Comparison of methods used for the preparation of biological CRM's

The starting material for two certified and one candidate reference material was obtained from dried grass specially cultivated on a selected and well prepared soil. The Community Bureau of Reference (BCR) of the Commission of the European Communities produced two certified reference materials (CRM's) from this dried grass: a rye grass material (CRM 281) certified in 1988 for the quality control of trace and toxic element analyses and a hay powder material (CRM 129) certified in 1989 for monitoring trace and minor elements. A fraction of the dried grass was used in 1993 for the preparation of a hay powder with a particle size of <63 m using newly developed grinding techniques.This paper compares the production methods of these three materials and the obtained particle size distribution of the powders. The analytical evaluation of these production methods was carried out by solid sampling Zeeman atomic absorption spectrometry for the determination of Cd, Pb and Zn.     

New marine biological reference materials for trace metals

Summary A list of reference materials and certified reference materials (CRM's) useful to the marine analytical chemist for validation of trace element determinations is given. The preparation and certification for the trace element content of two new marine biological reference materials, dogfish flesh (DORM-1) and dogfish liver (DOLT-1), is described.     

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.     

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.     

Statistical estimation of the influence of mineralization methods on the results of heavy metals determination in cereals by the DPASV method

Summary The Community Bureau of Reference (BCR) has undertaken the development of a range of reference materials designed to meet the principal needs for food analysis and measurement. This work falls within the scope of a general collaborative programme designed to improve measurement accuracy and comparability within Europe.The development of well characterised food reference materials frequently poses serious difficulties, not only with respect to stability and homogeneity, but also for accurate certification. A pre-requisite for accurate certification is a high level of agreement between the collaborating laboratories, preferably when employing methods based on different principles.Especially for trace organic analysis, it is necessary to carry-out preliminary intercomparisons of candidate certification methods in order to identify and eliminate the major sources of error. This process is greatly facilitated if the critical steps such as recovery, clean-up and final determination can be studied separately. The paper describes this approach by reference to three milk-powders which were recently certified for their aflatoxin M₁ content and presents results for bovine muscle, bovine liver and pig kidney CRMs recently certified for toxic and nutritional element.     

Sample pre-treatment methods for the trace elements determination in seafood products by atomic absorption spectrometry

Different sample pre-treatments for seafood products have been compared with determine trace elements (As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se and Zn) by flame atomic absorption spectrometry (FAAS) and electrothermal atomic absorption spectrometry (ETAAS). Classic pre-treatments as microwave assisted-acid digestion and the slurry sampling technique were compared with new procedures such as microwave energy or ultrasound energy assisted-acid leaching process and enzymatic hydrolysis methodologies based on the use of pronase E. The methods were applied to DORM-1 and DOLT-1 reference materials with certified contents for the studied elements. The Student-Newman-Keuls (SNK) method was used to compare with element concentration means obtained with each sample pre-treatment and also the certified concentration means in both reference materials. Multivariate techniques such as principal components analysis (PCA) was also applied to comparative purposes.     

Primary standards in activation analysis

The availability of natural matrix reference materials evaluated for trace element content has resulted in their widespread use as standards (i.e., calibration materials; comparators) for instrumental neutron activation analysis (INAA). Due to the uncertainties associated with their certified values, the limited number available, and the relative matrix independence of INAA, these reference materials are more properly utilized as quality assessment materials, after calibration of the INAA analytical system with true primary standards. Terminology is defined, the use of matrix reference materials to evaluate the analytical system is discussed, techniques for the accurate preparation of primary standards for trace element analyses are reviewed, and necessary precautions in the accurate comparison of samples to standards are presented.     

The use of reference materials in the fossil fuels quality control

The determination of trace elements in fossil fuels is of primary importance to achieve correct evaluation of environmental impact of power plants. The characterization of coals and fuel oils can be carried out by several analytical techniques such as ICP-MS, FI-HG-AAS, ETA-AAS, ICP-AES and XRF. The accuracy of the analysis, done to routine basis, can be systematically checked by means of the reference materials available or comparing the results obtained by different techniques. Quality control activities in the field of trace element determination in fossil fuels (coal and fuel oil) are described. The determination of As, Hg and Se in coals was carried out by different techniques (NAA, FI-HG-AAS and FI-ICP-MS) together with the determination of several trace metals in residual fuel oils by NAA, ETA-AAS and ICP-MS. The use of certified reference materials in order to check the accuracy of procedures is discussed and the results obtained for NIST 1632a and NIST 1632b (coal samples) and NIST 1634b and NIST 1619 (fuel oil samples) are reported.     

