SI-traceable certification of the IMEP-12 water sample combining contributions from different reference laboratories

In the International Measurement Evaluation Programme (IMEP-12) comparison, a synthetically prepared water sample was offered to the analytical laboratories to perform measurements of As, B, Cd, Cr, Cu, Fe, Mg, Mn, Ni and Pb. The choice of elements to be measured was based on EU legislation, which the comparison was aiming to support. As to the IMEP policy, the laboratories’ results were presented according to the certified/assigned reference values established by several reference laboratories all around the world. The performed certification campaign is described in detail in this paper. Isotope dilution mass spectrometry (IDMS) was applied as a primary method of measurement (PMM), whenever possible, to achieve SI-traceable results. Apart from IDMS for reference measurements of some elements, k _o-neutron activation analysis (k _o-NAA) and external calibration (Ext-Calib) using inductively coupled plasma-mass spectrometry (ICP-MS) were applied. The reference values were characterised as “certified” (for B, Cd, Cr, Cu, Fe, Mg, Ni and Pb) or “assigned” (for As and Mn) according to the IMEP policy. Measurement uncertainty of the certified/assigned reference values was calculated according to the ISO/BIPM guide using the specialised software GUM Workbench.

     

Establishment of SI-traceable reference values for the content of various elements in the IMEP-14 sediment sample

For the first time in the International Measurement Evaluation Programme (IMEP)-14, a sediment sample was offered to analytical laboratories to perform measurements of As, Cd, Cr, Cu, Fe, Pb, Hg, Ni, U and Zn. In line with IMEP policy, the results were presented according to the certified / assigned reference values established by several reference laboratories around the world. The certification campaign is described in detail. Isotope dilution mass spectrometry was applied as a primary method of measurement, whenever possible, to achieve SI-traceable results. For reference measurements of As, Fe, Hg and Zn, k₀-neutron activation analysis and Zeeman atomic absorption spectrometry were applied. The reference values (ranges) were characterised as ”certified” (for Cd, Cr, Pb, Ni and U) or ”assigned” (for As, Cu, Fe, Hg and Zn) according to IMEP policy. The measurement uncertainty of the certified / assured reference values was calculated according to the ISO/BIPM Guide. Received: 7 June 2001-10-27 Accepted: 19 August 2001     

International Measurement Evaluation Programme: IMEP-9, trace elements in water

The International Measurement Evaluation Programme (IMEP) is an interlaboratory comparison scheme, founded, owned and coordinated by the Institute for Reference Materials and Measurements (IRMM) since 1988. IMEP-9 is the third round of trace elements in water evaluation following IMEP-3 and IMEP-6. Reference values for 15 elements stating total concentrations and combined uncertainties (according to GUM) were established. The reference values were established mainly by isotope dilution mass spectrometry (IDMS) as a primary method of measurement, and values traceable to the SI were obtained. The four elements that could not be certified by IDMS were assigned values by means of other measurement techniques. Results from 201 laboratories from 35 countries and four continents were evaluated against the reference values and the comparability between the laboratories is presented graphically.     

Certification of reference materials for Cd, Cr, Hg and Pb in polypropylene

Two reference materials, at relatively low and high concentrations (GBW08404 and GBW08405), for analysis of the mass fractions of Cd, Cr, Hg and Pb in polypropylene were developed. The reference materials were prepared by doping blank polypropylene base material with Cd, Cr, Hg and Pb in the form of oxides, salts or pigments. Homogeneity and stability studies were performed by inductively coupled plasma mass spectrometry. The certification of the four analytes was carried out by isotope-dilution mass spectrometry (IDMS) with microwave-assisted digestion. Combined uncertainties were calculated from the IDMS uncertainty evaluation budget and the uncertainty of the homogeneity. The mass fractions of Cd, Cr, Hg and Pb of the two certified reference materials (CRMs) were from 8 to 1,000 mg kg⁻¹. The two samples were also used in an interlaboratory comparison scheme in which National Institute of Metrology, China, National Metrological Institute of Japan and Korea Research Institute of Standards and Science participated. The agreement of the comparison results proved that the certification procedure of the CRMs is valid and that the certified values of Cd, Cr, Hg and Pb are accurate and reliable.     

