Metrology In Chemistry Research Articles

International comparisons in the field of measurement of specific adsorption of gases and specific surface area of solids: the optimal amount to ensure calibration and measurement capabilities

Indicators of the accuracy of measurements of the most important characteristics of the structure of porous and dispersed materials - specific adsorption of gases, specific surface area, specific pore volume and pore size – are considered. The performance of sorbents, catalysts and membranes in the chemical and petroleum industries, including the purification of substances and materials, depends on the values of these characteristics. It has been established that for mutual recognition of national standards and certificates of calibrations and measurements of porosity characteristics of solid substances performed by national metrological institutes, it is required to organize and successfully participate in three international key comparisons under the auspices of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology of the International Bureau of Weights and Measures. The results of the participation of national metrology institutes and designated organizations of Germany, China, Japan, Brazil, Turkey and Russia in three international key comparisons in the field of measurements of specific adsorption of gases (nitrogen, argon, krypton) and specific surface area of solids (zeolite, silicon oxides and aluminum) are presented. Carrying out the optimal number of comparisons makes it possible to register in the Key Comparison Database of the International Bureau of Weights and Measures the measuring and calibration capabilities of the national metrological institutes of the participating countries for various matrices in a wide range of measurements of specific adsorption of gases 0.001–25 mol/kg and specific surface area of solids 0.1–1500 m2/g. Based on the results of these three international key comparisons, 18 of broad calibration and measurement capabilities of the Russian participant, the D. I. Mendeleev Institute for Metrology, were entered into the Key Comparison Database; two of these items are currently undergoing examination, including reference materials produced by this institute. A comparative analysis of the results of measurements of the specific surface area of solids using nitrogen and krypton as adsorbates was performed. It has been established that the uncertainty of the measurement results of the specific surface area is significantly less in the case of using krypton as an adsorbate with a specific surface area of less than 1 m2/g, which is due to the higher values of the relative pressure of krypton compared to nitrogen. The use of calibration and testing laboratories in Russia of certified reference materials of sorption properties presented in the Key Comparison Database of the International Bureau of Weights and Measures will ensure metrological traceability in the field of measurements of porosity characteristics.

Characterization of calibration solution certified reference material for polycyclic aromatic hydrocarbons by exact matching isotopic dilution mass spectrometry: a case study from the Brazilian Metrology Institute

Abstract Recertification is a common practice in National Metrology Institutes whenever advances are made in certified reference material (CRM) characterization procedures, which play a key role in metrological traceability. This article compares measurements of 16 priority polycyclic aromatic hydrocarbons (PAHs) in toluene by gas chromatography isotopic dilution mass spectrometry (IDMS) using either an calibration curve or the exact matching approach. The multi-point IDMS calibration curve was used on the original CRM certification and the exact matching approach was carried out on its recertification. The measurement uncertainties by exact matching approach (0.3%–1.0%) were approximately 5 times smaller than those obtained using the calibration curve (1.5%–4.4%) for all PAHs, reducing the uncertainty component due to characterization of PAH CRM. This new characterization study added reliability, increased accuracy and reduced the measurement uncertainty of the Inmetro CRM, with metrological traceability to the International System of Units. The exact-matching isotope dilution is an important technique to value assign organic compounds in CRMs, an action that consolidates the chemical metrology in the Brazilian Metrology Institute.

The Importance of Teaching Metrology for Chemistry Undergraduate Courses

The Chemistry undergraduate courses, in general, aim to train professionals for research, teaching and activities in industry. In all these areas, the statistical treatment of data supported by metrology disciplines has been a decisive boost to consolidate conclusions in Analytical Chemistry. The main objective of this work was to stimulate the teaching of the metrology in the chemistry undergraduate courses in Brazil and Portugal. In this work we present some concepts and practical cases of metrology and statistics, which together guarantee the suitability of analytical measurement results for specific purposes. Knowledge of these concepts is essential for the chemist to act effectively and responsibly, avoiding some pitfalls when processing data in Analytical Chemistry. A supplementary material with Excel spreadsheets is available, containing the statistical treatment of some examples and complementing the discussions in this work. A survey is presented among the most important universities in Brazil and Portugal, from which we can see the lack of teaching these subjects in undergraduate chemistry courses. For this reason, this work recommends a syllabus for creating chemical metrology disciplines in undergraduate chemistry courses. To subsidize this syllabus, an extensive, but not exhaustive, bibliography is indicated.