Topical Problems in Elemental Analysis of Advanced Ceramic Materials

Selected prominent problems in the analysis of advanced ceramic materials are surveyed. The importance of reliability of results is discussed in the field of elemental trace- and microanalysis in view of its interaction with economy, power of detection, local resolution and speciation selectivity. Particular problems in the analysis of major constituents, trace components and microlocal distributions are based on the striking propertics of ceramics; they are exemplified. Analytical assistance must start from the beginning of the production processing, in the preparation of the powdered base materials. Determination of the stoichiometry requires high accuracy and differentiation of chemical species in bulk and surface analysis of ceramic base powders. Element trace determination by direct instrumental methods requires standard reference materials for calibration; these are currently inavailable in a sufficient variety. For optimum reliability and power of detection, element traces must be prepared in isolated form in a small excitation volume for analysis. A review on the state-of-the-art of wet-chemical combined procedures is presented. Decomposition position procedures are emphasized, due to their risk of contributing severe systematic error. Combustion in elementary fluorine is presented for decomposition of refractory materials. The performance of some direct procedures is discussed. Very efficient methods are available for element trace determinations in ceramic materials, offering high detection power. Several approaches for high-resolution local microanalysis in non-conductive ceramic materials are identified as the most promising development in the analysis of sintered compact ceramic products and devices.     

Evaluation of the use of microwave oven systems for the digestion of environmental samples

In most chemical analyses for inorganic determinations in environmental matrices the sample is physically destroyed by dissolution, calcination etc. These digestion procedures have to be validated in order to ensure that no contamination and/or losses have occurred which could affect the accuracy of the final results obtained; this validation can be made by using certified reference materials (CRMs).In the recent past, microwave digestion procedures have been developed and have been shown to offer the benefits of rapid sample preparation and reduced contamination risks; however, an incomplete dissolution was suspected in some cases, e.g. in interlaboratory exercises, for the analysis of organic matrices.The aim of this study was to test microwave digestion procedures for different environmental CRMs and to evaluate the suitability of these methods for the determination of some trace elements. The effects of chemical species (As, Hg and Se-species) on the total element recovery after digestion are discussed.     

Collaborative study to improve the quality control of trace element determinations in polymers. Part 1. Interlaboratory study

In order to control the quality of trace element determinations in polymer, the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a project of which the final aim is to certify polymer reference materials for their contents of a range of trace elements. The first part of this project consisted in an interlaboratory study which aimed at testing the feasibility of preparation of candidate polymer reference materials and to detect and remove most of the pitfalls observed in trace element determinations. This paper presents the results of this interlaboratory study carried out prior to the certification campaign. Received: 22 April 1999 / Revised: 21 June 1999 / Accepted: 21 June 1999     

Collaborative study to improve the quality control of trace element determinations in polymers. Part 1. Interlaboratory study

In order to control the quality of trace element determinations in polymer, the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a project of which the final aim is to certify polymer reference materials for their contents of a range of trace elements. The first part of this project consisted in an interlaboratory study which aimed at testing the feasibility of preparation of candidate polymer reference materials and to detect and remove most of the pitfalls observed in trace element determinations. This paper presents the results of this interlaboratory study carried out prior to the certification campaign. Received: 22 April 1999 / Revised: 21 June 1999 / Accepted: 21 June 1999     

The use of multi-element concentration datasets obtained by INAA in the identification of sources of environmental pollutants

Trace element concentration patterns can be used for the identification of objects or materials. Early applications were related to the elucidation of identity or origin of objects. Recently, a number of applications have been reported of the use of trace element concentration patterns to recognize and identify components of mixtures of materials, mainly of environmental interest. In the present paper two examples are discussed of application of Target Transformation Factor Analysis to trace element concentration patterns, to identify sources of heavy metal air pollution. The materials studied are air particulate matter and epiphytic lichens used as biological accumulator.     

Analytical Standards and Methods for the Determination of Polynuclear Aromatic Hydrocarbons in Environmental Samplest

Abstract

Standard reference materials (SRM's) have been produced, certified, and issued by the United States National Bureau of Standards (NBS) since 1905. NBS currently issues more than 1000 SRM's of various types, including nuclear materials, rubber, clinical and environmental trace metal standards. The most recent addition to this group is a series of environmental trace organic materials with certified concentrations of selected polynuclear aromatic hydrocarbons (PAH), phenols, and N-heterocyclic compounds. Until recently, trace organic SRM's were non-existent due to the lack of analytical methodology necessary for certification. Details concerning the analytical methods developed and used for certification of the concentrations of several PAH in SRM's 1580 (Organics in Shale Oil), 1644 (Generator Columns for PAH in water), 1647 (PAH in Acetonitrile), and 1649 (Urban Particulate Matter) are given along with some suggested uses for these SRM's.     

