Improvements in calibration procedures for the quantitative determination of trace elements in carbonate material (mussel shells) by laser ablation ICP-MS

A better repeatability and accuracy in the quantitative determination of trace elements in mussel shells or carbonate-based materials by LA-ICP-MS was achieved by using a series of multielement calibration standards prepared by co-precipitation of twelve elements into a CaCO₃ matrix in order to improve the homogeneity of the resulting powder samples. Pressed powder discs of good mechanical stability could be obtained at a pressure of 50 MPa, without the addition of a binder. An UV laser (modified Nd:YAG, 266 nm) was used in the Q-switched mode at a repetition rate of 10 Hz and an energy level of 3.5 mJ. Correlation coefficients (R) for the linear calibration graphs (concentration range: 1.5–400 μg/g) for Cr, Mn, Co, Cu, Zn, As, Cd, Sn, Ba, and Pb are generally better than 0.997. The detection limits for all elements investigated are in the sub-μg/g range. Incorporation of elements into the matrix by co-precipitation has shown as a superior method for producing calibration standards than the simple mixture of the analytes (in carbonate or oxide form) with the matrix (CaCO₃) or addition of standard solutions to a carbonate powder base. Two examples of the quantitative determination of toxic elements in mussel shells will be presented. Received: 10 January 2000 / Revised: 16 March 2000 / Accepted: 26 March 2000     

Matrix-matched quantitative analysis of trace-elements in calcium carbonate shells by laser-ablation ICP–MS: application to the determination of daily scale profiles in scallop shell (<Emphasis Type="Italic">Pecten maximus</Emphasis>)

A micro-scale method has been developed for analysis of trace-element concentration profiles in the calcium carbonate shell of the Great Scallop (Pecten maximus). UV laser ablation at 266-nm coupled with ICP–MS detection was used to analyse daily calcite striae of shell samples to obtain high temporal resolution of trace element incorporation. Analysis of scallop shells was carefully examined to determine the quality of calcium carbonate ablation and calibration. An accurate external calibration method based on matrix matching was developed. Twelve sodium-free enriched calcium carbonate standards containing up to twenty-four elements were prepared, by co-precipitation with aqueous ammonia and NH₄HCO₃, and subsequently back-calibrated in the laboratory. These CaCO₃ standards were found to be homogenous and their use enabled sensitive quantitative analysis (detection limits of a few ng g⁻¹) over a wide range of concentrations (0.1 to 500 μg g⁻¹). Use of these CaCO₃ standards was also evaluated by analysis of three calcium-rich certified reference materials. Because calibration was consistent with the certified results, this analytical method is a sensitive tool for analysis of environmental calcium carbonate matrices. Repeated analysis of scallop shell samples collected simultaneously at the same location showed that the trace elements are homogeneously distributed along a stria. The reliability of such in-situ records of biogenic calcium carbonate (scallop shells) is apparent from the inter-individual and inter-annual reproducibility of the trace element profiles.     

Trace analysis of high-purity graphite by LA-ICP-MS

Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been established as a very efficient and sensitive technique for the direct analysis of solids. In this work the capability of LA-ICP-MS was investigated for determination of trace elements in high-purity graphite. Synthetic laboratory standards with a graphite matrix were prepared for the purpose of quantifying the analytical results. Doped trace elements, concentration 0.5 microg g(-1), in a laboratory standard were determined with an accuracy of 1% to +/- 7% and a relative standard deviation (RSD) of 2-13%. Solution-based calibration was also used for quantitative analysis of high-purity graphite. It was found that such calibration led to analytical results for trace-element determination in graphite with accuracy similar to that obtained by use of synthetic laboratory standards for quantification of analytical results. Results from quantitative determination of trace impurities in a real reactor-graphite sample, using both quantification approaches, were in good agreement. Detection limits for all elements of interest were determined in the low ng g(-1) concentration range. Improvement of detection limits by a factor of 10 was achieved for analyses of high-purity graphite with LA-ICP-MS under wet plasma conditions, because the lower background signal and increased element sensitivity.     

