MIC-SSMS analyses of eight new geological standard glasses

To obtain suitable geological reference materials for microanalytical purposes, a set of eight natural glasses was prepared by direct fusion of rock chips. Multi-ion counting spark source mass spectrometry (MIC-SSMS) has been applied for trace element analysis of these reference materials. The overall analytical uncertainty of the MIC-SSMS results was determined by considering 14 possible sources of errors. It generally ranges between < 2–7% depending on the element and its concentration. Nearly all MIC-SSMS data agree with the reference values within 0–10%, indicating that the estimate of the overall analytical uncertainty is reasonable. Received: 21 December 1998 / Revised: 2 March 1999 / Accepted: 3 March 1999     

MIC-SSMS analyses of eight new geological standard glasses

To obtain suitable geological reference materials for microanalytical purposes, a set of eight natural glasses was prepared by direct fusion of rock chips. Multi-ion counting spark source mass spectrometry (MIC-SSMS) has been applied for trace element analysis of these reference materials. The overall analytical uncertainty of the MIC-SSMS results was determined by considering 14 possible sources of errors. It generally ranges between < 2–7% depending on the element and its concentration. Nearly all MIC-SSMS data agree with the reference values within 0–10%, indicating that the estimate of the overall analytical uncertainty is reasonable. Received: 21 December 1998 / Revised: 2 March 1999 / Accepted: 3 March 1999     

Assessment of the ICP-MS method using the interlaboratory QA study of two Polish soil RMs

 Under an international collaborative certification programme, two new Polish soil reference materials, PL-1 (loess) and BPGM-1 (sandy loam soil), were analysed for 34 trace elements including all the rare earth elements using the acid decomposition method and inductively coupled plasma - mass spectrometry (ICP-MS). After the certification by the organisers, the analytical data obtained at our institute were compared with the certified data. 'Z-score' values calculated for individual trace elements helped in the assessment of the quality of the data. While the majority of the data obtained on ICP-MS was very precise and accurate, some of the data especially for elements such as Zr, Hf and Nb suffered from incomplete dissolution of the sample and spectroscopic interferences. For some trace elements, certified data are not available for comparison. These features together with the usefulness of interlaboratory collaborative programmes and ICP-MS for the certification of soil reference materials are discussed. Received: 6 August 1999 / Accepted: 28 February 2000     

Reference materials in the Russian system of accreditation of analytical laboratories

 This article is devoted to the role of reference materials (RMs) in chemical analysis and their main applications in analytical laboratories. The principal requirements of the RMs used in accredited laboratories in the Russian Analytical Laboratories Accreditation System (SAAL) are presented. These include the basic regulatory and metrological requirements of RMs. Finally, a review of the provision of RMs used for the analytical control of various test objects is presented. Received: 9 August 1998 / Accepted: 9 November 1998     

Investigation of the analytical performance of gliding spark source mass spectrometry (GSSMS) for the trace analysis of nonconducting materials

A radiofrequency (rf) spark discharge in vacuum developing across the surface of dielectrics – a so-called gliding spark – has been applied to the direct mass spectrometric trace analysis of nonconducting materials. The special configuration of the electrodes strengthened the electric field over the surface of a nonconducting sample and created optimum conditions for the sputtering and ionization of the sample material. Mass spectrometric investigations of the charge composition of atomic ion and molecular ion formation in radiofrequency gliding spark plasma showed a significant difference to that of the original rf spark discharge between two conducting electrodes. The analytical figures of merit (reproducibility, relative sensitivity factors and detection limits of chemical elements) of gliding spark source mass spectrometry have been studied by using the glass standard reference materials NIST SRM 610 and 611 for the determination of trace elements in glass matrix. Received: 31 March 1999 / Revised: 10 May 1999 / Accepted: 13 May 1999     