CCQM-K161 "Anions in Seawater"

Main textAnions or nutrients in seawater are very important targets for oceanographic research and environmental monitoring of contaminations. Quantification of minor and trace anions in seawater has always been a challenge for the extremely high salinity, disparate levels of analyte and matrix ions, and even need to be measured at levels close to the detection limits of the method performance. Evidence of successful participation in formal, relevant international comparisons is needed to support calibration and measurement capability claims (CMCs) made by the national metrology institutes (NMIs) and designated institutes (DIs).The CCQM-K161 Anions in Seawater was organized by the Inorganic Analysis Working Group (IAWG) of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) to assess the abilities of the NMIs and DIs for the accurate determination of minor and trace anions in seawater. The measurands covered chloride (16 mg/g-25 mg/g), sulfate (1 mg/g-4 mg/g), bromide (30 mg/kg-100 mg/kg), nitrate (1 mg/kg-5 mg/kg) and phosphate (60 µg/kg-300 µg/kg). Twelve national metrology institutes and designated institutes participated in this key comparison. Participants were requested to evaluate the mass fractions, expressed in mg/g for chloride and sulfate, mg/kg for bromide and nitrate, and µg/kg for phosphate (as phosphorus) in a mixed natural seawater that was spiked with the phosphate. A variety of techniques including isotope dilution inductively coupled plasma mass spectrometry (IDMS), isotope dilution gas chromatography-mass spectrometry (ID-GC-MS), ion chromatography (IC), UV visible spectrophotometry (UV-Vis), flow injection analysis (FIA) was used by the participants for the determination.The NIST Decision Tree was used to assign the KCRV estimate and to calculate the degrees of equivalence of each participants following the IAWG Guidance on Using NIST Decision Tree for Comparison Reporting from 30 June 2023.Successful participation in CCQM-K161 demonstrates measurement capabilities for determination of anions in seawater. Considering the IAWG Core Capability Matrix, this material falls into the matrix challenge called 'High salts content', which corresponds to the CCQM amount-of-substance category sea water, and so will support CMCs for the anions in a mass fraction range from 60 µg/kg to 25 mg/g.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 https://www.bipm.org/kcdb/.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).

Effects of Mycorrhizal and Extraradical Hyphae of Subtropical Native Tree Species on Soil Enzyme Activities and Their Stoichiometric Ratios

We aimed to study the effects of mycorrhizal and extraradical hyphae on soil physical and chemical properties and enzyme activity characteristics in a subtropical plantation and to explore its indicative effect on the effectiveness of soil nutrients. In this study, three native afforestation tree species, Cunninghamia lanceolata, Schima superba, and Liquidambar formosana, with different biological characteristics, root functional traits, and nutrient acquisition strategies in subtropical regions were selected as the research objects. Based on the method of in-growth soil cores, the nylon mesh with different pore sizes was used to limited the root system and hypha into the soil column. The soil physical and chemical properties of five kinds of hydrolase related to the carbon (C), nitrogen (N), and phosphorus (P) cycles were determined in this study. The correlation of different tree species, roots, and mycelia with soil physicochemical properties, enzyme activity, and stoichiometric ratios was analyzed. The results revealed that mycorrhizal treatment significantly affected the soil total carbon (TC) and pH but had no significant effect on hydrolase activity and its stoichiometric ratio. Tree species significantly affected soil physical and chemical properties, soil β-1,4-N-acetylglucosaminidase (NAG), β-1,4-glucosidase (βG), and cellobiohydrolase (CB) activities and soil enzyme stoichiometric ratios. The soil enzyme activity and stoichiometric ratio of the Chinese fir forest had higher values than in monoculture broad-leaved stands of both Schima superba and Liquidambar formosana. There was no significant interaction effect of mycorrhizal treatments and tree species on all soil properties, enzyme activities, and stoichiometric ratios. In addition, the soil enzyme activity and stoichiometric characteristics were mainly affected by the pH. In this study, the soil enzyme activity ratios In(BG + CB):In(AP) and In(NAG + LAP):In(AP) were lower values than the global scale, while the ratios of In(βG + CB):In(NAG + LAP) were higher than the average, indicating that the soil microorganisms in this area were limited by C and P. Moreover, the soil enzyme activity and chemical metrology characteristics were mainly affected by the pH change. In conclusion, differences in litter quality and root functional traits of tree species affected the soil enzyme activity and its stoichiometric characteristics through the shaping of the forest environment by organic matter input, and the influence of pH was the main regulating factor.