Determination of heavy metals (Pb, Cd, Cu, Zn, Cr) in sedimentary reference materials with IDMS: total concentration and aqua regia soluble portion

Summary The total concentration and the aqua regia soluble portion of traces of Pb, Cd, Cu, Zn, and Cr are determined with isotope dilution mass spectrometry (IDMS) in three different types of sediments using a thermal quadrupole instrument (THQ). The results are compared with those obtained by other methods during a certification project to establish these sediments (BCR 277, BCR 280, BCR 320) as standard reference materials. The IDMS (THQ) results are in good agreement with the preliminary certification values and the results of two other laboratories, which applied IDMS using magnetic sector field mass spectrometers. Significant differences between the different analytical methods were found for the total Pb concentration, which could be explained by adsorption and coprecipitation effects during the chemical pretreatment of samples. Using aqua regia instead of HF/HNO₃ for the decomposition of sediments, only 65%–95% of the total Pb and 60%–90% of the total Cr could be dissolved. On the other hand, only a small or negligible portion of Zn, Cd, and Cu could not be dissolved by aqua regia. The IDMS values for the aqua regia soluble Cr portion are significantly higher compared to the results of other methods. This can be explained by adsorption effects.

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Bestimmung von Schwermetallen (Pb, Cd, Cu, Zn, Cr) in sedimentären Standard-Referenzmaterialien mit massenspektrometrischer Isotopenverdünnungsanalyse: Totalgehalt sowie in Königswasser löslicher Anteil

     

Contribution to the certification of B,Cd, Cu,Mg and Pb in a synthetic water sample,by use of isotope-dilution ICP-MS,for Comparison 12 of the International Measurement Evaluation Programme

The contribution of the Institute for Reference Materials and Measurements to the certification of the B, Cd, Cu, Mg, and Pb content of a synthetic water sample used in Comparison 12 of the International Measurement Evaluation Programme (IMEP-12) is described. The aim of the IMEP programme is to demonstrate objectively the degree of equivalence and quality of chemical measurements of individual laboratories on the international scene by comparing them with reference ranges traceable to the SI (Système International d'Unités). IMEP is organized in support of European Union policies and helps to improve the traceability of values produced by field chemical measurement laboratories. The analytical procedure used to establish the reference values for the B, Cd, Cu, Mg, and Pb content of the IMEP-12 sample is based on inductively coupled plasma-isotope-dilution mass spectrometry (ICP-IDMS) applied as a primary method of measurement. The measurements performed for the IMEP-12 study are described in detail. Focus is on the element boron, which is particularly difficult to analyze by ICP-MS because of potential problems of low sensitivity, high mass discrimination, memory effects, and abundance sensitivity. For each of the certified amount contents presented here a total uncertainty budget was calculated using the method of propagation of uncertainties according to ISO (International Organization for Standardization) and Eurachem guidelines. For all investigated elements with concentrations in the low micro g kg(-1) and mg kg(-1) range (corresponding to pmol kg(-1) to the high micro mol kg(-1) level), SI-traceable reference values with relative expanded uncertainties ( k=2) of less than 2 % were obtained.     

The interlaboratory comparison "IMEP-19 trace elements in rice"—a new approach for measurement performance evaluation

The aim of 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. IMEP-19 focused on measurements of trace elements in rice aiming to support the Commission Regulation (EC) No. 466/2001 on maximum levels for certain contaminants in foodstuff. Measurement results for the elements Cd, Cu, Pb and Zn were reported by 267 field laboratories involved in food analysis from 43 countries. Performance criteria for the evaluation of the reported measurement results in IMEP-19 are suggested. The chosen performance indicators not only take into account the deviation of the reported measurement value from the certified reference value, but also set criteria for maximum and minimum acceptable uncertainty. The IMEP-19 participants' performance is reviewed by means of using new simple graphical tools, called "Naji plots".     