Trace metals in mussel shells and corresponding soft tissue samples: a validation experiment for the use of <Emphasis Type="Italic">Perna perna</Emphasis> shells in pollution monitoring

The uptake of Cr, Mn, Ni, Cu, Zn, Cd and Pb in soft tissue of Perna perna mussels and their shells has been studied in aquarium experiments in which mussels were exposed for 30 or 60 days to seawater spiked with different concentrations of these contaminants (125 and 500 μg L⁻¹). Tissue samples were analyzed after acid digestion by conventional solution nebulization ICP–MS. Laser ablation ICP–MS was used for the quantitative determination of trace elements in different areas of the corresponding shells. With the exception of Mn and Zn, all other elements studied showed a significant concentration enhancements in soft tissue, with the magnitude of this enhancement following the order: Cr > Ni > Cd > Cu > Pb. A corresponding increase in most contaminants, although less pronounced, was also observed in the newly formed growth rings of mussel shells, contributing to the validation of Perna perna mussel shell as a bioindicator of toxic elements.     

Determination of Platinum Group Elements in Sulfide-Containing Minerals by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry with Synthetic Calibration Standards

This paper develops sulfide calibration standards for quantitative determination of platinum group elements in natural sulfide-containing minerals by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). A series of sulfide calibration standards containing different concentrations of platinum group elements were prepared using a home-made high temperature furnace. Homogeneity of element distribution expressed as the RSD of signal intensity were less than 10%. The effective concentrations of platinum group elements in synthetic calibration standards were obtained both by pneumatic nebulization ICP-MS and by LA-ICP-MS. Relative percentage differences of these results obtained by two methods were mainly less than 11%. The synthetic calibration standards were then employed as calibrators for quantitative determination of platinum group elements in two natural chalcopyrite samples. The valid results demonstrated that our synthetic standards could be considered for quantitative microanalysis of platinum group elements in natural sulfide-containing minerals.     

The Determination of Trace Elements by Solid State Luminescence

Abstract

Phosphor luminescence, resulting from the incorporation of trace metal ions into a solid state crystal lattice, has been applied to the quantitative determination of lead and bismuth. The relative fluorescence intensity is linear for 15 to 100 ng of bismuth per spot on calcium carbonate. Lead(II), preconcentrated by co-precipitation with calcium oxalate, can be determined at the ng per ml level by measurement of luminescence after ignition of oxalate to oxide; results are reproducible and the calibration curve is linear up to 15 μg of lead per 100 mg of calcium oxalate precipitate.     

Application of RF GDMS for trace element analysis of nonconducting La0.65Sr0.3MnO3 ceramic layers

Radio-frequency glow discharge mass spectrometry (RF GDMS) has been applied to the determination of trace elements in ceramic perovskite layers (La_0.65Sr_0.3MnO₃) using synthetic standards. For the preparation of these standards high-purity powder of the basic material (La_0.65Sr_0.3MnO₃) was doped with trace elements in concentrations from 20 to 500 μg/g and the mixture was pressed to compact samples. The resulting calibration curves and the calculated relative sensitivity factors (RSF) differed only from 0.4 to 2 for different elements. For nearly all elements the standard deviations in the determination of trace elements in La_0.65Sr_0.3MnO₃ were better than 15% and detection limits (using the 3σ-criterion) were below 10 μg/g. Changes of the discharge parameters (RF power, pressure of the discharge gas (Ar) in the RF glow discharge) have no significant influence on the sensitivity to elements.     

Trace analysis of high-purity graphite by LA–ICP–MS

Laser-ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) has been established as a very efficient and sensitive technique for the direct analysis of solids. In this work the capability of LA–ICP–MS was investigated for determination of trace elements in high-purity graphite. Synthetic laboratory standards with a graphite matrix were prepared for the purpose of quantifying the analytical results. Doped trace elements, concentration 0.5 μg g^–1, in a laboratory standard were determined with an accuracy of 1% to ± 7% and a relative standard deviation (RSD) of 2–13%. Solution-based calibration was also used for quantitative analysis of high-purity graphite. It was found that such calibration led to analytical results for trace-element determination in graphite with accuracy similar to that obtained by use of synthetic laboratory standards for quantification of analytical results. Results from quantitative determination of trace impurities in a real reactor-graphite sample, using both quantification approaches, were in good agreement. Detection limits for all elements of interest were determined in the low ng g^–1 concentration range. Improvement of detection limits by a factor of 10 was achieved for analyses of high-purity graphite with LA–ICP–MS under wet plasma conditions, because the lower background signal and increased element sensitivity. Received: 4 January 2001 / Revised: 27 March 2001 / Accepted: 28 March 2001     

Determination of minor elements in steelmaking flue dusts using laser ablation inductively coupled plasma mass spectrometry

Element determination in solid waste products from the steel industry usually involves the time-consuming step of preparing a solution of the solid. Laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to the analysis of Cr, Ni, Cu, As, Cd and Sn, elements of importance from the point of view of their impact on the environment, in electric arc furnace flue dust (EAFD). A simple method of sample preparation as pressed pellets using a mixture of cellulose and paraffin as binder material was applied. Calibration standards were prepared spiking multielement solution standards to a 1:1 ZnO + Fe₂O₃ synthetic matrix. The wet powder was dried and mechanically homogenised. Quantitative analysis were based on external calibration using a set of matrix matched calibration standards with Rh as a internal standard. Results obtained using only one-point for calibration without matrix matched, needing less time for standardization and data processing, are also presented. Data are calculated for flue dust reference materials: CRM 876-1 (EAFD), AG-6203 (EAFD), AG-6201 (cupola dust) and AG-SX3705 (coke ashes), and for two representative electrical arc furnace flue dusts samples from Spanish steelmaking companies: MS-1 and MS-2. For the reference materials, an acceptable agreement with certificate values was achieved, and the results for the MS samples matched with those obtained from conventional nebulization solutions (CN). The analytical precision was found to be better than 7% R.S.D. both within a single pellet and between several pellets of the same sample for all the elements.     

聚对苯二甲酸乙二醇酯/碳酸钙纳米复合材料的制备和表征

以聚乙二醇磷酸酯1000为表面处理剂, 采用碳化法合成了方解石型碳酸钙纳米粒子, 进一步制备了聚对苯二甲酸乙二醇酯/碳酸钙纳米复合材料. 采用透射电子显微镜(TEM)、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR), 场发射扫描电子显微镜(FESEM)和热重分析(TGA)对样品进行了分析. 结果表明, 聚乙二醇磷酸酯1000成功地修饰到碳酸钙的表面, 并得到平均直径为60 nm, 形貌为立方体的纳米碳酸钙晶体. 与碳酸钙(空白)样品相比, 表面处理碳酸钙的复合材料表现出更好的分散性和热稳定性. 采用Friedman方法计算了复合材料热分解的活化能. 聚对苯二甲酸乙二醇酯、 聚对苯二甲酸乙二醇酯/空白碳酸钙和聚对苯二甲酸乙二醇酯/表面处理碳酸钙的活化能分别为200.58, 214.86和219.50 kJ/mol, 进一步说明了表面处理碳酸钙更好地改善了聚对苯二甲酸乙二醇酯的热稳定性.     

Calibration of laser-ablation ICP-MS. Can we use synthetic standards with pneumatic nebulization?

An approach for the determination of trace element concentrations in high purity metals, using an inductively coupled plasma mass spectrometer (ICP-MS) with a laser-ablation system for direct solid sample introduction after calibration with nebulized liquid standards was made. Due to the inherent differences in the rate of sample introduction with laser-ablation and pneumatic nebulization, a matrix element must be used as an internal standard. This is problematical for elements that have no isotope with a relative abundance of less than 0.1 %, since the ion signals would be too high for direct measurement, and reduction of the ablation rate would compromise the sensitivity for trace elements. Due to the high stability of ICP-unit and mass filter of the instrument used, it was found that the tail of a mass-peak of the matrix element could be used as an internal standard. Therefore, a position at –0.5 amu from the matrix-isotope (e.g. ^62.5Cu in copper samples) was used for internal standardization. The standard deviation of this signal in a period of 2.5 h was 3.6% RSD with no notable drift when the laser ablation was used for sample introduction. The calibration of the matrix-element by nebulizing liquid standards showed that the ion signal measured on the peak-tail is directly proportional to the element concentration in the ICP. This indicates that the peak shape is not only stable, but also independent of the peak height. The advantages of this method lie in the easy preparation of calibration standards for quantitative measurements with a laser-ablation system and access to homogeneous standards for materials, that are difficult to homogenize in the solid state. The calibration of the traces is performed relatively to a fixed concentration of the matrix element. Calibrations were carried out for trace concentrations in high purity copper and good recoveries were obtained for high-purity reference standards. Received: 23 February 1998 / Revised: 20 July 1998 / Accepted: 25 July 1998     

Calibration of laser-ablation ICP-MS. Can we use synthetic standards with pneumatic nebulization?

An approach for the determination of trace element concentrations in high purity metals, using an inductively coupled plasma mass spectrometer (ICP-MS) with a laser-ablation system for direct solid sample introduction after calibration with nebulized liquid standards was made. Due to the inherent differences in the rate of sample introduction with laser-ablation and pneumatic nebulization, a matrix element must be used as an internal standard. This is problematical for elements that have no isotope with a relative abundance of less than 0.1 %, since the ion signals would be too high for direct measurement, and reduction of the ablation rate would compromise the sensitivity for trace elements. Due to the high stability of ICP-unit and mass filter of the instrument used, it was found that the tail of a mass-peak of the matrix element could be used as an internal standard. Therefore, a position at –0.5 amu from the matrix-isotope (e.g. ^62.5Cu in copper samples) was used for internal standardization. The standard deviation of this signal in a period of 2.5 h was 3.6% RSD with no notable drift when the laser ablation was used for sample introduction. The calibration of the matrix-element by nebulizing liquid standards showed that the ion signal measured on the peak-tail is directly proportional to the element concentration in the ICP. This indicates that the peak shape is not only stable, but also independent of the peak height. The advantages of this method lie in the easy preparation of calibration standards for quantitative measurements with a laser-ablation system and access to homogeneous standards for materials, that are difficult to homogenize in the solid state. The calibration of the traces is performed relatively to a fixed concentration of the matrix element. Calibrations were carried out for trace concentrations in high purity copper and good recoveries were obtained for high-purity reference standards. Received: 23 February 1998 / Revised: 20 July 1998 / Accepted: 25 July 1998     

A dedicated NAA method to determine the neutron spectrum monitor elements Co,Au and Lu with high accuracy in alloyed wires and foils

A dedicated NAA calibration method was developed for the determination of the neutron spectrum monitor elements Co, Au and Lu in alloyed wires and foils, with an accuracy of better than 1%. The method does not require quantitative micropipetting for preparing the standards, and leads to vanishing errors caused by flux inhomogeneities and by differences in counting geometry and gamma attenuation. Its performance was tested by analysing various NIST, IRMM and RX aluminium-based materials with certified or specified Co, Au or Lu content.     

Applications of inductively coupled plasma mass spectrometry and laser ablation inductively coupled plasma mass spectrometry in materials science

Inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS (LA-ICP-MS) have been applied as the most important inorganic mass spectrometric techniques having multielemental capability for the characterization of solid samples in materials science. ICP-MS is used for the sensitive determination of trace and ultratrace elements in digested solutions of solid samples or of process chemicals (ultrapure water, acids and organic solutions) for the semiconductor industry with detection limits down to sub-picogram per liter levels. Whereas ICP-MS on solid samples (e.g. high-purity ceramics) sometimes requires time-consuming sample preparation for its application in materials science, and the risk of contamination is a serious drawback, a fast, direct determination of trace elements in solid materials without any sample preparation by LA-ICP-MS is possible. The detection limits for the direct analysis of solid samples by LA-ICP-MS have been determined for many elements down to the nanogram per gram range. A deterioration of detection limits was observed for elements where interferences with polyatomic ions occur. The inherent interference problem can often be solved by applying a double-focusing sector field mass spectrometer at higher mass resolution or by collision-induced reactions of polyatomic ions with a collision gas using an ICP-MS fitted with collision cell. The main problem of LA-ICP-MS is quantification if no suitable standard reference materials with a similar matrix composition are available. The calibration problem in LA-ICP-MS can be solved using on-line solution-based calibration, and different procedures, such as external calibration and standard addition, have been discussed with respect to their application in materials science. The application of isotope dilution in solution-based calibration for trace metal determination in small amounts of noble metals has been developed as a new calibration strategy. This review discusses new analytical developments and possible applications of ICP-MS and LA-ICP-MS for the quantitative determination of trace elements and in surface analysis for materials science.     

ICP-MS测量环境样品中铀的非质谱干扰内标校正研究

内标的合理应用直接关系到测量结果的可靠性,通过外标与内标校正相结合的方法,实验研究了Y,Rh,In,Tb,Yb,Tl,Bi,Re作为内标对ICP-MS测量铀的非质谱干扰的校正效果。对于非抑制/增强基体效应,各内标元素校正结果明显优于无内标校正结果,高质量数内标元素Tb,Yb,Re,Tl,Bi可获得较好的校正效果,校正偏差优于5%,其中以Tl为最佳;对于盐度较高的样品溶液,由于基体对待测元素和内标元素产生了明显不同的抑制/增强效应,因此各内标校正结果均不理想,这表明内标对可溶性固体引起的抑制/增强效应的校正能力有限。在铀的测量中,对于含盐度在300～500μg/mL的样品,内标校正造成的偏差可达到5%～10%;对于盐度在500μg/mL以上的样品,内标校正造成的偏差很可能超过10%或者更高。     

Reduction of interferences in graphite furnace atomic absorption spectrometry by multiple linear regression modelling

The multivariate effects of Na, K, Mg and Ca as nitrates on the electrothermal atomisation of manganese, cadmium and iron were studied by multiple linear regression modelling. Since the models proved to efficiently predict the effects of the considered matrix elements in a wide range of concentrations, they were applied to correct the interferences occurring in the determination of trace elements in seawater after pre-concentration of the analytes. In order to obtain a statistically significant number of samples, a large volume of the certified seawater reference materials CASS-3 and NASS-3 was treated with Chelex-100 resin; then, the chelating resin was separated from the solution, divided into several sub-samples, each of them was eluted with nitric acid and analysed by electrothermal atomic absorption spectrometry (for trace element determinations) and inductively coupled plasma optical emission spectrometry (for matrix element determinations). To minimise any other systematic error besides that due to matrix effects, accuracy of the pre-concentration step and contamination levels of the procedure were checked by inductively coupled plasma mass spectrometric measurements. Analytical results obtained by applying the multiple linear regression models were compared with those obtained with other calibration methods, such as external calibration using acid-based standards, external calibration using matrix-matched standards and the analyte addition technique. Empirical models proved to efficiently reduce interferences occurring in the analysis of real samples, allowing an improvement of accuracy better than for other calibration methods.     

Determination of trace and ultra-trace amounts of noble metals in geological and related materials by graphite-furnace atomic-absorption spectrometry after separation by ion-exchange or co-precipitation with tellurium

Two methods for determining mug/g and ng/g levels of the noble metals, except for osmium, in ores, concentrates, mattes, and silicate and iron-formation rocks are described. After sample decomposition with hydrofluoric acid and aqua regia, followed by fusion of any insoluble residue with sodium peroxide, the noble metals are separated from the matrix elements by either cation-exchange or co-precipitation with tellurium. The resulting eluate, or the solution obtained after dissolution of the tellurium precipitate, is evaporated to dryness and the noble metals are ultimately determined in a 1M hydrochloric acid medium by graphite-furnace atomic-absorption spectrometry. The ion-exchange method is recommended for the determination of mug/g levels of gold, silver and platinum-group elements, whilst the tellurium co-precipitation method is recommended for ng/g levels of platinum-group elements. The latter method is not recommended for the determination of ng/g levels of silver and gold in rocks, because of interference from tellurium during atomization in the furnace. Results obtained by these methods for 15 international reference samples, including four Canadian iron-formation rocks, are compared with other published data.     

Introducing Doolittle multivariate calibration algorithm for infrared spectrometric determination of STTP,SS, and SC in Iranian washing powder

The basic principle of Doolittle multivariate calibration algorithm (DMCA) was investigated and used for simultaneous quantitative determination of sodium tripolyphosphate (STPP), sodium sulfate (SS), and sodium carbonate (SC) in commercial washing powders with serious overlapping. The process of the Doolittle decomposition algorithm (DDA) is implemented by lower and upper (LU) triangular matrix decomposition which is robust and convenient. Then it was applied to overcome the problem of overlapping spectra of different components in the detergent washing powder. The root mean square error of prediction (RMSEP) for DMCA is 0.084 which confirms the improvement in accuracy, in comparison with K-Matrix (KM) (RMSEP=0.118). It was demonstrated that DDA can avoid matrix inverting, reduce the orders of matrices, and needs a little time for analysis. Therefore, it has bright prospects in chemometrics and it is feasible that the Doolittle algorithm could be applied to the practical determinations in real samples with spectral overlapping.     

Determination of major, minor and trace elements in rock samples by laser ablation inductively coupled plasma mass spectrometry: Progress in the utilization of borate glasses as targets

The present work is a continuation of a research study performed at our laboratory aiming at the multielement analysis of rock samples (basalts and shale) by inductively coupled plasma mass spectrometry in combination with laser ablation using borate glasses as analytical targets. Argon, nitrogen-argon mixtures and helium were evaluated as cell gases, the latter confirming its better performance. Different operational parameters of the laser, such as gas flow, energy, focus, scanning speed and sampling frequency were optimized. External calibration was made with standards prepared by fusion of geological reference materials (basalts 688 and BCR-2, obsidian SRM 278, and shale SGR-1) of different mass fractions in the meta-tetra borate matrix. Coefficients of determination (R²) were > 0.99 for 30 elements from o total of 40 determined. Method validation was then performed using additional certified reference materials (BHVO-2, BIR-1, SCo-1) produced as borate targets in a similar way. Accuracies were better than 10% for most of the elements studied and analytical precisions, calculated from the residual standard deviations of calibration curves were, typically, between 6% and 10%. Additionally, the semiquantitative TotalQuant® technique was applied, which gave, within the expected uncertainty for this calibration technique, concordant results when compared to the quantitative external calibration procedure. Both methods were then used for the analysis of marine shale samples, which are of great geological interest in petroleum prospecting.     

Rapid Determination of Methylcyclopentadienyl Manganese Tricarbonyl in Gasoline by FAAS

ABSTRACT

A new method using microemulsified samples is presented. The method is suitable for the determination of manganese, present as methylcyclopentadienyl manganese tricarbonyl, in gasoline in the range 0～75μg ml^?1. The method has the advantage of simplicity, speed and the use of aqeous standards for calibration instead of organic standards. Coexistent elements do not disturb the determination. Results obtained by this method were better than those obtained by other methods for the same samples.