Laser Ablation Inductively Coupled Plasma Mass Spectrometry for Determination of Trace Elements in Geological Glasses

 Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used as a powerful multielement analytical method for trace analysis of geological glasses which are useful as reference materials for geochemical in-situ microanalytical work. The quantification of the analytical results was carried out using the BCR-2G and NIST 612 glass standard reference material (SRM). The experimentally determined relative sensitivity coefficients (RSC) for both SRMs vary between 0.2 and 3 for most of the elements, with increasing mass an increasing of relative sensitivity coefficients was observed. The relative standard deviation (RSD) for determination of trace element concentration of most elements (N=3) are between 2 and 10%. The determination of trace elements in various geological glasses by LA-ICP-MS yielded a good agreement with the reference values and those results of other trace analytical methods. Received October 15, 1999. Revision April 14, 2000.     

Matrix certified reference materials for environmental monitoring from the National Metrology Institute of Japan (NMIJ)

Matrix certified reference materials (CRMs) are playing an increasingly important role in environmental monitoring in Japan. The National Metrology Institute of Japan (NMIJ)/National Institute of Advanced Industrial Science and Technology (AIST) has been developing matrix CRMs for environmental monitoring since 2001, and has issued nine kinds of CRMs as NMIJ CRMs. The development of the CRMs was conducted in NMIJ in cooperation with candidate material producers. The isotope dilution mass spectrometry (IDMS) was principally adopted to give reliable certified values. Meanwhile, two or more analytical methods, whose levels of accuracy were well evaluated, were applied to avoid any possible analytical bias. Two typical certification processes, the certification of river water CRMs for trace element analysis and that of marine sediment CRMs for PCB and organochlorine pesticide analysis, are outlined as examples. Presented at -- “BERM-10” -- April 2006, Charleston, SC, USA.     

An investigation of methods for the analysis of zinc concentrates for their total fluoride contents

Accurate determination of trace fluoride down to 6.6 mug/g in zinc concentrate samples is found to be most expediently performed potentiometrically with a fluoride ion-selective electrode and a single-point standard addition after decomposition of the sample by potassium hydroxide fusion. The lower limit of measurement may be reduced to 1.8 mug/g if distillation from tungsten oxide flux is used in place of the fusion, but the analysis takes longer. The need for reliable fluoride data for zinc concentrate standard reference materials is exemplified and results for CANMET zinc concentrate MP-1 are given. The failure of some of the methods used to analyse standard siliceous materials is discussed.     

Certification of a second-generation biological reference material (freeze-dried human serum) for trace element determinations

The certification of a second-generation biological reference material (freeze-dried human serum) for trace element determinations is described. The material was prepared under rigorously controlled conditions to avoid extraneous additions. Analytical data were obtained by the authors as well as by numerous other intra- and extra-mural investigators, solicited on the basis of established experience in determining selected elements. For 14 trace elements (aluminium, chromium, manganese, iron, cobalt, copper, zinc, arsenic, selenium, bromine, rubidium, molybdenum, cadmium and caesium) certified values (in ng g^?1 or μg g^?1 dry weight) are listed; for an additional element (nickel) a best estimate (in ng g^? dry weight) is added. Trace element concentrations in the material, which is available to the scientific community, closely approximate those in normal, lyophilized blood plasma or serum samples. The material thus provides the means to check the accuracy and precision of analytical procedures for quantifying low-level trace elements in the best possible conditions and to detect errors that can easily be overlooked when reference materials with higher levels of trace elements are used. In addition, and in contrast to already existing biological reference materials with high levels of trace elements, it offers the possibility of identifying unsuspected errors at the sample preparation stage.     

Preparation of biological and environmental reference materials at CBNM

Summary Since 1984, CBNM has been officially responsible for supporting the BCR programme for CRM storage, distribution and sale activities for the development of methods for preparation, conditioning and packing for reference materials, as well as actually preparing candidate CRMs. This has allowed CBNM to set up a new laboratory with unique facilities for the preparation of biological and environmental reference materials, in particular for organic and inorganic trace analysis. The main technical facilities developed at CBNM and additional equipment built to CBNM specifications by external companies are described. They have been used for the preparation of a variety of reference materials including cod fish, pig liver, offal, spiked milk, curd, orange juice, clover, lettuce, paprika, tomato, fly ash, soils and sediments.     

Optode for uranium(VI) determination in aqueous medium

A quantification procedure of trace elements during colloid size fractionation was developed and validated. This procedure is based on the hyphenation between Asymmetrical Flow Field-Flow Fractionation (As-Fl-FFF) and Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The optimisation of the procedure was performed on a soil leachate spiked with six trace elements selected for their environmental and health impact (As, Cd, Sb, Se, Sn and Pb). The elements in the spiked sample were on-line monitored during the fractionation. The validation was carried out by comparison with a second off-line quantification procedure based on fraction collection and total element analysis by ICP-MS. This off-line one was previously validated using reference materials. Finally, the analytical performances of the two procedures were compared.