Search

Mercury is a toxic element of particular concern for the environment and human health, but its accurate analysis is challenging due to its unique physical and chemical properties. In order to enhance the quality and traceability of measurements, a proficiency testing (PT) program (MFDS-PT-101FM-2017) for mercury in oyster tissue has been conducted by the Ministry of Food and Drug Safety (MFDS) of Korea. A majority of the participating laboratories have used commercial mercury analyzers based on thermal decomposition amalgamation atomic absorption spectrometry (TDA–AAS). Good agreement between the participants’ results and the reference value (RV) was observed, where the RV is traceable to the International System of Units and verified for international equivalence. The results of this PT program support the participating laboratories in demonstrating their competence in quantitative analysis, and show the potential of commercial TDA–AAS systems for accurate mercury analysis.

Main text CCQM-K143 is a key comparison that assesses participants' ability to prepare single element calibration solutions. Preparing calibration solutions properly is the cornerstone of establishing a traceability link to the International System of Units (SI), and therefore should be tested in order to confirm the validity of CCQM comparisons of more complex materials. CCQM-K143 consisted of participants each preparing a single copper calibration solution at 10 g/kg copper mass fraction and shipping 10 bottled aliquots of that solution to the coordinating laboratory, the National Institute of Standards and Technology (NIST). The masses and mass fraction for the prepared solutions were documented with the submitted samples. The solutions prepared by all participants were measured at NIST by high performance inductively coupled plasma optical emission spectroscopy (HP-ICP-OES). The intensity measurements for copper were not mapped onto values of mass fraction via calibration. Instead, ratios were computed between the measurements for copper and simultaneous measurements for manganese, the internal standard, and all subsequent data reductions, including the computation of the KCRV and the degrees of equivalence, were based on these ratios. Other than for two participants whose measurement results appeared to suffer from calculation or preparation errors, all unilateral degrees of equivalence showed that the measured values did not differ significantly from the KCRV. These results were confirmed by a second set of ICP-OES measurements performed by the Physikalisch-Technische Bundesanstalt (PTB). CCQM-K143 showed that participants are capable of preparing calibration solutions starting from high purity, assayed copper metal. Similar steps are involved when preparing solutions for other elements, so it seems safe to infer that similar capabilities should prevail when preparing many different, single-element solutions. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Liver plays a major role in metabolism and acts as a source of energy for the body by storing glycogen. With the growing interest and investigation in the biological effects in recent years, it is important and necessary to develop accurate and comparable analytical methods for elements in bio-samples. It has, however, been 10 years since the tissue sample (bovine liver) of CCQM-K49 key comparison. The purpose of CCQM-K145 is to ensure the comparable and traceable measurement results for essential and toxic elements such as P, S, Zn, Mn, Ni, Mo, Sr, Cr, Co, Pb, As and Hg in bovine liver among NMIs and other designated measurement bodies worldwide. The comparison was agreed by IAWG as 6th IAWG Benchmarking Exercise with Zn and Ni as exemplary elements at the meeting in Korea in the early October 2016. The results of CCQM-K145 are expected to cover the measurement capability and support CMCs claiming for inorganic elements in the similar biological tissue materials and food samples. 30 NMIs and DIs registered in CCQM-K145. With respect to the methodology, a variety of techniques such as IDMS, ICP-OES, ICP-MS(non-ID), AAS and NAA were adopted by the participants. For Zn, Ni, Sr, Pb and Hg measurements, most participants chose ID-ICP-MS method, which showed the better performance in terms of consistency and reliability of the measurement results. In aspect of the traceability for the measurement results in CCQM-K145, most participants used their own (in house) CRMs or other NMI's CRMs to guarantee trace to SI unit. Most participants used similar matrix CRMs for quality control or method validation. Base on different statistic way to calculate the reference mass fraction values and associated uncertainties for each measurand, removal of the suspected extreme values, and discussion at the IAWG meetings, the median values are proposed as the KCRV for Zn, Ni, Mn, Mo, Cr, Pb and Hg; the arithmetic mean values are proposed as the KCRV for P, S, Sr, Co and As. In general, the performances of the majority of CCQM-K145 participants are very good, illustrating their measurement capabilities for Zn, Ni, P, S, Mn, Mo, Sr, Cr, As, Co, Pb and Hg in a complex biological tissue matrix. Bovine liver contains many kinds of nutrients and microelements, it can be regarded as a typical representative material of biological tissue and food. In CCQM-K145, the analytes involved alkali metals and transition elements, metalloids / semi-metals and non metals with a range of mass fraction from mg/g to μg/kg. CCQM-K145 also tested the ability of NMIs/DIs to determine elements that were easy to be lost and polluted, and interfered significantly. The chemical pretreatment methods of samples used in the comparison is suitable for general food and biological matrix samples. A variety of measurement methods used in the comparison represent the main instrumental technology for elemental analysis. Therefore, for supporting CMC claim, CCQM-K145 is readily applicable to measurement of more elements in a wide range of biological materials (including liquids and solids) and meat products. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A paste-type certified reference material (CRM) of tomato was developed for accurate elemental analysis of canned foods. Accurate mass fractions of cadmium (Cd), lead (Pb), and tin (Sn) in the tomato paste CRM were determined by isotope dilution inductively coupled plasma mass spectrometry. The certified values and their expanded uncertainties (k=2 at approximately 95% level of confidence) for Cd, Pb, and Sn were (0.297 ± 0.015) mg/kg, (0.213 ± 0.010) mg/kg, and (221.2 ± 9.5) mg/kg, respectively. Homogeneity of the CRM was 0.3%, 1.8%, and 0.2% for Cd, Pb, and Sn, respectively, which were estimated using the relative standard deviation of the measurement results of 10 separate sample bottles from one batch of the CRM. Major contributions to the measurement uncertainties for Cd and Sn were the uncertainties of the isotope ratios of Cd and Sn in the sample and the elemental standards. The uncertainty for Pb was mainly affected by sample homogeneity. Stability tests were conducted for 6 and 12 months at −20, 4, and 25°C, and the storage temperature for the CRM was determined to be −20°C. To investigate long-term storage, the mass fractions of Cd, Pd, and Sn in the CRM were re-determined after storage for 7 years. The results were in good agreement with the certified results implying that this CRM is stable for 7 years if kept at an appropriate storage condition with vacuum packaging the amber glass bottles in aluminum-coated polymer bag.

