Contribution to the certification of B, Cd, Mg, Pb, Rb, Sr, and U in a natural water sample for the International Measurement Evaluation Programme Round 9 (IMEP-9) using ID-ICP-MS

 The present paper describes the contribution of the Institute for Reference Materials and Measurements to the certification of B, Cd, Mg, Pb, Rb, Sr, and U amount contents in a natural water sample, in round 9 of the International Measurement Evaluation Programme (IMEP-9). The analytical procedure to establish the reference values for B, Cd, Mg, Pb, Rb, Sr, and U amount contents was based on isotope dilution inductively coupled plasma-mass spectrometry used as a primary method of measurement. Applying this procedure reference values, traceable to the SI, were obtained for the natural water sample of IMEP-9. 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 and EURACHEM guidelines. The measurement procedures, as well as the uncertainty calculations are described for all seven elements mentioned above. In order to keep the whole certification process transparent and so traceable, the preparations of various reagents and materials as well as the sample treatment and blending, the measurements themselves, and finally the data treatment are described in detail. Explanations focus on Pb as a representative example. The total uncertainties (relative) obtained were less than 2% for all investigated elements at amount contents in the pmol/kg up to the high μmol/kg range, corresponding to low μg/kg and mg/kg levels. Received: 21 October 1999 / Accepted: 29 January 2000     

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.     

Development of an ICP-IDMS method for accurate routine analyses of toxic heavy metals in polyolefins and comparison with results by TI-IDMS

An inductively coupled plasma isotope dilution mass spectrometric (ICP-IDMS) method was developed as a suitable method - with respect to its sensitivity, precision, accuracy, and time-consumption - for the analysis of toxic heavy metal traces (Pb, Cd, Cr, and Hg) in polyolefins. Results for Pb, Cd, and Cr were compared with those obtained by thermal ionization isotope dilution mass spectrometry (TI-IDMS), which was used as a reference method. Because of its high first ionization potential and its high volatility mercury could not be determined by TI-IDMS. A multi-element spike solution, containing isotopically enriched 206Pb, 116Cd, 53Cr, and 201Hg, was used for the isotope dilution step. Decomposition of the polyolefin samples was carried out with concentrated HNO3 at temperatures of about 300 degrees C in a high pressure asher (HPA). This procedure decomposes polyolefins completely and allows isotopic equilibration between sample and spike isotopes. Detection limits of 16 ng/g, 5 ng/g, 164 ng/g, and 9 ng/g were obtained for Pb, Cd, Cr, and Hg by ICP-IDMS using only sample weights of 0.25 g. In different commercially available polyethylene samples heavy metal concentrations in the range of < 5 ng/g to 4 x 10(3) ng/g were analyzed. Both mass spectrometric methods were applied within the EU project "Polymeric Elemental Reference Material (PERM)" for the certification of two polyethylene reference materials. The ICP-IDMS results agreed very well with those of TI-IDMS which demonstrates the accuracy of the ICP-IDMS method also suitable for routine analyses.     

Development of an ICP-IDMS method for accurate routine analyses of toxic heavy metals in polyolefins and comparison with results by TI-IDMS

An inductively coupled plasma isotope dilution mass spectrometric (ICP-IDMS) method was developed as a suitable method – with respect to its sensitivity, precision, accuracy, and time-consumption – for the analysis of toxic heavy metal traces (Pb, Cd, Cr, and Hg) in polyolefins. Results for Pb, Cd, and Cr were compared with those obtained by thermal ionization isotope dilution mass spectrometry (TI-IDMS), which was used as a reference method. Because of its high first ionization potential and its high volatility mercury could not be determined by TI-IDMS. A multi-element spike solution, containing isotopically enriched ²⁰⁶Pb, ¹¹⁶Cd, ⁵³Cr, and ²⁰¹Hg, was used for the isotope dilution step. Decomposition of the polyolefin samples was carried out with concentrated HNO₃ at temperatures of about 300?°C in a high pressure asher (HPA). This procedure decomposes polyolefins completely and allows isotopic equilibration between sample and spike isotopes. Detection limits of 16 ng/g, 5 ng/g, 164 ng/g, and 9 ng/g were obtained for Pb, Cd, Cr, and Hg by ICP-IDMS using only sample weights of 0.25 g. In different commercially available polyethylene samples heavy metal concentrations in the range of < 5 ng/g to 4 × 10³ ng/g were analyzed. Both mass spectrometric methods were applied within the EU project “Polymeric Elemental Reference Material (PERM)” for the certification of two polyethylene reference materials. The ICP-IDMS results agreed very well with those of TI-IDMS which demonstrates the accuracy of the ICP-IDMS method also suitable for routine analyses.     

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.     

