Preparation and preliminary certification of two new Polish CRMs for inorganic trace analysis

Preparation and characterization of two new reference materials of biological origin, namely: Tea Leaves (INCT-TL-1) and Mixed Polish Herbs (INCT-MPH-2) is described. The raw materials were ground in an agate ball mill, sieved through a nylon sieve, collecting fraction of particle size: Æ£67 ·m, and carefully homogenized. Preliminary homogeneity testing by XRF method and final checking of homogeneity by NAA after distribution of the materials into containers revealed that they are sufficiently homogeneous at least for sample size ≥100 mg. Both materials were prepared in amounts exceeding 40 kg and certified on the basis of a worldwide interlaboratory comparison, in which 109 laboratories from 19 countries participated. The method of data evaluation leading to assignment of certified values was essentially the same as that used previously in this Laboratory, but supplemented by additional data from the analysis of a CRM which was sent to the participants and analyzed by them along with the candidate reference materials. In addition the results for a few elements by very accurate developed methods in this Laboratory were obtained and used to support the certification process. Analytical uncertainties and stability uncertainties were quantified to arrive at combined uncertainties of the certified values. So far 18 elements in INCT-TL-1 and 21 in INCT-MPH-2 could be certified.     

Certification of trace and major elements and methylmercury concentrations in a macroalgae (Fucus sp.) reference material, IAEA-140

A marine reference material, IAEA-140, prepared with a macroalgae (Fucus sp.) was recently produced by the International Atomic Energy Agency and certified for trace and major elements and for methylmercury (MeHg). Certification of this material was achieved as an outcome of an international analytical intercomparison study which resulted in 116 independent sets of results reported by participants from 54 countries. The statistical evaluation of the collected data and the criteria used for assignment of the mean and uncertainty values are described. The analysis of data allowed to certify concentration values for 24 elements and MeHg, and to provide information values for another 10 elements. Regarding the elements which could be given certified values, between two and eight different instrumental methods were used to measure metal concentrations, and four independent analytical procedures were used to measure MeHg concentrations. In order to assess the results of the certification procedure, a comparison was made between the certified values obtained from the world-wide intercomparison results and the values obtained from a small subgroup of well-qualified laboratories. The means and 95% confidence intervals for reference values obtained by the two methods are similar for most elements showing that the usual method of certification used by the IAEA, based on large groups of participants, is indeed pertinent.     

Certification of trace and major elements and methylmercury concentrations in a macroalgae (Fucus sp.) reference material, IAEA-140

A marine reference material, IAEA-140, prepared with a macroalgae (Fucus sp.) was recently produced by the International Atomic Energy Agency and certified for trace and major elements and for methylmercury (MeHg). Certification of this material was achieved as an outcome of an international analytical intercomparison study which resulted in 116 independent sets of results reported by participants from 54 countries. The statistical evaluation of the collected data and the criteria used for assignment of the mean and uncertainty values are described. The analysis of data allowed to certify concentration values for 24 elements and MeHg, and to provide information values for another 10 elements. Regarding the elements which could be given certified values, between two and eight different instrumental methods were used to measure metal concentrations, and four independent analytical procedures were used to measure MeHg concentrations. In order to assess the results of the certification procedure, a comparison was made between the certified values obtained from the world-wide intercomparison results and the values obtained from a small subgroup of well-qualified laboratories. The means and 95% confidence intervals for reference values obtained by the two methods are similar for most elements showing that the usual method of certification used by the IAEA, based on large groups of participants, is indeed pertinent.     