Preface

11th Brazilian Congress on Metrology (Metrologia 2021) The Metrology 2021 congress was held from October 18th to 21st, 2021. It was a remote event, with all activities done in virtual rooms. The general president of Metrology 2021 was Americo Bernardes, president of the Brazilian Society of Metrology and professor at the Federal University of Ouro Preto.Metrology 2021 Magna session was the lecture Dr. Claire M. Saundry (NIST) gave on the first day, October 18th. Dr. Saundry spoke about the main activities of the Interamerican Metrology System (or “Sistema Interamericano de Metrologia” – SIM) regarding capacity building and knowledge transfer.Following the Magna session, on the morning of October 18th, the work began with the plenary lecture given by Dr. Daniel Varela Magalhães from the Mechanical Engineering Department at USP. The speaker gave a general outline of the new edition of the International Vocabulary of Metrology (VIM).Further after, on the afternoon of October 18th, two virtual rooms were held in parallel with the sessions related to CBM (general metrology) and CBMRI (ionizing radiations). CBMRI sessions also featured four thematic discussions on specific topics of interest.The second day of the congress, October 19th, started with the lecture of Dr. Thomas Hartung from the Johns Hopkins Bloomberg School of Public Health. He spoke about assessing the health effects of drugs and chemicals, which is considered a scientific revolution and a critical application of Metrology in the Health Area. Continuing in the Health area, Dr. Cameron Miller from NIST presented his lecture on documentary standards and the development of measurement methods for UV disinfection technologies. The plenary lectures were closed by Dr. Renato Garcia from UFSC, who spoke about quality programs in medical equipment used in primary health care, specifically about post-market safety and performance trials.Later, on the afternoon of October 19th, two virtual rooms were held in parallel sessions related to CBM (general metrology) and CBMO (optical metrology).The third day of the congress started with an exciting round table about female researchers’ presence in ionizing radiations. A plenary lecture by Stephane Solve from the “Bureau International de Poids et Mesures” (BIPM) Radiometry-Photometry group followed. The main subject was an extension of the BIPM on-site primary voltage standards comparisons to AC voltages, an important topic in Electrical Metrology. Further on, the morning works ended with a round table about Metrology in Health, featuring Renata Souza from FIOCRUZ and Roberto Macoto Ichinose from the Biomedical Engineering of COPPE/UFRJ.The afternoon of the third day started with two virtual rooms that held parallel sessions related to SEMETRO (electrical metrology) and to CIMMEC (mechanical metrology). Later on, there was another round table about Metrology in Health, specifically about metrological traceability of laboratory tests, with lectures by Dr. Marcelo Medeiros from INMETRO, Debora Michele Morone D’Aiuto from FIOCRUZ, Rafael Monsores from the company CONTROLLAB and MD Luisane Maria Falci Vieira, manager of the laboratory Álvaro Apoio.The event’s last day, October 21st, started with a plenary lecture by Dr. Jim Huggett from National Measurement Laboratory (NML), talking about the role of measurement science in supporting a molecular diagnosis of SARS-COV-2, a very current and hot topic. A vivid discussion on Metrology Education followed the plenary lecture.The afternoon of the last day started with two virtual rooms that held parallel sessions related to REMEQ (chemical metrology) and CBM (general metrology). Later, round tables were held in the two parallel virtual rooms, discussing hot topics such as metrological traceability, quality control on COVID-19 diagnostics, alternative methods applied to toxicology, and a web app developed for the performance evaluation of laboratories.Metrologia 2021 disclosed about 170 articles. After the second round of revision, the editorial committee selected the best 35 to be published by IOP JPCS.Metrology 2021 had sponsors from the industrial sector (Fluke Calibration and Sartorius do Brasil (Gold sponsors) and institutional support (ARBB Consultoria em Metrologia e Qualidade, RMMG, Canal Metrologia, REDE, SBLUZ and GM Metrologia). The event’s next edition will be face-to-face in 2023, from 28th to 30th November, in Itaipava, a gorgeous area belonging to the “Imperial City” of Petrópolis, Rio de Janeiro state. You are all welcome to join us! Rio de Janeiro, RJ, Brasil, August 28th, 2023. List of Editorial committee, Organizing committee are available in this Pdf.

