Calibration graphs for Ti, Ta and Nb in sintered tungsten carbide by infrared laser ablation inductively coupled plasma atomic emission spectrometry

Infrared laser ablation (IR-LA) has been studied as a sample introduction technique for the analysis of sintered cobalt-cemented tungsten carbide materials by inductively coupled plasma atomic emission spectrometry (ICP-AES). Fractionation of cobalt was observed. Linearity of calibration plots was verified at least up to 15% Ti, 8% Ta, and 3% Nb. Above 1% (m/m) Ti, Ta, and Nb, the repeatability of results was better than 3% R.S.D. The relative uncertainty at the centroid of the calibration line was in the range from +/- 3% to +/- 4% for Ti, Ta, and Nb with internal standardization by tungsten and up to +/- 5% without internal standardization. The limits of detection were 0.004% Ti, 0.001% Ta, and 0.004% Nb. Elimination of the cemented hardmetal dissolution procedure is the main advantage of this method.     

Influence of binders on infrared laser ablation of powdered tungsten carbide pressed pellets in comparison with sintered tungsten carbide hardmetals studied by inductively coupled plasma atomic emission spectrometry

Laser ablation (LA) was studied as a sample introduction technique for the analysis of powdered and sintered tungsten carbides (WC/Co) by inductively coupled plasma optical emission spectrometry (ICP–OES). The possibility to work with powdered and compact materials with close chemical composition provided the opportunity to compare LA sampling of similar substances in different forms that require different preparation procedures. Powdered WC/Co precursors of sintered hardmetals were prepared for the ablation as pressed pellets with and without powdered silver as a binder, while sintered hardmetal blocks were embedded into a resin to obtain discs, which were then smoothed and polished. A Q-switched Nd:YAG laser operated at its fundamental wavelength of 1064 nm with a pulse frequency of 10 Hz and maximum pulse energy of 220 mJ was used. A single lens was used for the laser beam focusing. An ablation cell (14 cm³) mounted on a PC-controlled XY-translator was connected to an ICP spectrometer Jobin Yvon 170 Ultrace (laterally viewed ICP, mono- and polychromator) using a 1.5-m tubing (4 mm i.d.). Ablation was performed in a circular motion (2 mm diameter). Close attention was paid to the study of the crater parametres depending on hardness, cohesion and Ag binder presence in WC/Co samples. The influence of the Co content on the depth and structure of the ablation craters of the binderless pellets was also studied. Linear calibration plots of Nb, Ta and Ti were obtained for cemented WC/Co samples, binderless and binder-containing pellets. Relative widths of uncertainty intervals about the centroids vary between ± 3% and ± 7%, and exceptionally reach a value above 10%. The lowest determinable quantities (LDQ) of Nb, Ta and Ti calculated from the calibration lines were less than 0.5% (m/m). To evaluate the possibility of quantitative elemental analysis by LA–ICP–OES, two real sintered WC/Co samples and two real samples of powdered WC/Co materials were analysed. The results of LA–ICP–OES real sample analysis correlated well with the results obtained by X-ray fluorescence (sintered samples) and pneumatic nebulization inductively coupled plasma optimal emmission spectrometry (powdered samples) with a bias not exceeding 6.5%.     

Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials

A study of LA-ICP-MS analysis of pressed powdered tungsten carbide precursors was performed to show the advantages and problems of nanosecond laser ablation of matrix-unified samples. Five samples with different compositions were pressed into pellets both with silver powder as a binder serving to keep the matrix unified, and without any binder. The laser ablation was performed by nanosecond Nd:YAG laser working at 213 nm.The particle formation during ablation of both sets of pellets was studied using an optical aerosol spectrometer allowing the measurement of particle concentration in two size ranges (10-250 nm and 0.25-17 μm) and particle size distribution in the range of 0.25-17 μm. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using a scanning electron microscope (SEM) and the particle chemical composition was determined by an energy dispersive X-ray spectroscope (EDS).The matrix effect was proved to be reduced using the same silver powdered binder for pellet preparation in the case of the laser ablation of powdered materials.The LA-ICP-MS signal dependence on the element content present in the material showed an improved correlation for Co, Ti, Ta and Nb of the matrix-unified samples compared to the non-matrix-unified pellets. In the case of W, the ICP-MS signal of matrix-unified pellets was influenced by the changes in the particle formation.     