The Asia Pacific Metrology Program (APMP) and Asia Pacific Laboratory Accreditation Cooperation (APLAC) joint proficiency testing (PT) program was established to improve the ability of quantitative analysis and enhance the quality of the PT program through a better regional linkage between the national metrology institutes (NMIs) and the accreditation bodies (ABs) in the Asia-Pacific region. The first APMP-APLAC joint PT was carried out to quantify hazardous elements Cd and Pb in kimchi cabbage powder, where a candidate certified reference material (CRM) was used as the PT material. A total of 83 laboratories from 37 countries registered, of which 73 laboratories submitted their results. Certified reference values (RVs) provided by Korea Research Institute of Standards and Science (KRISS) were used to evaluate the z -scores ( z ) of participants' results. This program confirms significant importance of the use of metrologically traceable RVs as PT assigned values for rigorous evaluation and reliable assessment.

In the present study, we have developed an exact matrix-matching inductively coupled plasma-optical emission spectroscopy (ICP-OES) as a low-cost alternative to the isotope dilution inductively coupled plasma-mass spectrometry (ICP-MS) method for accurate and precise measurements of nutrient elements K and Cu in infant formula. In spite of its high precision and accuracy, ICP-OES analysis of complex samples was not reliable due to biases originating from various matrix effects. The elaborated exact matrix-matching approach tested here demonstrated its potential to minimize biases due to matrix mismatch. The exact matrix-matching ICP-OES method was successfully validated by comparing the results with those from an isotope dilution ICP-MS method. Because the model provides reliable results without significant loss of precision, it will be an excellent choice for major element analysis in a complex sample, especially when isotope dilution is not applicable due to the lack of alternative isotopes or the high cost of enriched isotopes.