On the way to SI traceable primary transfer standards for amount of substance measurements in inorganic chemical analysis

During its 25 years of existence, the Inorganic Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM IAWG) has achieved much in establishing comparability of measurement results. Impressive work has been done on comparison exercises related to real-world problems in fields such as ecology, food, or health. In more recent attempts, measurements and comparisons were focused on calibration solutions which are the basis of most inorganic chemical measurements. This contribution deals with the question of how to achieve full and transparent SI traceability for the values carried by such solutions. Within this framework, the use of classical primary methods (CPMs) is compared to the use of a primary difference method (PDM). PDM is a method with a dual character, namely a metrological method with a primary character, based on the bundling of many measurement methods for individual impurities, which lead to materials with certified content of the main component. As in classical methods, where small corrections for interferences are accepted, in PDM, many small corrections are bundled. In contrast to classical methods, the PDM is universally applicable to all elements in principle. Both approaches can be used to certify the purity (expressed as mass fraction of the main element) of a high-purity material. This is where the metrological need of National Metrology Institutes (NMIs) for analytical methods meet the challenges of analytical methods. In terms of methods, glow discharge mass spectrometry (GMDS) with sufficient uncertainties for sufficiently small impurity contents is particularly noteworthy for the certification of primary transfer standards (PTS), and isotope dilution mass spectrometry (IDMS), which particularly benefits from PTS (back-spikes) with small uncertainties, is particularly noteworthy for the application. The corresponding relative uncertainty which can be achieved using the PDM is very low (< 10−4). Acting as PTS, they represent the link between the material aspect of the primary calibration solutions and the immaterial world of the International System of Units (SI). The underlying concepts are discussed, the current status of implementation is summarised, and a roadmap of the necessary future activities in inorganic analytical chemistry is sketched. It has to be noted that smaller measurement uncertainties of the purity of high-purity materials not only have a positive effect on chemical measurements, but also trigger new developments and findings in other disciplines such as thermometry or materials science.Graphical Primary Transfer Standards (PTSs) are the link between the immaterial world of the International System of Units (SI) and the material aspects of the primary calibration solutions.

Paul De Bievre down under: practical metrology in chemistry and its principles

Paul De Bievre down under: practical metrology in chemistry and its principles

Cavity optomechanical mass sensor in water with sub-femtogram resolution

Sub-femtogram resolution of an in-liquid cavity optomechanical mass sensor based on the twin-microbottle glass resonator is demonstrated. An evaluation of the frequency stability using an optomechanical phase-locked loop reveals that this cavity optomechanical sensor has the highest mass resolution of in water, which is four orders of magnitude better than that in our first-generation setup [Sci. Adv. 8, eabq2502 (2022)]. This highly sensitive mass sensor provides a free-access optomechanical probe in liquid and could thus be extended to a wide variety of in situ chemical and biological metrology applications.

Copper isotope delta measurements in high purity materials: CCQM-P213 pilot study

Main textAccurate and precise isotope ratio measurements of heavy elements are playing an increasingly important role in modern analytical sciences and have numerous applications. Today, isotope ratio measurements are typically performed with two principal techniques: thermal ionization mass spectrometry (TIMS) and multiple collector-inductively coupled plasma mass spectrometry (MC-ICP-MS). To obtain accurate results by mass spectrometry, isotopic certified reference materials (iCRMs) are needed for mass bias correction and for the validation of the method used for analysis. Thus, it is of paramount importance to achieve measurement comparability of all data reported, and to assess measurement capability of each CRM producer/National Metrology Institute (NMI). Therefore, the international comparison (CCQM-P213) was performed to assess the analytical capabilities of NMIs for the accurate determination of copper isotope ratio delta values in high purity materials. The study was proposed by the coordinating laboratories National Research Council Canada (NRC), National Institute of Standards and Technology (NIST), Bundesanstalt für Materialforschung und -prüfung (BAM) and Physikalisch-Technische Bundesanstalt (PTB) as an activity of the Isotope Ratio Working Group (IRWG) of the Consultative Committee for Amount of Substance - Metrology in Chemistry and Biology (CCQM). Participants included six NMIs and one designated institute (DI) from the six countries. Although no measurement method was prescribed by the coordinating laboratories, MC-ICP-MS with either standard-sample bracketing (SSB) or combined SSB with internal normalization (C-SSBIN) models for mass bias correction were recommended. Results obtained from the six NMIs and one DI were in good agreement.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 https://www.bipm.org/kcdb/.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).

TiN hard coating as a candidate reference material for surface metrology in chemistry: characterization and quantification by bulk and surface analyses techniques

This study presents the synthesis and characterization of TiN hard coatings as a candidate reference material for surface metrology in chemistry. TiN coatings were grown on a silicon wafer with (111) orientation using dc reactive magnetron sputtering. X-ray diffraction confirms that the diffraction phase of TiN coatings is polycrystalline, electron microscopy demonstrates that the TiN coatings presents pyramidal-shaped grains ranging from sub-micrometer to nano-size scale and with an average thickness of 666 nm. According to micro Raman results, the presence of LO phonon modes confirms that the TiN coatings are crystalline in nature and no impurities are detected. The mechanical properties at the nanoscale are evaluated using resonance tracking acoustic force atomic microscopy. The chemical composition of the TiN reveals a close 1:1 atomic ratio. The ANOVA is used to evaluate the homogeneity of the TiN via a homogeneity test according to the ISO Guide 35:2017, while, regarding the chemical composition of the Ti, the Fisher’s test demonstrates that the batch can be considered as homogeneous.