Interlaboratory study of trace and other elements in the iaea powdered human hair reference material,HH-1

A powdered intercomparison material for trace element studies was prepared from human scalp hair and distributed to more than 100 laboratories of which 66 reported results for altogether more than 40 elements. By statistical evaluation of these data certified concentration values were derived for 20 elements, namely As, Au, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, Mg, Mn, Na, Pb, S, Sb, Se, Sr and Zn. The data also made it possible to compare different methods of analysis and to judge the value of different levels of experience on the part of the analyst concerned; these comparisons are presented here with special reference to the elements As, Cd, Hg, Pb and Sb.     

The IRMM – International Measurement Evaluation Programme,IMEP

 The aim of the International Measurement Evaluation Programme (IMEP) is to give an objective picture of the state-of-the-practice (SoP) of chemical measurements in field laboratories by comparing them to a reference range that contains a value that is as traceable to the SI system of measurements (in this case to the Avogadro Constant, one of the best realizations of the mole so far), as can presently be achieved, but which in any case is independent of human or political decision. Thus, a large-scale field test has been made to realize (international) comparability of these measurements by providing them with an independent scientific common basis. In the third measurement round, IMEP-3, ten trace elements, B, Ca, Cd, Cu, Fe, K, Li, Pb, Rb and Zn were measured in a synthetic and in a natural water by about 155 participating laboratories using their routine methods. The (coded) results are graphically reported and compared to certified reference values, established by IRMM and NIST, using isotope specific methods (isotope dilution mass spectrometry and neutron activation analysis), wherever possible. One of these methods (IDMS) has recently been defined as a primary method of measurement by the Consultative Committee on Amount of Substance (Comité Consultatif pour la Quantité de Matière: CCQM) in its founding meeting in April 1995 at BIPM, Paris. Results indicate a spread of more than ±50%, asymmetrically distributed around the reference range, although the declared accuracy was 5–10%. Self-assessment by participants of their analytical capabilities does not show a high correlation between a self-rating ("more experienced" or "less experienced") and actual performance. In the way they have been applied, all methods seem to produce results of approximately the same quality. There is little reduction in the spread of the measurements if the results obtained for one element in the natural water B are divided by the results obtained for the same element in the synthetic water A (which was unknowingly, a reference material). Index entries International measurement evaluation programme (IMEP).     

INAA and PIXE for the determination of the contents of extractable sediment

The three-stage BCR sequential step reference extraction procedure was applied to the reference material BCR CRM 601, especially developed for fractionation studies. Extracted fractions were analyzed for Cr, Ni, Zn, Cd, and Pb, by k ₀-standardized instrumental neutron activation (k ₀ INAA) and proton induced X-ray emission (PIXE), and flame atomic absorption spectrometry (FAAS). Sample preparation procedures were developed for both k ₀ INAA and PIXE techniques, related to the evaporation of the solutions in order to get solid samples for neutron and proton irradiation. Quality control was assessed by intercomparison of the analytical results obtained by the applied techniques, which included results for a few certified reference materials. In the extracted fractions, chromium concentration was not determined accurately by both nuclear techniques. Concerning Cd, Ni, Pb, and Zn, the results were in general in good agreement with the certified values and FAAS. Some incomplete separation of the residue might have occurred.     

Simultaneous quantification of 17 trace elements in blood by dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS) equipped with a high-efficiency sample introduction system

A quadrupole inductively coupled plasma mass spectrometer (Q-ICP-MS) equipped with a dynamic reaction cell (DRC) and coupled with a desolvating nebulization system (APEX-IR) was employed to determine 17 elements (Al, As, Ba, Cd, Co, Cr, Li, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, V, and Zr) in blood samples. Ammonia (for Al, Cr, Mn, and V) and O₂ (for As and Se) were used as reacting gases. Selection of the best flow rate of the gases and optimization of the quadrupole dynamic bandpass tuning parameter (RPq) were carried out, using digested blood diluted 1 + 9 with deionized water and spiked with 1 μg L⁻¹ of Al, Cr, Mn, V and 5 μg L⁻¹ of As and Se. Detection limits were determined in digested blood using the 3σ criterion. The desolvating system allowed a sufficient sensitivity to be achieved to determine elements at levels of ng L⁻¹ without detriment of signal stability. The accuracy of the method was tested with the whole blood certified reference material (CRM), certified for Al, As, Cd, Co, Cr, Mn, Mo, Ni, Pb, Sb, Se, and V, and with indicative values for Ba, Li, Sn, Sr, and Zr. The addition calibration approach was chosen for analysis. In order to confirm the DRC data, samples were also analyzed by means of sector field inductively coupled plasma mass spectrometry (SF-ICP-MS), operating in medium (m/Δm = 4000) and high (m/Δm = 10,000) resolution mode and achieving a good agreement between the two techniques.     