Accurate measurement of hazardous elements in cosmetics is considerably important in response to cosmetic safety issues. A sample preparation method using microwave-assisted acid digestion combined with double isotope dilution inductively coupled plasma/mass spectrometry (ID ICP-MS) was used for the certification of the hazardous elements, Cd, Hg and Pb, in cosmetic powder samples. The HF-free sample preparation method was validated and applied to analyse Cd and Pb in cosmetic powder. The Hg content in the sample was determined by employing a fast valve sample introduction system to resolve the severe memory effect in Hg analysis. Homogeneity and stability were also evaluated. The certified values of Cd, Hg and Pb were (24.8 ± 1.3) mg kg−1, (0.648 ± 0.065) mg kg−1 and (24.55 ± 0.31) mg kg−1, respectively. The relative combined standard uncertainty was 2.7% for Cd, 5.1% for Hg and 0.62% for Pb. The detailed procedure for certification and evaluation of the associated uncertainty is also presented. The proper use of the developed CRM for quality control and method validation in testing laboratories and the cosmetic industry is expected to significantly improve the reliability and quality of test results for hazardous elements in cosmetics, thereby contributing to cosmetic safety.

A certified reference material (CRM), NMIJ CRM 7203-a, was developed for the elemental analysis of tap water. At least two independent analytical methods were applied to characterize the certified value of each element. The elements certified in the present CRM were as follows: Al, As, B, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Rb, Sb, Se, Sr, and Zn. The certified value for each element was given as the (property value ± expanded uncertainty), with a coverage factor of 2 for the expanded uncertainty. The expanded uncertainties were estimated while considering the contribution of the analytical methods, the method-to-method variance, the sample homogeneity, the long-term stability, and the concentrations of the standard solutions for calibration. The concentration of Hg (0.39 μg kg-1) was given as the information value, since loss of Hg was observed when the sample was stored at room temperature and exposed to light. The certified values of selected elements were confirmed by a co-analysis carried out independently by the NMIJ (Japan) and the KRISS (Korea).

The CCQM-K97 key comparison was organized by the inorganic analysis working group (IAWG) of CCQM as a follow-up to completed pilot study CCQM-P96 and P96.1 to test the abilities of the national metrology institutes to accurately quantitate the mass fraction of arsenobetaine (AsB) in standard solution and in fish tissue. A pilot study CCQM-P133 was parallelized with this key comparison. National Institute of Metrology (NIM), China and National Metrology Institute of Japan (NMIJ) acted as the coordinating laboratories. Six NMIs participated in CCQM-K97 and two institutes participated in CCQM-P133, and all of them submitted the results. Some NMIs submitted more than one results by different methods. The results were in excellent agreement with each other, and obviously better than those of previous P96 and P96.1. Therefore the calibrant which each NMI used was comparable. It shows that the capabilities of some of the participants have been improved after the previous pilot studies. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

An isotope dilution liquid chromatography tandem mass spectrometry (ID LC-MS/MS) method has been developed and applied to the determination of arsenobetaine (AsB, (CH3)3 AsCH2COO −) from oyster candidate certified reference material (CRM). The exact matching isotope dilution approach was adopted for accurate determination of AsB using C2-labeled AsB as an internal standard. Efficiencies of different AsB extraction methods were evaluated using a codfish reference material and a simple sonication method was selected as the method of choice for the certification of the oyster candidate CRM. The hydrophilic interaction liquid chromatography (HILIC) combined with electrospray ionization tandem mass spectrometry (ESI/MS/ MS) in selected reaction monitoring (SRM) mode was optimized for adequate chromatographic retention and robust quantification of AsB from codfish and oyster samples. By analyzing 12 subsamples taken from each 12 bottles systematically selected from the whole oyster CRM batch, the certified value of AsB was determined as 6.60 mg·kg ± 0.31 mg·kg and it showed excellent between-bottle homogeneity of less than 0.42%, which is represented by relative standard deviation of 12 bottles from the CRM batch. The major source of uncertainty was the certified value of the AsB standard solution.

A certified reference material (CRM), KRISS CRM 108-10-003, has been developed for analysis of acrylamide in potato chips, as a representative of carbohydrate-rich food cooked in high-temperature oil. The material was prepared by grinding commercially available potato chips to a paste which was then homogenized, bottled in 15-g units, and stored at -70 °C. Certification, homogeneity and stability testing, were carried out by liquid chromatography-isotope-dilution mass spectrometry (ID-LC-MS). A single ID-LC-MS measurement was performed for each of 10 selected units for certification and homogeneity assessment. The mean measurement result for the 10 bottles, 0.455 ± 0.012 mg kg(-1), was assigned as the certified value of the CRM. The between-bottle homogeneity was 0.8% of the certified value. The within-bottle homogeneity, tested by measuring three replicate sub-samples from each of three randomly selected bottles, was similar to the between-bottle homogeneity. The stability of the CRM under storage conditions (-70 °C) was tested for 21 months and no change in the acrylamide content was observed within the measurement uncertainty. Stability of the CRM at -20 °C (storage at user's site) and room temperature (for regular use and transportation) was also tested. Also presented is the newly designed procedure for evaluating the uncertainty of the certified value for the characterization scheme used in this study.