Identification of chemical substances in analytical measurements

 Characteristic features of identification procedures of chemical substances are described and the metrological requirements for identification are discussed. The procedures are considered to be rigorous enough, if quantitative criteria such as the measure of similarity between physicochemical properties or spectra of the unknown substance and reference materials are used. Identification involves expert opinion which is of prime importance in the analysis of samples of unknown composition. The reliability of substance recognition can be increased by selecting highly qualified personnel, establishing a good information supply, using an on-line combination of separation and detection instruments such as chromatography-spectrometry and estimating the probability of identification. Standard conditions for reliable identification including quantitative criteria are examined using gas chromatography-mass spectrometry as an example. Received: 19 August 1998 / Accepted: 12 September 1998     

Confocal fluorescence and Raman microscopy in industrial research

 Modern chemical and pharmaceutical industrial research benefits from improved spectroscopic tools. New developments in confocal fluorescence and Raman microscopy lead to an increase in sensitivity, selectivity and speed of microscopic imaging and fluctuation analysis resulting in a better understanding of structure–property relationships essential for targeted development. In this paper we report on the application of fluorescence and Raman microscopy for characterizing the morphology of polymeric multiphase solid-state samples and on new developments in the corresponding correlation spectroscopies for the characterization of the dynamics of complex colloidal systems in the liquid state. In the case of fluorescence new technological opportunities are gained by two-photon excitation. Received: 5 February 1998 Accepted: 16 February 1998     

Geostandards and geochemical analysis

Progress in geochemical analysis depends on progress in geostandards. The present state of the availability and quality of the geostandards is reviewed for major and trace elements. The several geochemical methods employed are evaluated by their performances in the characterization of geostandards. Signs of progress are visible in the quality of geostandards for major and “common” trace elements. There are also new developments in geoanalytical methods. It is hoped that optical emission inductively coupled plasma spectrometry will play an increasing role in the characterization of trace elements which are normally present in less than 10 ppm concentration levels.Like it or not, progress in geochemical analysis is intimately tied up with the quality of geochemical reference samples (GRS). The converse is true as well; therefore, how well and to what extent international geochemical reference samples are characterized for their chemical composition reflect in a way the current status of geoanalytical methods employed the world over.     

Accreditation system for reference material producers and certified reference materials for iron and steel in Japan

  ISO 9000 series strictly requires traceability to national or international measurement standards. It is becoming more necessary to make clear the concept of traceability of measurement standards with respect to chemical composition and to accredit the reference material producers. In Japan, the accreditation system for reference material producers is considered to satisfy the requirement of ISO Guide 34, ISO 9000 series and ISO/IEC Guide 25, while the producer fulfills the concept of traceability of measurement standards. This paper describes the production of iron and steel reference materials in Japan relating to the international standardization of methods (written standards) and accreditation of reference material producers. Received: 11 October 1996 Accepted: 5 December 1996     

The non-destructive determination of REE in fossilized bone using synchrotron radiation induced K-line X-ray microfluorescence analysis

The sensitivity and applicability of the synchrotron radiation induced X-ray microfluorescence (μ-SRXRF) spectrometer at the Hamburg synchrotron laboratory Hasylab for the determination of the distribution of trace concentrations of rare-earth elements (REE) in fossilized bone are discussed and critically compared to those of other trace analytical methods such as instrumental neutron activation analysis (INAA) and LAMP-ICPMS (laser ablation microprobe inductively-coupled plasma mass spectrometry). Measurements were carried out on two bone samples from contrasting terrestrial depositional environments at Olduvai Gorge (Tanzania). Results indicate that the microdistribution of the REE in these biological materials is not homogeneous and that the relative abundance of these elements can provide information on the palaeoenvironment during the fossilization process. The heterogeneous distribution of the REE can be determined in a quantitative and completely non-destructive manner provided the concentrations of individual REE are above 10 μg/g. Received: 18 January 1998 / Revised: 6 October 1998 / Accepted: 10 October 1998     

Certified reference materials for the quality control of EDTA- and acetic acid-extractable contents of trace elements in sewage sludge amended soils (CRMs 483 and 484)