Analysis of powdered tungsten carbide hard-metal precursors and cemented compact tungsten carbides using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been applied to the direct analysis of powdered tungsten carbide hard-metal precursors and cemented tungsten carbides. The aim of this work was to examine the possibility of quantitative determination of the niobium, titanium, tantalum and cobalt. The investigated samples were in the form of pellets, pressed with and without binder (powdered silver) and in the form of cemented tungsten carbides. The pellets were prepared by pressing the powdered material in a hydraulic press. Cemented tungsten carbides were embedded in resin for easier manipulation.

Several lasers and detection systems were utilized. The Nd:YAG laser working at a basic wavelength of 1064 nm and fourth-harmonic frequency of 266 nm with a gated photomultiplier or ICCD detector HORIBA JY was used for the determination of niobium which was chosen as a model element. Different types of surrounding gases (air, He, Ar) were investigated for analysis. The ICCD detector DICAM PRO with Mechelle 7500 spectrometer with ArF laser (193 nm) and KrF laser (248 nm) were employed for the determination of niobium, titanium, tantalum and cobalt in samples under air atmosphere. Good calibration curves were obtained for Nb, Ti, and Ta (coefficients of determination r² > 0.96). Acceptable calibration curves were acquired for the determination of cobalt (coefficient of determination r² = 0.7994) but only for the cemented samples. In the case of powdered carbide precursors, the calibration for cobalt was found to be problematic.     

Calibration graphs for steels by IR laser ablation inductively coupled plasma atomic emission spectrometry

Infrared laser ablation (IRLA) was studied as a sample-introduction technique for the analysis of steels by inductively coupled plasma atomic emission spectrometry (ICP-AES). A comparison of two IRLA-ICP-AES systems based on Q-switched nanosecond Nd: YAG lasers was performed. The beam of the LINA-Spark atomizer (LSA Sarl, Cully, Switzerland) based on the Surelite 1-20 laser (Continuum, USA) was moved along a circle. A Perkin-Elmer Optima 3000 DV ICP system was used both with lateral and axial viewing modes. A laboratory-made ablation system based on the Brilliant laser (Quantel) was coupled to a Jobin-Yvon 170 Ultrace ICP (lateral viewing, polychromator part employed). A sample was rotated along a circle during ablation. Linearity of calibration plots was verified at least up to 19% Cr and 12% Ni without internal standardization for both LA-ICP-AES systems. Other elements examined were Mo up to 3%, Mn up 1.5%, Si up to 1.7%, and Cu up to 0.15%. The reproducibility was in the range 5-1 %RSD for a mass percentage 0.5-20% of steel constituents. The relative uncertainty of the centroids of the calibration lines was in the range from +/- 4% to +/- 12% for Cr, Ni, Mn, Mo, and Si, and from +/- 8% to +/- 19% for Cu. The lowest determinable quantities were calculated for calibration dependencies. Performances of both the IR-LA-ICP-AES were comparable.     

Infrared laser ablation study of pressed soil pellets with inductively coupled plasma atomic emission spectrometry

Potential of infrared laser ablation (LA) coupled with ICP-AES as a technique suitable for the determination of trace elements (Zn, Cu, Ni, Cr, and V) in agricultural soils was studied. Operating parameters such as laser beam energy, laser beam focusing with respect to the sample surface, and velocity of the sample translation in the plane perpendicular to the laser beam were optimized. Soil samples were mixed with powdered Ag as a binder, and an internal standard (GeO(2)), and pressed into pellets. Calibration samples were prepared by adding known amounts of oxides of elements of interest into soils of known elemental composition and then processed in the same way as the analyzed samples. Calibration curves were found to be linear at least up to several hundreds of mg kg(-1) for the elements of interest. The elemental contents obtained by using LA-ICP-AES were compared with those obtained by analysis using wet chemistry followed by ICP-AES with pneumatic nebulization (PN). The results were in good agreement. Accuracy was also tested using certified reference soils with a bias not exceeding 10% relative.     