A method is described for the determination of dibutyltin (DBT) in sediment by isotope dilution using liquid chromatography inductively-coupled plasma/mass spectrometry (LC-ICP/MS). To achieve the highest accuracy and precision, special attentions are paid in optimization and evaluation of overall processes of the analysis including extraction of analytes, characterization of the standards used for calibration and LC-ICP/MS conditions. An approach for characterization of natural abundance DBT standard has been developed by combining inductively-coupled plasma/optical emission spectrometry (ICP/OES) and LC-ICP/MS for the total Sn assay and the analysis of Sn species present as impurities, respectively. An excellent LC condition for separation of organotin species was found, which is suitable for simultaneous DBT and tributyltin (TBT) analysis as well as impurity analysis of DBT standards. Microwave extraction condition was also optimized for high efficiency while preventing species transformation. The present method determines the amount contents of DBT in sediments with expanded uncertainty of less than 5% and its result shows high degree of equivalence with reference values of an international inter-comparison and a certified reference material (CRM) within stated uncertainties.

The CCQM-K96.1 key comparison was a subsequent bilateral comparison to the CCQM-K96 'Determination of amount content of dichromate'. The comparisons were organized jointly by the inorganic analysis and electrochemical analysis working groups of the CCQM to test the abilities of the metrology institutes to measure the content amount of dichromate. The NIM China has obtained unsatisfactory results from the CCQM-K96. The NIM requested a bilateral comparison to demonstrate its capability after improvement. The KRISS acted as the coordinating laboratory and served as a link to the reference value of CCQM-K96. Both participants used high-accuracy constant current coulometry. A good agreement of the results was observed. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The key comparison CCQM-K96 was organized jointly by the inorganic and electrochemistry working groups of CCQM to test the abilities of the metrology institutes to measure the amount content of dichromate. Slovak Institute of Metrology with help of KRISS acted as the coordinating laboratories. Eight NMIs took part in the comparison. All participants used high accuracy constant current coulometry. Good agreement of the results was observed. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

This key comparison (KC), CCQM-K73, was performed to demonstrate the capability of the participating National Metrology Institutes (NMIs) to measure the amount content of H+, νH+, in an HCl solution with a nominal νH+ of 0.1 mol kg−1. The comparison was a joint activity of the Electrochemical Working Group (EAWG) and Inorganic Analysis Working Group (IAWG) of the CCQM and was coordinated by NIST (USA) and CENAM (Mexico). The agreement of the results was not commensurate with the claimed uncertainties of the subset of participants that claimed small uncertainties for this determination. A workshop on technical issues relating to the CCQM-K73 measurements was conducted at the joint IAWG-EAWG meeting at the Bureau International des Poids et Mesures (BIPM), Paris (Sevres) in April 2010. Several possible sources of bias were investigated, but none could explain the observed dispersion among the participants' results. In the absence of a specific cause for the dispersion, the IAWG and EAWG decided to assign a Key Comparison Reference Value, KCRV, and standard uncertainty of the KCRV, uKCRV, based on the DerSimonian–Laird statistical estimator. The uKCRV is dominated by the between-laboratory scatter of results in CCQM-K73. The uncertainty estimates from the participants with the lowest reported uncertainties remain unsupported by this KC. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The key comparison CCQM-K34 was organized jointly by the inorganic and electrochemistry working groups of the CCQM as a follow-up to the pilot study CCQM-P36 to test the abilities of the metrology institutes to measure the amount content of acid in solid weak acids. The Slovak Institute of Metrology acted as the coordinating laboratory, and seven NMIs expressed interest in participation. All participants used constant current coulometry at different levels of sophistication. In general very good agreement of the results was observed; some possible problems were highlighted. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM.