achieved were in the range 1.18-0.47wt.%. The best LOD value was obtained in He atmosphere. The LIBS measurement of fluorine content is influenced by different gate widths and the atmosphere in the working chamber. The proposed method was successfully applied to the determination of fluorine concentration in glass ionomer cements.
Direct determination of bromine in plastic materials by means of solid sampling high-resolution continuum source graphite furnace molecular absorption spectrometry
16 September 2013,
08:53:11
Publication date: 1 October
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): M.R. Flórez , M. Resano
This work investigates the potential of high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of bromine in polymers, which could be interesting in view of the current regulations restricting the use of organobrominated compounds. The method developed is based on the addition of Ca (300μg) and Pd (30μg) to favor the formation of CaBr, which is monitored at the main molecular “lines” (rotational spectra) found in the vicinity of 625.315nm. It was found that accurate results could be obtained for all the samples investigated (polyethylene, polypropylene and acrylonitrile butadiene styrene certified reference materials) using any of the lines studied and constructing the calibration curve with aqueous standards. Furthermore, the combined use of the main four CaBr lines available in the spectral area simultaneously monitored permits to easily expand the linear range up to 2000ng, provides a limit of detection of 1.8ng (1.8μgg−1 for a mass of 1mg) and further improves precision to values between 3–7% RSD. Overall, the method proposed seems suited for the fast and simple control of these types of samples (approximately 10min for sample are required), circumventing the traditional problems associated with sample digestion (e.g., losses of volatile compounds), and providing sufficient sensitivity to easily comply with regulations.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): M.R. Flórez , M. Resano
This work investigates the potential of high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of bromine in polymers, which could be interesting in view of the current regulations restricting the use of organobrominated compounds. The method developed is based on the addition of Ca (300μg) and Pd (30μg) to favor the formation of CaBr, which is monitored at the main molecular “lines” (rotational spectra) found in the vicinity of 625.315nm. It was found that accurate results could be obtained for all the samples investigated (polyethylene, polypropylene and acrylonitrile butadiene styrene certified reference materials) using any of the lines studied and constructing the calibration curve with aqueous standards. Furthermore, the combined use of the main four CaBr lines available in the spectral area simultaneously monitored permits to easily expand the linear range up to 2000ng, provides a limit of detection of 1.8ng (1.8μgg−1 for a mass of 1mg) and further improves precision to values between 3–7% RSD. Overall, the method proposed seems suited for the fast and simple control of these types of samples (approximately 10min for sample are required), circumventing the traditional problems associated with sample digestion (e.g., losses of volatile compounds), and providing sufficient sensitivity to easily comply with regulations.
Signal enhancement in solution-cathode glow discharge — optical emission spectrometry via low molecular weight organic compounds
16 September 2013,
08:53:11
Publication date: 1 October
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): Todd A. Doroski , Michael R. Webb
HCOOH, CH3COOH, and CH3CH2OH were used as chemical modifiers in a solution-cathode glow discharge. Emission was measured directly from the discharge, without a gas–liquid separator or a secondary excitation source. Emission from Ag, Se, Pb, and Hg was strongly enhanced, and the detection limits (DL) for these elements were improved by up to an order of magnitude using a combination of HCOOH and HNO3 compared to using HNO3 alone. The DL was measured for Mg (1μg/L), Fe (10μg/L), Ni (6μg/L), Cu (6μg/L), Pb (1μg/L), Ag (0.1μg/L), Se (300μg/L), and Hg (2μg/L). Coefficients of determination (R2) were between 0.9986 and 0.9999. A voltage of 1kV was used, which produced a current of approximately 70mA.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): Todd A. Doroski , Michael R. Webb
HCOOH, CH3COOH, and CH3CH2OH were used as chemical modifiers in a solution-cathode glow discharge. Emission was measured directly from the discharge, without a gas–liquid separator or a secondary excitation source. Emission from Ag, Se, Pb, and Hg was strongly enhanced, and the detection limits (DL) for these elements were improved by up to an order of magnitude using a combination of HCOOH and HNO3 compared to using HNO3 alone. The DL was measured for Mg (1μg/L), Fe (10μg/L), Ni (6μg/L), Cu (6μg/L), Pb (1μg/L), Ag (0.1μg/L), Se (300μg/L), and Hg (2μg/L). Coefficients of determination (R2) were between 0.9986 and 0.9999. A voltage of 1kV was used, which produced a current of approximately 70mA.
