Production and certification of four frozen human serum certified reference materials containing creatinine and electrolytes

Abstract

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.

The Need for Standardization of Tacrolimus Assays

“…The EM-IDMS calibration procedure is routinely used at LGC to assign reference values to certified reference materials (CRMs) (7 ). An EM-IDMS-based method has been developed at LGC for the characterization of a candidate tacrolimus in whole-blood CRM.…”

Determination of lithium in human serum by isotope dilution atomic absorption spectrometry

“…On the top left corner of each spectrum, schematic representation of the isotope amount fractions of Li is provided and comparable with those obtained with ID-AAS and ID-MS procedures, which afford uncertainties ranging between 0.006 and 0.015 mmol L −1 [15,26,27]. The higher-order, traceability, and commutability of the studied certified reference materials assure their representability as clinical human serum samples [28][29][30]. For all these, ID-HR-CS-GFAAS can be envisaged as a metrological procedure for a fast, simple, and low-cost determination of Li in human serum.…”

High-Accuracy Determination of Potassium and Selenium in Human Serum by Two-Step Isotope Dilution ICPMS

“…It has absolute measurement properties, and the values obtained can be traced directly to the international basic unit of the mass, namely, mole. In conventional detection methods, factors such as the loss of tested elements during the pretreatment process of the sample, the matrix effects, and the instrument noises may affect the accuracy of the tests negatively, which can be eliminated to a great extent by the isotope dilution method [2][3][4][5]. In Isotope Dilution ICPMS, the isotope abundance ratio rather than the concentration of the sample is measured.…”