Determination of additives in PVC material by UV laser ablation inductively coupled plasma atomic emission spectrometry

UV laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) has been applied to the direct determination of additives in solid poly(vinyl chloride) materials. A Nd:YAG laser, operating at its fourth harmonic (266 nm), was used with a beam masking device, in the most reproducible conditions, to introduce solid particles into the plasma torch of a simultaneous ICP-AES system. Emphasis was placed on both precision and accuracy in the analysis of PVC materials by LA-ICP-AES. A series of six in-house PVC reference materials was prepared by incorporating several additives in increasing concentrations. Three alternative methods were evaluated to certify the amount of incorporated elements: ICP-AES with sample dissolution, NAA and XRF. Satisfactory results and good agreement were obtained for seven elements (Al, Ca, Cd, Mg, Sb, Sn and Ti) among the ten incorporated. Sample homogeneity appeared to be satisfactory, and calibration graphs obtained by LA-ICP-AES for several elements are presented. Finally, the performance of the technique in terms of repeatability (1.6-5%), reproducibility (2–5%), and limits of detection was investigated.     

Laser defocusing effects on laser ablation inductively coupled plasma-atomic emission spectrometry: different ablation interactions between the laser and low-alloy steel, Fe pellets, and a pond sediment pellet.

The ablation interaction between a laser and solid samples, which affects the analytical performance for laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES), was studied. The emission intensities of elements observed by LA-ICP-AES (LA-ICP-AES element signal intensities) for different solid samples were measured under different laser defocusing conditions with a fixed laser output energy. It was found that the optimum laser defocusing conditions were dependent on the different solid samples with different sample characteristics, and also on the different elements with different elemental characteristics in each solid sample. A low-alloy steel, pellets containing different Fe concentrations (0 - 100% Fe pellet), and a pond sediment pellet were used as different solid samples. The variations of the LA-ICP-AES Fe signal intensities observed under different laser defocus conditions were completely different between the low-alloy steel and the pond sediment pellet. The changes in the LA-ICP-AES Fe signal intensities for 90 and 100% Fe pellets were similar to that of the low-alloy steel. However, pellets with lower Fe concentrations (less than 70%) showed different trends and the defocusing behavior became closer to that of the pond sediment pellet. The LA-ICP-AES signal intensities of other elements were also evaluated, and were compared for different solid samples and different defocusing behavior. It was observed that the changes in the LA-ICP-AES signal intensities of almost all elements in the pond sediment pellet showed a similar trend to those of Fe for different laser defocus positions; that is, the elemental fractionation for these elements in the pond sediment pellet seemed to be relatively small. On the contrary, it was found that the LA-ICP-AES Si, Ti, and Zr signal intensities for low-alloy steel showed different trends compared to those of other elements, including Fe, under different defocusing conditions; that is, the elemental fractionation observed for the low-alloy steel was larger than that of the pond sediment pellet. From these results, different ablation interactions between the laser and the different solid samples were considered, and attributed to the sample characteristics, such as the matrix, hardness, and conductivity. Elemental fractionation was attempted to be explained by using elemental characteristics, such as the melting point and ionization energy of the elements.     

