Variations in the stable isotopic composition of carbon are used in diverse fields, including biology, environmental sciences, food and drug authentication and forensic applications.
Background: This paper describes the preparation, analysis and certification of four frozen human serum certified reference materials (CRMs) containing creatinine and the electrolytes calcium, lithium, magnesium, potassium and sodium. These materials have been prepared to give concentrations of these analytes that cover the currently accepted analytical range. Methods: The analysis of the materials for certification purposes has been carried out using methodology traceable to primary standards, and which is acceptable as a reference method. The certification methods include liquid chromatography-mass spectrometry (LC-MS) with exact-matching isotope dilution calibration (EM-IDMS) for creatinine, inductively-coupled plasma optical emission spectroscopy (ICP-OES), ICP-MS and isotope-dilution inductively-coupled plasma mass spectroscopy (ID-ICP-MS) for the electrolytes. Results: The uncertainties estimated for these certified values include a component from the characterization measurements, as well as contributions from possible inhomogeneity and long-term instability. The certified values have been corroborated by measurements obtained in a major UK External Quality Assessment scheme, which have, with the exception of the determination of creatinine at a particularly low concentration, given excellent agreement. Conclusions: The materials are intended for use by pathology laboratories and manufacturers of in vitro diagnostic (IVD) kits for validation of existing routine methodology to a traceable standard, which will promote harmonization between the different methods, instruments and IVD kits used in these laboratories.
Key comparison CCQM-K45 was performed to demonstrate and document the capability of interested national metrology institutes in the mass fraction of Sn in a food matrix. This comparison was an activity of the Inorganic Analysis Working Group of the Comité Consultatif pour la Qualité de la Matière and was coordinated by LGC (Teddington, UK).The following laboratories participated in this key comparison (alphabetical order).
KRISS (Republic of South Korea)
LGC (UK)
LNE (France)
PTB (Germany)
UME (Turkey)
Good agreement was observed between the reported results of four of the participants. The other participant did not use any HCl during the sample preparation, which can affect the stability of the tin in solution, and its reported value was lower than for the other participants. It was not included in the calculation of the key comparison reference value with the agreement of the NMI concerned. The reference value was calculated as the arithmetic mean of the reported participants' results (excluding one), and is equal to 227.1 mg kg-1, with an expanded uncertainty of 2.4 mg kg-1 (1.1%). The equivalence statements were calculated on this basis.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 (MRA).
Preparation of in-house reference materials (RMs) is an important aspect of light element stable isotope analysis. While some relevant information is available, there is, as yet no clear set of guidelines available covering all aspects of in-house RM production and characterization.
Methods
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