Certification of the contents of some heavy metals (Cd, Cu, Hg, Ni, Pb and Zn) in three types of soils

Summary The element contents of Cd, Cu, Hg, Ni, Pb and Zn of three types of soil were certified. The preparation, homogeneity and stability are reported. The certified contents as well as values for Co, Cr, Mn and Se and for the aqua regia soluble contents Cd, Cr, Cu, Mn, Ni, Pb and Zn are given.

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Zertifizierung von Schwermetallspuren (Cd, Cu, Hg, Ni, Pb und Zn) in drei Bodenproben

Zusammenfassung In drei verschiedenen Bodenproben wurden die Elementgehalte an Cd, Cu, Hg, Ni, Pb und Zn zertifiziert. Es wird berichtet über die Bereitung, Homogenität und Stabilität. Die zertifizierten Gehalte sowie der Gehalt an Cr, Co, Mn und Se und der Gehalt an königswasserlöslichem Cd, Cr, Cu, Mn, Ni, Pb und Zn werden angegeben.

     

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”.     

Certification of the contents of some heavy metals (Cd, Co, Cu, Mn, Hg, Ni, Pb and Zn) in three types of sewage sludge

Summary The element contents of Cd, Co, Cu, Mn, Hg, Ni, Pb and Zn of three different types of sewage sludge were certified. The preparation, the homogeneity and the stability are reported. The certified contents as well as values for Cr and Se and for the aqua regia soluble contents of Cd, Cr, Co, Cu, Mn, Ni, Pb and Zn are given.

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Zertifizierung von Schwermetallspuren (Cd, Co, Cu, Mn, Hg, Ni, Pb und Zn) in drei Klärschlammproben

Zusammenfassung In drei verschiedenen Klärschlammproben wurden die Elementgehalte an Cd, Co, Cu, Mn, Hg, Ni, Pb und Zn zertifiziert. Es wird berichtet über die Herstellung, Homogenität und Stabilität. Die zertifizierten Gehalte sowie der Gehalt von Cr, Se und der Gehalt an königswasserlöslichem Cd, Cr, Co, Cu, Mn, Ni, Pb und Zn werden angegeben.

     

Development of a simple and fast ultrasound-assisted extraction method for trace element determination in tobacco samples using ICP-MS

The current study describes a simple and fast method for the determination of Ba, Cd, Co, Cr, Cu, Mn, Ni and Pb in tobacco samples. Commercial cigarettes obtained from local market stores were analysed by inductively coupled plasma mass spectrometry (ICP-MS) after ultrasound-assisted extraction in acidic medium, and the results were compared to those obtained following microwave-assisted digestion of the samples. The sonication time was evaluated from 0 to 60 min, and a 30 min extraction time was selected. The concentration of HNO₃ was also optimised at 0.7 mol L^?1. In order to verify the accuracy of the proposed method, a certified reference material was submitted to the same extraction protocol adopted for the samples, and good agreement with the certified values was obtained at a 95% confidence level, except for Co. The extraction of Pb was also semi-quantitative. A total of four tobacco samples were analysed, with concentrations ranging from 0.4 for Cr to 214.6 µg g^?1 for Mn. The proposed method was demonstrated to be fast, sensitive, precise and accurate for the determination of Ba, Cd, Cr, Cu, Mn an Ni and for the semi-quantitative analysis of Co and Pb in tobacco samples.     