Determination of trace elements in zeolites by laser ablation ICP-MS

Laser ablation inductively coupled plasma mass spectrometry using a quadrupole-based mass spectrometer (LA-ICP-QMS) was applied for the analysis of powdered zeolites (microporous aluminosilicates) used for clean-up procedures. For the quantitative determination of trace element concentrations three geological reference materials, granite NIM-G, lujavrite NIM-L and syenite NIM-S, from the National Institute for Metallurgy (South Africa) with a matrix composition corresponding to the zeolites were employed. Both the zeolites and reference materials were fused with a lithium borate mixture to increase the homogeneity and to eliminate mineralogical effects. In order to compare two different approaches for the quantification of analytical results in LA-ICP-MS relative sensitivity coefficients (RSCs) of chemical elements and calibration curves were measured using the geostandards. The experimentally obtained RSCs are in the range of 0.2-6 for all elements of interest. Calibration curves for trace elements were measured without and with Li or Ti as internal standard element. With a few exceptions the regression coefficients of the calibration curves are better than 0.993 with internal standardization. NIM-G granite reference material was employed to evaluate the accuracy of the technique. Therefore, the measured concentrations were corrected with RSCs which were determined using lujavrite reference material NIM-L. This quantification method provided analytical results with deviations of 1–11% from the recommended and proposed values in granite reference material NIM-G, except for Co, Cs, La and Tb. The relative standard deviation (RSD) of the determination of the trace element concentration (n = 5) is about 1% to 6% using Ti as internal standard element. Detection limits of LA-ICP-QMS in the lower μg/g range (from 0.03 μg/g for Lu, Ta and Th to 7.3 μg/g for Cu, with the exception of La) have been achieved for all elements of interest. Under the laser ablation conditions employed (λ: 266 nm, repetition frequency: 10 Hz, pulse energy: 10 mJ, laser power density: 6 × 10⁹ W/cm²) fractionation effects of the determined elements relative to the internal standard element Ti were not observed. Received: 7 April 2000 / Revised: 25 May 2000 / Accepted: 31 May 2000     

Analysis of the spatial distribution of the constituting elements in amorphous solids: Laser ablation with ICP spectrometry

Amorphous materials of the systems Si/B/N/C and Ba/Si/Al/O/C, which are highly resistant against thermal and chemical attack, were analyzed using laser ablation inductively coupled plasma atomic emission (LA-ICP-AES) and mass spectrometry (MS) in order to prove the applicability of these techniques to this special type of materials. Homogeneity was evaluated and the concentrations of the main components were determined with a resolution of 50 μm. A good reproducibility was obtained using one element for internal standardization (0.3–0.7% RSD for Si and Al with Ba as internal standard and about 1.5% for B with Si as internal standard). Scanning white light interferometry employed for the measuring of the crater volumes was tested to support the internal standardization method. Received: 13 May 1998 / Revised: 6 July 1998 / Accepted: 10 July 1998     

Analysis of the spatial distribution of the constituting elements in amorphous solids: Laser ablation with ICP spectrometry

Amorphous materials of the systems Si/B/N/C and Ba/Si/Al/O/C, which are highly resistant against thermal and chemical attack, were analyzed using laser ablation inductively coupled plasma atomic emission (LA-ICP-AES) and mass spectrometry (MS) in order to prove the applicability of these techniques to this special type of materials. Homogeneity was evaluated and the concentrations of the main components were determined with a resolution of 50 μm. A good reproducibility was obtained using one element for internal standardization (0.3–0.7% RSD for Si and Al with Ba as internal standard and about 1.5% for B with Si as internal standard). Scanning white light interferometry employed for the measuring of the crater volumes was tested to support the internal standardization method. Received: 13 May 1998 / Revised: 6 July 1998 / Accepted: 10 July 1998     