 The ecotoxicity and mobility of trace elements in soils are often evaluated through analytical results resulting from operationally-defined determinations (single and sequential extractions), e.g. based on EDTA, acetic acid etc. extractions. The significance and comparability of these results is highly dependent on the procedures used (standardized protocols or standards adopted by international bodies) and their quality control relies on the availability of reference materials certified following these strictly applied procedures. Recognizing the need to harmonize some of the extraction schemes currently used for soil analysis, the Measurements and Testing Programme (formerly BCR) has organized a series of interlaboratory studies, the first aim of which was to evaluate EDTA- and acetic acid-extraction procedures and the second objective was to certify reference materials for their extractable trace element contents. Two sewage amended soils have been prepared for this purpose, originating respectively from Scotland and Catalonia. This paper describes the preparation, homogeneity and stability studies, and gives an overview of the certification campaign. Received: 6 May 1996/Revised: 14 June 1996/Accepted: 27 June 1996     

Matrix reference materials – provision in Australia

 Until quite recently, Australia has not been much involved in the preparation and certification of matrix reference materials for chemical testing. Even today, the vast bulk of chemical reference materials used in Australia are imported from other world producers. Increased international focus on the accuracy, traceability and comparability of chemical measurements has led to the establishment of the National Analytical Reference Laboratory (NARL) within the Australian Government Analytical Laboratories. Part of the work of NARL will be to supply matrix reference materials, not available from existing sources, to meet specific Australian requirements. This need has been addressed in the past by a combination of industry and government initiatives. Examples include a series of certified matrix reference materials for chemical testing of iron ore, coal and mineral sands produced by Standards Australia and a series of three animal fat matrix reference materials certified for a range of pesticide residues produced by the Australian Chemical Standards Laboratory (now part of NARL). To make effective use of limited resources, it will be important for NARL to focus on identified priorities and to maximise the use of available Australian resources and expertise through technical collaboration for reference material production. An important part of this process should be input on needs and priorities from reference material "users" such as government legislators, regulatory authorities, standards setting bodies, industry and the analytical community. The aim will be to produce matrix certified reference materials that are traceable to SI or other international standards at a stated level of measurement uncertainty.     

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     

Evaluation of laboratory performance in IMEP water interlaboratory comparisons

The aim of International Evaluation Programme (IMEP) is to present objectively the quality of chemical measurements. Participants in IMEP compare their reported measurement results with independent external certified reference values with demonstrated traceability and uncertainty, as evaluated according to international guidelines. Three major interlaboratory comparisons (ILCs), IMEP-6, IMEP-9 and IMEP-12, on trace elements in water were carried out from 1994 to 2000. Participants' results for Cd, Fe and Pb concentrations from these three different IMEP water ILCs were compared by means of suitable performance indicators. The performance evaluation criteria were set according to the requirements stated in the Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. Two different performance indicators were selected for evaluation of the individual participants' results: the commonly used z-score and the not so well-known E _n number. The group performance indicator is based on the variation of z-scores. To assess the individual measurement performance, not only the deviation of the reported measurement values from the certified reference value, but also criteria for maximum and minimum acceptable uncertainties were taken into account. The participants' performance is also reviewed by means of using a simple graphical tool, called “Naji-plots”.     

Application of a double-focusing magnetic sector inductively coupled plasma mass spectrometer with laser ablation for the bulk analysis of rare earth elements in rocks fused with Li2B4O7

Results of the use of a double-focusing, magnetic sector inductively coupled plasma mass spectrometer (ICP-MS) with ultraviolet (UV) laser ablation (LA) are presented for the bulk analysis of rare earth elements (REEs) in rocks fused with Li₂B₄O₇. The sample preparation procedure used a sample to flux weight ratio of 1 : 7, and was identical with a procedure routinely used for X-ray fluorescence (XRF) analyses of major and minor elements in geological materials. Calibration was based on a total of 18 international standard reference materials (SRMs), and Ba was used as an internal standard element for all REEs. The calibration curves were constructed using a weighted regression model. The use of internal standard, without exception, improved the correlation coefficients significantly. The 3σ detection limits were established by a blank sample of SiO₂ spiked with Ba, and were in the range from 0.003 μg g^–1 (¹⁵⁹Tb) to 0.051 μg g^–1 (¹⁴⁰Ce). The use of a large set of SRMs for calibration gave a good basis for the evaluation of analytical quality, and extensive data for calculated analytical uncertainty are presented. Instrumental precision and the repeatability of the method were studied separately, and no significant difference in these two sets of parameters were found, indicating that the spread of results predominantly was connected to the instrumental measurements. Repeated ablations on the surface of a disk did not influence subsequent measurements with XRF, showing that the fused disks can be stored for future use in XRF and/or LA-ICP-MS analysis. Received: 12 February 1998 / Revised: 6 April 1998 / Accepted: 17 April 1998     

Generalized extended empirical bond-order dependent force fields including nonbond interactions

We present a general approach for describing chemical processes (bond breaking and bond formation) in materials using force fields (FF) that properly describe multiple bonds at small distances while describing nonbond (Coulomb and van der Waals) interactions at long distances. This approach is referred to as the generalized extended empirical bond-order dependent FF. In this paper we use the Brenner empirical bond-order dependent FF for the short-range interactions and report applications on the energetics and structures of graphite crystal, dynamics of molecular crystals, and distortions of bucky tubes. Received: 7 August 1998 / Accepted: 26 October 1998 / Published online: 16 March 1999     

Trends in certified reference materials for the speciation of trace elements.

The measurement of the chemical species of elements (instead of the total element concentration) has become an irreversible trend in analytical chemistry. The motivation lies in the fact that the biochemical and geochemical behaviour of an element is governed by its species. Quality assurance of the analytical procedures used for speciation analysis requires the analysis of representative reference materials, certified for the relevant species. Up to now the number of existing certified reference materials for trace element species is very limited. The most important ones are environmental CRMs certified for trialkyltin compounds, methylmercury, Cr(III)/Cr(VI) and food CRMs certified for arsenic species and methylmercury. Major developments are to be expected in CRMs focussed on environmental problems, including waste treatment, on bioavailability of trace elements in food and on bio-monitoring in occupational health and hygiene. It is, however, unlikely that the producers of CRMs will ever be able to cover all needs. Add to this that many, very active species are notoriously unstable and/or short living and require in-situ analysis. This will lead to different analytical developments, such as analyses in-situ, where the classical concept of CRMs may not stand firm anymore.     

Quality control and reference materials in speciation analysis

This contribution describes the need and some strategies for a rigid quality control in speciation analysis. Firstly, the term “chemical speciation” is defined and differentiated from experimental concepts now called “operationally defined speciation” or “functionally defined speciation”. The need for quality control in speciation is given by the big number of sources of errors during sampling, sample preparation, separation and detection. Errors such as stability problems, contaminations or losses, spectral interferences etc. are discussed. On the other hand, several concepts for problem solutions are described. One of these solutions is the use of certified reference materials (CRM). Unfortunately, species-certified CRM are only available for few matrices and few elements, e.g. mercury in fish or sediments, lead in solutions and urban dust etc. Therefore special quality control strategies are necessary for each part of the analytical speciation procedure. Several examples of such procedures are given and discussed. Received: 25 July 1998 / Accepted: 8 August 1998     

Trends in certified reference materials for the speciation of trace elements

The measurement of the chemical species of elements (instead of the total element concentration) has become an irreversible trend in analytical chemistry. The motivation lies in the fact that the biochemical and geochemical behaviour of an element is governed by its species. Quality assurance of the analytical procedures used for speciation analysis requires the analysis of representative reference materials, certified for the relevant species. Up to now the number of existing certified reference materials for trace element species is very limited. The most important ones are environmental CRMs certified for trialkyltin compounds, methylmercury, Cr(III)/Cr(VI) and food CRMs certified for arsenic species and methylmercury. Major developments are to be expected in CRMs focussed on environmental problems, including waste treatment, on bioavailability of trace elements in food and on bio-monitoring in occupational health and hygiene. It is, however, unlikely that the producers of CRMs will ever be able to cover all needs. Add to this that many, very active species are notoriously unstable and/or short living and require in-situ analysis. This will lead to different analytical developments, such as analyses in-situ, where the classical concept of CRMs may not stand firm anymore.