Preparation of the bovine liver 12-02-01 reference material and the certification of element contents from an interlaboratory comparison

Summary The preparation of the bovine liver 12-02-01 reference material, its stabilization and homogeneity testing is presented. Evaluation of an interlaboratory comparison in which 31 laboratories took part using several analytical methods is described. From the results of the intercomparison, the contents of the elements Cd, Cu, Hg, Mn, Pb, Se, and Zn were certified, while for the elements Br, Co, Fe, K, Mo, Na, and Rb, information values were derived. Non-recommended values for the elements Ag, As, Ca, Cl, Cr, Cs, La, Mg, S, Sb, Sn, Sr, and V were also evaluated.Denoted as CZIM-liver in the report [23]     

Determination of 24 elements in four algae reference materials by neutron activation analysis and inductively coupled plasma mass spectrometry

Four algae reference materials, IAEA-391, 392, 393 and IAEA-140, prepared by the International Atomic Energy Agency for intercomparison under different preparation conditions were analyzed for 24 elements. Conventional neutron activation analysis (NAA) was used to determine Al, Ca, Cl, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Sb, V and Zn and epithermal NAA using BN and Cd as shielding material for I, Br, As, Ni, Mo and Cd. Inductively coupled plasma mass spectrometry (ICP-MS) as a complementary and comparative method was applied to determine Pb, Sn, Ni, Sr, Rb, As, Co, Cr, Cu, Mn, V, Mo and Zn. Two analytical quality control standard reference materials IAEA-V-10 (hay powder) and IAEA-331 (spinach) were analyzed simultaneously with real samples. The results agree quite well with each other and with the certified values.     

Planning and certification of new multielemental reference materials for research in antarctica

The adoption of the principles of Good Laboratory Practice (GLP) and the implementation of the ensuing procedures for quality assurance (QA) and quality control (QC) of analytical determinations are nowadays deemed essential to the achievement of sound, credible and comparable experimental information. This is certainly also applicable to research projects currently being carried out in the antarctic continent, in particular as regards investigations on global change phenomena. Worldwide investments made so far in this field do require in fact that reliability of data be optimized so as to allow for a harmonized assessment of ongoing trends. In this context the Italian National Programme for Research in Antarctica has recently launched a project for the preparation of new multielemental certified reference materials (CRMs) to be used for QC of analyses performed on environmentally significant materials. The suitability of CRMs to verify the accuracy of experimental measurements acknowledgedly depends, among others, on the degree of similarity of their matrix composition and analyte levels to those expected for real samples. From this standpoint three CRMs are planned, namely: i) marine sediment certified for Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn and Zn; ii) ocean water certified for Cd, Cr, Cu, Fe, Hg, Mn, Ni and Pb; iii) krill certified for As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn and Zn. Regarding the first two matrices, amounts of ca. 100 kg and ca. 1001, respectively, have been collected during the IX (1993–1994) antarctic expedition, while krill was taken in the course of the X (1994–1995) campaign. The pretreatment of sediment has been accomplished in terms of homogenization, stabilization and characterization of the preliminary ground mass. Approximately 500 bottles, each containing 75 g of material are now ready for distribution to interested laboratories involved in chemical measurements of antarctic matrices, whereas ocean water and krill will follow at a later stage. Finally, depending on circumstances, also the certification of organochlorine compounds in the same materials will be attempted.     

Certification for trace elements and methyl mercury mass fractions in IAEA-452 scallop (Pecten Maximus) sample

A marine certified reference material (CRM), IAEA-452, prepared with scallop (Pecten maximus) sample was recently produced by the International Atomic Energy Agency (IAEA) and certified for trace elements and methyl mercury (MeHg). The Scallop (Pecten maximus) sample is commonly found and consumed seafood and is also used as bio-indicators for trace metal contamination in marine pollution studies. This paper presents the sample preparation methodology, material homogeneity and stability studies, evaluation of certification campaign results, the assignment of property values and their associated uncertainty. The reference values and associated expanded uncertainty for 9 trace elements (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb and Zn) and MeHg in scallop sample are established. The informative value for one more element (Ni) is also given. The new CRM can be used for the development and validation of analytical methods for determination of trace elements and methyl mercury in seafood and also for quality assurance/quality control purposes.