Determination of heavy metal traces in metallic materials with IDMS

Summary Two pure copper samples were analysed for Cr, Ni, Zn, Cd, and Pb with isotope dilution mass spectrometry (IDMS) as a part of a certification campaign of the European Community Bureau of Reference in Brussels. Additionally, one commercially available copper powder was determined for Zn, Cd, and Pb. After dissolution of the sample in aqua regia Pb was separated from the matrix by anodic electrodeposition, the other elements by anion-exchange chromatography. Positive thermal ions were produced in a single-filament ion source using the silica gel technique with phosphoric acid for Zn, Cd, and Pb and with boric acid for Cr and Ni. Most of the heavy metals could be determined with relative standard deviations of about 1% down to the ng/g level. The detection limits were 13 ng/g for Zn, 4 ng/g for Ni, 2 ng/g for Cr, 1 ng/g for Pb, and 0.03 ng/g for Cd. The results were compared with those obtained by another IDMS laboratory and by other methods applied during the certification campaign.

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Bestimmung von Schwermetallspuren in metallischen Werkstoffen mit der massenspektrometrischen IsotopenverdünnungsanalyseTeil 1. Bestimmung von Cr, Ni, Zn, Cd und Pb in reinem Kupfer

     

Certified reference materials—Hay Powder (CRM 129) and Rye Grass (CRM 281)—for the quality control of analysis of animal feed

Analyses of nutritive elements are routinely performed in grass or hay for animal feed in order to improve the state of health and growth of domestic animals. To control the quality of such determinations, the Community Bureau of Reference (BCR) so far has produced two certified reference materials: Hay Powder (CRM 129) and Rye Grass (CRM 281). After a careful preparation procedure of the materials, a homogeneity study and a long-term stability study, the contents of the elements Ca, K, Mg, P, S, Zn, I, N and Kjeldahl-N were certified in CRM 129, whereas CRM 281 was certified for As, B, Cd, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se and Zn. This paper presents the certification exercise and especially concentrates on the elements I, B and Mo as examples of analytical work. Indicative values for Co, Cr, Fe, Cl and Na were also obtained.     

The utilization of modified BCR three-step sequential extraction procedure for the fractionation of Cd, Cr, Cu, Ni, Pb and Zn in soil reference materials of different origins

A modified three-step sequential extraction procedure for the fractionation of heavy metals, proposed by the Commission of the European Communities Bureau of Reference (BCR) has been applied to the Slovak reference materials of soils (soil orthic luvisols, soil rendzina and soil eutric cambisol), which represent pedologically different types of soils in Slovakia. Analyses were carried out by flame or electrothermal atomic absorption spectrometry (FAAS or ETAAS). The fractions extracted were: exchangeable (extraction step 1), reducible-iron/manganese oxides (extraction step 2), oxidizable-organic matter and sulfides (extraction step 3). The sum of the element contents in the three fractions plus aqua-regia extractable content of the residue was compared to the aqua-regia extractable content of the elements in the origin soils. The accuracy obtained by comparing the determined contents of the elements with certified values, using BCR CRM 701, certified for the extractable contents (mass fractions) of Cd, Cr, Cu, Ni, Pb and Zn in sediment following a modified BCR-three step sequential extraction procedure, was found to be satisfactory.     

Honey as a candidate reference material for trace elements.

The feasibility of producing and certifying new certified reference materials (CRMs) for trace elements in honey was investigated. Preliminary steps for preparation of candidate materials are performed at the Institute for Reference Materials and Measurements, Joint Research Centre of the European Commission (EC-JRC-IRMM). Two different types of honey, Acacia and Eucalyptus, were tested for determination of 10 trace elements. To each type of honey was added a given amount of high purity deionized water to obtain aqueous solutions with an acceptable degree of homogeneity which would require only minimal manipulation before analysis. Average values obtained for the trace elements by means of inductively coupled plasma-based techniques were as follows (in microg/ kg +/- SD): Acacia honey, As, 1.10+/-0.20; Cd, 0.328+/-0.035; Cr, 1.90+/-0.22; Cu, 67.0+/-5; Fe, 215+/-30; Hg, < 0.75; Mn, 82.1+/-6.2; Ni, 21.0 3.0; Pb, 2.30+/-0.25; Se, 9.10+/-1.2; Zn, 167+/-22; Eucalyptus honey, As, 5.99+/-0.10; Cd, 0.592+/-0.074; Cr, 1.50+/-0.07; Cu, 219 24; Fe, 1008+/-114; Hg, <0.75; Mn, 1009+/-51; Ni, 11.3+/-1.5; Pb, 5.00+/-0.40; Se, 5.60+/-0.91; Zn, 791+/-91. When these 2 pilot materials are ready, the certification project will be launched in full compliance with current rules set by EC-JRC-IRMM. If the project is successful, the new CRMs will be put primarily at the disposal of the National Reference Laboratories for trace elements.     