Determination of trace elements in zeolites by laser ablation ICP-MS

Laser ablation inductively coupled plasma mass spectrometry using a quadrupole-based mass spectrometer (LA-ICP-QMS) was applied for the analysis of powdered zeolites (microporous aluminosilicates) used for clean-up procedures. For the quantitative determination of trace element concentrations three geological reference materials, granite NIM-G, lujavrite NIM-L and syenite NIM-S, from the National Institute for Metallurgy (South Africa) with a matrix composition corresponding to the zeolites were employed. Both the zeolites and reference materials were fused with a lithium borate mixture to increase the homogeneity and to eliminate mineralogical effects. In order to compare two different approaches for the quantification of analytical results in LA-ICP-MS relative sensitivity coefficients (RSCs) of chemical elements and calibration curves were measured using the geostandards. The experimentally obtained RSCs are in the range of 0.2-6 for all elements of interest. Calibration curves for trace elements were measured without and with Li or Ti as internal standard element. With a few exceptions the regression coefficients of the calibration curves are better than 0.993 with internal standardization. NIM-G granite reference material was employed to evaluate the accuracy of the technique. Therefore, the measured concentrations were corrected with RSCs which were determined using lujavrite reference material NIM-L. This quantification method provided analytical results with deviations of 1-11% from the recommended and proposed values in granite reference material NIM-G, except for Co, Cs, La and Tb. The relative standard deviation (RSD) of the determination of the trace element concentration (n = 5) is about 1% to 6% using Ti as internal standard element. Detection limits of LA-ICP-QMS in the lower microg/g range (from 0.03 microg/g for Lu, Ta and Th to 7.3 microg/g for Cu, with the exception of La) have been achieved for all elements of interest. Under the laser ablation conditions employed (lambda: 266 nm, repetition frequency: 10 Hz, pulse energy: 10 mJ, laser power density: 6 x 10(9) W/cm2) fractionation effects of the determined elements relative to the internal standard element Ti were not observed.     

Use of a single calibration graph for the determination of major elements in geological materials by laser ablation inductively coupled plasma atomic emission spectrometry with added internal standards

The possibility of internal standardisation in laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) of geological materials by added Sc₂O₃ and Y₂O₃ has been examined to cover the wide range of concentrations of major and minor constituents both in silicate rocks and limestones. A Nd : YAG laser (355 nm, 10 Hz, 10 mJ per shot) was used for the ablation of discs obtained by fusion of the mixture of samples and oxides of Sc and Y with lithium tetraborate. The flux/sample ratio was in the range from 6 to 10. The contents of analytes were within the concentration range from hundredths to tens of percentage. The trace elements copper and nickel were studied, too. An ICP emission spectrometer OPTIMA 3000 DV was used for the measurement of Si, Al, Ca, Mg, Sr, Ba, Fe, Ti, Mn, Ni, Cu, Na and K analyte lines and Y and Sc reference lines in the axial observation mode. The long-term and the short-term repeatability of measurement were improved by employing scandium or yttrium internal references lines for the above analytes from 6% to 1.5% of RSD and from 2.4% to 1.0% of RSD, respectively. The correlation of signals with concentrations was improved in terms of the correlation coefficient r from 0.90–0.97 to 0.98–0.998 and the relative uncertainity on the centroid of concentrations was improved 2–3 times. A single calibration graph covering the concentration range both in silicates and carbonates is possible for each of elements, as the matrix effects are compensated for by internal standards and the excess of Li₂B₄O₇. Received: 20 June 1998 / Revised: 20 July 1998 / Accepted: 21 September 1998     

Determination of tungsten in niobium-tantalum, vanadium and molybdenum bearing geological samples using derivative spectrophotometry and ICP-AES