Laser ablation molecular isotopic spectrometry of water for 1D2/1H1 ratio analysis
16 September 2013,
08:53:11
Publication date: 1 October
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): Arnab Sarkar , Xianglei Mao , George C.-Y. Chan , Richard E. Russo
Laser Ablation Molecular Isotopic Spectrometry (LAMIS) has been investigated for optical isotopic analysis of the deuterium to protium ratio in enriched water samples in ambient air at atmospheric pressure. Multivariate PLSR (Partial Least Squares Regression) based calibrations were carried out and validated using multiple statistical parameters. Comparisons of results are reported using two spectrometers having two orders of magnitude difference in spectral resolution. The accuracy and precision of isotopic analysis depends on the spectral resolution and the inherent isotope shift of the elements. The requirements for spectral resolution of the measurement system can be significantly relaxed when the isotopic abundance ratio is determined using chemometric processing of the spectra. Large isotopic shifts in the individual rotational branches of OH/OD molecular emission spectra were measured. Optimized temporal conditions for LAMIS measurements were established. Several sub-regions of spectra were used for PLSR calibration and the results demonstrate that both the emission intensity and degree of spectral differentiation affect the quality of the PLSR calibration. LAMIS results also were compared with traditional LIBS results obtained using PLSR and a spectral deconvolution method, demonstrating the advantages of LAMIS over LIBS with respect to isotopic composition determination.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): Arnab Sarkar , Xianglei Mao , George C.-Y. Chan , Richard E. Russo
Laser Ablation Molecular Isotopic Spectrometry (LAMIS) has been investigated for optical isotopic analysis of the deuterium to protium ratio in enriched water samples in ambient air at atmospheric pressure. Multivariate PLSR (Partial Least Squares Regression) based calibrations were carried out and validated using multiple statistical parameters. Comparisons of results are reported using two spectrometers having two orders of magnitude difference in spectral resolution. The accuracy and precision of isotopic analysis depends on the spectral resolution and the inherent isotope shift of the elements. The requirements for spectral resolution of the measurement system can be significantly relaxed when the isotopic abundance ratio is determined using chemometric processing of the spectra. Large isotopic shifts in the individual rotational branches of OH/OD molecular emission spectra were measured. Optimized temporal conditions for LAMIS measurements were established. Several sub-regions of spectra were used for PLSR calibration and the results demonstrate that both the emission intensity and degree of spectral differentiation affect the quality of the PLSR calibration. LAMIS results also were compared with traditional LIBS results obtained using PLSR and a spectral deconvolution method, demonstrating the advantages of LAMIS over LIBS with respect to isotopic composition determination.
Spectroscopic investigation of colliding plasma plumes
16 September 2013,
08:53:11
Publication date: 1 October
2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): Ravi Pratap Singh , Shyam L. Gupta , R.K. Thareja
Time-resolved and space-resolved spectroscopic and imaging studies of colliding carbon plumes are reported, with the aim of understanding the dynamics of the ablated plume in comparison to single-plume carbon plasma. Laser produced colliding plumes and single plume were studied under vacuum (of the order 5×10−5 mbar) in a nitrogen environment using a flat graphite target. Due to the interaction of energetic particles of two colliding plumes, a new particle layer is formed that stagnate for a longer time than the seed plasma. Variation of the plume front and dimension of the stagnation layer with time are also reported.
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 88
Author(s): Ravi Pratap Singh , Shyam L. Gupta , R.K. Thareja
Time-resolved and space-resolved spectroscopic and imaging studies of colliding carbon plumes are reported, with the aim of understanding the dynamics of the ablated plume in comparison to single-plume carbon plasma. Laser produced colliding plumes and single plume were studied under vacuum (of the order 5×10−5 mbar) in a nitrogen environment using a flat graphite target. Due to the interaction of energetic particles of two colliding plumes, a new particle layer is formed that stagnate for a longer time than the seed plasma. Variation of the plume front and dimension of the stagnation layer with time are also reported.
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