Development of new reference materials for the determination of cadmium,chromium, mercury and lead in polycarbonate

Reference materials for quantitative determination of Cd, Cr, Hg and Pb in polycarbonate were developed. Reference materials with two concentration level of elements were prepared by adding appropriate amounts of chemicals to a blank polycarbonate base material. It was shown that ten bottles with triplicate analysis are enough to demonstrate the homogeneity of these candidate reference materials. The statistical results also showed no significant trends in both short-term stability test for four weeks and long-term stability test for twelve months. The certification of the four elements was carried out by isotope-dilution-inductively coupled plasma mass spectrometry (ID-ICP-MS) with microwave-assisted digestion. Certification of candidate reference materials in a single laboratory was confirmed with interlaboratory comparison participated by a certain number of well-recognized testing laboratories in Korea. The certified values and expanded uncertainties (k = 2) for the candidate reference material with low level and the one with high level were (51.7 ± 2.1) mg kg⁻¹ Cd, (103.8 ± 2.9) mg kg⁻¹ Cd, (98.8 ± 4.5) mg kg⁻¹ Cr, (1004 ± 49.8) mg kg⁻¹ Cr, (107.4 ± 4.6) mg kg⁻¹ Hg, (1133 ± 50.7) mg kg⁻¹ Hg, (94.8 ± 3.7) mg kg⁻¹ Pb and (988.4 ± 53.6) mg kg⁻¹ Pb, respectively. The reference materials developed in this study demonstrated their suitability for the quality assurance in Cd, Cr, Hg and Pb analysis for the implementation of RoHS Directive.     

Use of INAA in the preparation of a set of soil reference materials with certified values of total element contents

A set of certified Reference Materials was prepared consisting of four natural agricultural soils with normal (n) and elevated (e) levels of element contents: CRM 7001 Light Sandy Soil (n), CRM 7002 Light Sandy Soil (e), CRM 7003 Silty Clay Loam (n), and CRM 7004 Loam (e). In these materials, certified and/or information values of the total contents of the elements As, Ba, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V and Zn, and their fractions extractable by aqua regia, boiling and cold 2M nitric acid were derived from an interlaboratory comparison in which 28 laboratories participated. Highly precise and accurate procedures of instrumental neutron activation analysis (INAA) were employed for homogeneity testing and also for certification of the total element contents. For comparation purposes, NIST SRM-2704 Buffalo River Sediment was analyzed by INAA, as well. The INAA results obtained compared very well with the certified and/or information values for four soil CRMs and also with NIST values for SRM-2704. From this agreement, a very high reliability of the new soil CRMs can be inferred.     

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.     

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.

     

A pilot study on the feasibility of the preparation of a new certified reference material based on the Antarctic Scallop Adamussium Colbecki

As foreseen by the Italian National Programme of Research in Antarctica, a preliminary investigation was performed to ascertain the feasibility of the production of a new Certified Reference Material for trace elements based on the bivalve Adamussium colbecki. The scallops sampled in Antarctica during the 1999–2000 Italian scientific expedition were analyzed by inductively coupled plasma atomic emission spectrometry and high-resolution inductively coupled plasma mass spectrometry for their content in selected trace elements (As, Cd, Cr, Cu, Fe, Hg, Mn, Mo, Ni, V and Zn). The certification campaign will be undertaken on the basis of the findings of this feasibility study in close cooperation with the Institute for Reference Materials and Measurements, Joint Research Centre of the European Commission.     

Certified reference material (CRM 414) for the quality control of trace element analysis in plankton

Summary Analyses of plankton are performed by a number of organisations to investigate the transfer and uptake of toxic elements along the trophic chain and to monitor the levels of contamination of different aquatic environments. In order to obtain reliable transfer functions in environmental models or to use plankton as an indicator organism for the assessment of environmental pollution, these analyses should give accurate results. As accuracy requires quality control and the application of certified reference materials (CRMs), a certification campaign has been conducted by the Community Bureau of Reference (BCR). A plankton material was collected in a freshwater pond, lyophilised, homogenised and bottled and its homogeneity and long-term stability were verified. The material (CRM 414) was analysed by a group of 15 selected laboratories having given proof of their adequate QC and using different analytical methods. The contents of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se, V and Zn are certified. This paper presents the certification work performed.     

High-throughput determination of seven trace elements in food samples by inductively coupled plasma-mass spectrometry

A method was developed for high-throughput determinations of 7 elements in food samples, namely antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and tin (Sn). The samples were digested by closed-vessel microwave-assisted digestion using concentrated nitric acid (HNO3) as the medium, followed by microwave- assisted evaporation to concentrate the sample solutions before dilution to the desired volume. The microwave-assisted evaporation procedure effectively reduced the final acid concentration to around 8% before analysis by inductively coupled plasma-mass spectrometry (ICP-MS). This reduction allows determination by ICP-MS to proceed without further sample dilution, which would affect the detection limit. The method was validated, and method recoveries for As, Cd, Cr, Pb, and Hg were within the certified ranges of the chosen certified reference materials. Recoveries of the 7 elements from spiked samples ranged from 93.1 to 103.6%. The standard uncertainties of precision for the 7 elements were between 3.1 and 4.3%. Interlaboratory comparison studies for As, Cd, and Pb gave z-scores ranging from -0.2 to 0.3.     

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     

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