Two different procedures, one using derivative spectrophotometry and another using inductively coupled plasma atomic emission spectrometry (ICP-AES) have been developed for the determination of tungsten in niobate-tantalates, tin slag samples, ores, concentrates and vanadium and molybdenum bearing geological materials. In the first method involving derivative spectrophotometry, 0.05-0.5 g of the sample is fused with sodium hydroxide, the tungsten is extracted by leaching the melt with distilled water and estimated as thiocyanate using a second derivative spectrophotometric method in the presence of interferents, i.e. Nb, Mo and V, without separating them. Mixtures of tungsten with V, Nb and Mo are used for standardizing the various parameters like zero-crossing wavelength, wavelength range, etc. Tolerance limits for V, Nb and Mo have also been evaluated. In the second method involving ICP-AES, 0.05-0.5 g of sample is fused with KHSO(4) to a clear melt and dissolved in ammonium oxalate solution. Ammonium hydroxide precipitation is then carried out to separate Nb and Ta as hydroxides and the filtrate is boiled with nitric acid to destroy the oxalates before aspiration into the plasma for measurement of tungsten values by ICP-AES using the 207.911 nm emission line. Both methods have been applied to niobate-tantalate and tin slag samples and the results obtained are reported in this paper. The values obtained by both methods are in good agreement with each other. The proposed methods have also been applied to the determination of tungsten in two Canadian Certified Reference Standards (CT-1 and MP-2) and the values obtained are in good agreement with the certified values and the R.S.D.% in case of the ICP-AES method varied from 1-2% at >1000 mug g(-1) level to 9.4% at the 20 mug g(-1) level whereas the R.S.D.% in case of the derivative method varied from 1 to 7.8%.     

Use of a single calibration graph for the determination of major elements in geological materials by laser ablation inductively coupled plasma atomic emission spectrometry with added internal standards

The possibility of internal standardisation in laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) of geological materials by added Sc₂O₃ and Y₂O₃ has been examined to cover the wide range of concentrations of major and minor constituents both in silicate rocks and limestones. A Nd?:?YAG laser (355 nm, 10 Hz, 10 mJ per shot) was used for the ablation of discs obtained by fusion of the mixture of samples and oxides of Sc and Y with lithium tetraborate. The flux/sample ratio was in the range from 6 to 10. The contents of analytes were within the concentration range from hundredths to tens of percentage. The trace elements copper and nickel were studied, too. An ICP emission spectrometer OPTIMA 3000 DV was used for the measurement of Si, Al, Ca, Mg, Sr, Ba, Fe, Ti, Mn, Ni, Cu, Na and K analyte lines and Y and Sc reference lines in the axial observation mode. The long-term and the short-term repeatability of measurement were improved by employing scandium or yttrium internal references lines for the above analytes from 6% to 1.5% of RSD and from 2.4% to 1.0% of RSD, respectively. The correlation of signals with concentrations was improved in terms of the correlation coefficient r from 0.90–0.97 to 0.98–0.998 and the relative uncertainity on the centroid of concentrations was improved 2–3 times. A single calibration graph covering the concentration range both in silicates and carbonates is possible for each of elements, as the matrix effects are compensated for by internal standards and the excess of Li₂B₄O₇.     

Determination of vanadium and titanium in steel by inductively coupled plasma atomic emission spectrometry with modified use of a tungsten boat furnace atomizer for atomic absorption spectrometry

For electrothermal sample introduction, a commercially available tungsten boat atomizer for atomic absorption spectrometry (AAS) was transferred to a vaporizer for inductively coupled plasma atomic emission spectrometry (ICP-AES). The modification retained as much of the original design of the atomizer as possible, so that the apparatus could be switched easily between conventional tungsten boat furnace (TBF)-AAS and TBF-ICP-AES. By using this system, a procedure for the determination of vanadium and titanium in steel was investigated. The detection limits (S/N=3) of vanadium and titanium were 3.9 and 1.5 ng ml^?1, respectively. The relative standard deviations for five replicate determinations were ca. 3% for both elements. The calibration graphs were linear up to 100 μg ml^?1 vanadium(V) and 10 μg ml^?1 titanium(IV). Results of analyses of some low-alloy steel samples are given.     