电感耦合等离子体质谱法对GSS系列土壤及沉积物标准物质中多种元素的定值

介绍对10种GSS系列土壤及沉积物标准物质中多种元素进行定值的方法和结果，采用模拟土壤元素天然组成比值的校正溶液，对元素间的基体干扰具有明显的抑制作用，利用115In-103Rh双内标元素校正系统，可有效地抑制分析信号的动态漂移，建立了电感耦合等离子体质谱法对土壤及沉积物标准的物质中多种元素定值的方法，用该方法对GSS－4，GSS－5，GSS－8及GSD－9共4种土壤标准物质进行测定，绝大部分元素的测定结果与标准值的相对误差小于10％，相对标准偏差小于10％，对GSS－10－GSS－16，AMS－1，BEM及DMS－1共10种土壤及沉积物待定值标准物质进行定值，绝大部分元素测定结果的相对标准偏差小于10％。     

Radiochemical neutron-activation analysis of uncertified ultra-trace rare earth elements in two biological certified reference materials

Radiochemical neutron activation analysis (RNAA) has been used for the determination of eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu) in two Chinese certified reference materials (CRM), GBW 08503 (wheat powder) and GBW 09101 (human hair). These determinations are important for possible certification of the above mentioned ultra-trace elements, so far not certified. A simple one-step (REE)F3 precipitation was used. Chemical yields were determined for all relevant elements by means of tracer experiments. The two CRM were also analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) to compare the merits and draw-backs of these two major trace analytical techniques for these particular elements. RNAA was proven to be a reliable technique for ultra-trace analysis, especially in the certification of some ultra-trace elements.     

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     

Input of missing trace elements in some IAEA/NBS biological certified reference materials using INAA

IAEA and NBS biological certified reference materials have been analyzed by instrumental neutron activation analysis and concentration of 17 elements was determined. The elements determined were either completely missing or their certified values were not given in the original compilations. For quality assurance of our work, a comparison of data on missing trace elements in some of the CRMs has been presented. It seems that second round of analysis for the certification of these elements would be useful.     

Thermal standards from the laboratory of the government chemist

The Laboratory of the Government Chemist (LGC) is a focal point for the production, analysis and certification of reference materials. Within the field of thermal analysis the LGC is concerned with the development of purity standards and materials certified for enthalpy of fusion and melting point. For some time the LGC has been concerned with the significant differences in purity data which can be produced by the different manufactures' differential scanning calorimeters. This paper will highlight the initiatives the LGC is undertaking in overcoming this uncertainty in purity measurements through the use of certified thermal standards.     

The certification of a new paint reference material

The use of paint as a coating for toys intended for sale on the European market is controlled by a European Standard (EN 71-3: 1994-European Standard for the Safety of Toys, Part 3—Migration of Elements). This work is the result of a preliminary study organised by the European Commission to produce a new paint reference material which can be used to validate the test methods given in the European Standard. The migration of elements from painted panels and comminuted paint produced by the Laboratory of the Government Chemist, (U.K.) was studied. Several methods were used in this certification exercise and this work reports the recults of neutron activation analysis and inductively coupled plasma mass spectrometry to determine the migration of As, Ba, Cd, Cr, Hg, Pb, Se and Sb into a simulated stomach environment. Replicate extracts obtained from paint samples gave a precision of within 10% for most elements by both analytical techniques for the paint panels and for the comminuted paint sample. This preliminary study has shown that the standard method can provide reproducible results for each of the paint materials studied and indicates that the study should be continued to produce a fully certified paint reference material.     

Certification of the mass fractions of Ca,Cu, Cl,I, Fe,K, Mg,P, Pb,N, Na and Zn in skim milk powder

Analyses of milk and milk products are routinely performed by a number of dairy laboratories to control the quality of these products with regard to e.g. nutritional components and potential exposure to toxic elements. In order to improve and control the quality of such analyses the Community Bureau of Reference (BCR) has organized series of certification campaigns to produce reference material of milk certified for a variety of elements and compounds. The increasing demand is such that the stock of some of these materials is now exhausted. Consequently, the BCR decided to produce a new batch of CRM of skim milk powder certified for its contents of Ca, Cu, Cl, I, Fe, K, Mg, P, Pb, N, Na and Zn (CRM 063R). This material was carefully prepared (spray-drying) and its homogeneity and long term stability was verified. This paper presents the certification work performed.