Room temperature acid sonication ICP-MS multielemental analysis of milk

Room temperature acid sonication of milk samples is proposed as a fast alternative methodology for the determination of the total content of 45 elements (Li, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Mo, Ag, Cd, In, Sn, U, Sb, Te, Cs, Ba, Hg, Pb, Bi, Th, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Hf and Ta) in milk by inductively coupled plasma mass spectrometry (ICP-MS). The aforementioned procedure involves a 10 min sample pre-treatment. Measurements were made in quantitative and semiquantitative (Totalquant^®) modes of analysis using Rh as internal standard and Be, Ge, Tb and Re for internal calibration of the equipment in the semiquantitative mode. The selected isotopes were in general the most abundant ones of each element, except in cases where polyatomic or isobaric interferences were detected. Results of total concentrations in 10 liquid and 11 powdered commercially available milk samples were presented. Method validation was performed by measuring a SRM NIST-1549 non-fat milk powder and through the use of recovery experiments. Additionally, the proposed methodology was compared with a method based on a previous microwave-assisted digestion of samples and a direct analysis of 1:4 diluted samples.     

Selection of internal standards for analysis of silicate rocks and limestones by laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES)

Included (Si, Ca) and added (Li, B) internal standards (IS) have been used comparatively in LA-ICP-AES of silicates and limestones to improve both precision and accuracy. A Q-switched Nd:YAG laser (355 nm, 10 Hz, 10 mJ per shot) has been applied for ablation. Samples have been prepared by fusion with Li₂B₄O₇ and measured using a Perkin-Elmer Optima 3000 ICP system. Both types of IS have given a relative standard deviation (RSD) less than 2–1%, which improved the repeatability by a factor of 2–10 and calibration graphs have been linear over the whole concentration range.     

Calibration graphs for steels by IR laser ablation inductively coupled plasma atomic emission spectrometry

Infrared laser ablation (IRLA) was studied as a sample-introduction technique for the analysis of steels by inductively coupled plasma atomic emission spectrometry (ICP–AES). A comparison of two IRLA–ICP–AES systems based on Q-switched nanosecond Nd?:?YAG lasers was performed. The beam of the Lina-Spark atomizer (LSA Sarl, Cully, Switzerland) based on the Surelite I-20 laser (Continuum, USA) was moved along a circle. A Perkin–Elmer Optima 3000 DV ICP system was used both with lateral and axial viewing modes. A laboratory-made ablation system based on the Brilliant laser (Quantel) was coupled to a Jobin-Yvon 170 Ultrace ICP (lateral viewing, polychromator part employed). A sample was rotated along a circle during ablation. Linearity of calibration plots was verified at least up to 19% Cr and 12% Ni without internal standardization for both LA–ICP–AES systems. Other elements examined were Mo up to 3%, Mn up 1.5%, Si up to 1.7%, and Cu up to 0.15%. The reproducibility was in the range 5–1 %RSD for a mass percentage 0.5–20% of steel constituents. The relative uncertainty of the centroids of the calibration lines was in the range from ± 4% to ± 12% for Cr, Ni, Mn, Mo, and Si, and from ± 8% to ± 19% for Cu. The lowest determinable quantities were calculated for calibration dependencies. Performances of both the IR-LA–ICP–AES were comparable.     

Studies on laser defocusing effects on laser ablation inductively coupled plasma-atomic emission spectrometry using emission signals from a laser-induced plasma

The effect of laser defocusing on analytical performance of laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) was studied by varying laser focus conditions with respect to the surface of a low-alloy steel and a powdered sediment pellet. Laser-induced plasma (LIP) and LA-ICP-AES emission signals and LIP excitation temperatures (LIP T_ex) were determined and compared for different laser defocus conditions. LIP Fe and LA-ICP-AES Fe emission signals and LIP T_ex decreased when the laser was defocused for the low-alloy steel. On the other hand, when the sediment pellet was ablated, LIP T_ex decreased when the laser was defocused. However, LA-ICP-AES Fe emission signals increased at first, then decreased when the laser was defocused more. It was concluded that LIP T_ex and LIP and LA-ICP-AES Fe emission signals are dependent on laser shot conditions (focus–defocus), and are also dependent on sample type (texture, mineralogy, hardness, conductivity and heat capacity).