Designing an Online Course for Pharmacy Students: Case Study of Basics of Chemical Metrology

Designing an Online Course for Pharmacy Students: Case Study of Basics of Chemical Metrology

Preface

«…to progress the state of the art of chemical and biological measurement science and act as a forum for the exchange of information about measurement research, technical programs and service delivery…»Consultative Committee for Amount of Substance; Metrology in Chemistry and Biology (CCQM): Strategy Document (2021-2030)Today, more than ever, the problems of ensuring international traceability in the field of physicochemical measurements, both for science and production, and for monitoring the quality and safety of life, are relevant. The concept of “measured once, accepted everywhere” has become a cornerstone for metrologists over the world. To implement this concept, metrological institutes hold conferences, seminars, forums and other events providing participants with the opportunity to receive information about new achievements, exchange experience between laboratories and identify problems arisen in practice.List of Images, Acknowledgements, Program Committee are available in this pdf.

Development of metrological support for nucleic acid measurements

Measurements of nucleic acid have become an essential part of analytical applications in many fields including life science, medicine, veterinary medicine and biotechnology. Peculiarities of these measurements are largely determined by the uniqueness of quantity and analyte definitions. Quantitative PCR, applied for routine nucleic acids measurements, is a relative method demanding external calibrators with quantity values traceable to corresponding reference materials. Direct nucleic acid measurements became possible after introduction of the digital PCR (dPCR) method. Ensuring accurate, comparable and traceable to SI nucleic acids measurements is the focus of Nucleic Acid Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology. A number of pilot and key comparisons carried out by Working Group have shown that application of dPCR allows participating National Metrological Institutes to obtain comparable results of measurements of the sequence copy number concentrations and copy number ratios.

Metrology of cellular analysis: problems and solutions

Cellular analysis is one of the perspective developing areas of metrology. The complexity of the measuring object requires novel approaches and correct metrological support for the quantitative methods of cellular analysis. Definition of the quantitative parameters and nominal properties of the cell, standardization of methodology – these are main tasks of the Cellular Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology. The results of a number of pilot studies carried out by Working Group can be used as a first step establishing metrological traceability of the cell measurements. Development of the stable reference materials for cell quantification is a challenging problem. One of the promising solutions seems to apply synthetic cell-mimicking particles. Currently we are in the process of developing candidate synthetic reference materials for cell measurements.

Establishment of metrological traceability for fluoroquinolones measurement in monitoring plan of quality and safety for agro-product in China

Purity certified reference materials (CRMs) as the basis for traceability chains are play an important part in chemical metrology. In the context of supporting the implementation of monitoring plan of national quality and safety for agro-products, a project for development of fluoroquinolones purity CRMs was launched. These CRMs aimed to use as benchmark to assure the comparable and traceable measurement results of fluoroquinolone antibiotic residues in nationwide monitoring laboratories. In characterization, certified values were assigned by using mass balance (MB) and quantitative nuclear magnetic resonance (qNMR). Homogeneity, stability and uncertainty evaluation were sufficiently studied. These fluoroquinolones purity CRMs including enrofloxacin (GBW(E)090817), ciprofloxacin (GBW(E)090818), norfloxacin (GBW09251), fleroxacin (GBW09249), lomefloxacin hydrochloride (GBW09250), ofloxacin (GBW(E)090822), danofloxacin mesylate (GBW(E)100475), sarafloxacin hydrochloride (GBW(E)0900960), pefloxacin mesylate (GBW09256) can be used to ensure the accurate and reliable measurement results acquired in the mandatory routine monitoring by providing a metrological traceability source for establishing comparability.

Развитие мицеллярной жидкостной и тонкослойной хроматографии.

The review of the development of micellar high-performance liquid chromatography and micellar thin-layer chromatography is presented. The results of the research of the theoretical foundation and the organized solution usage as mobile phases for the analysis of plant and animal biological active substances, medicinal substances and drugs are demonstrated. The investigations had been carried out on the Chemical Metrology Department V.N. Karazin Kharkiv National University and in the State Enterprise “Ukrainian Scientific Pharmacopoeial Center for Quality of Medicines”.

The Surface Analysis Working Group at the Consultative Committee for Amount of Substance, Metrology in Chemistry and Biology: A successful initiative by Martin Seah

Dr Martin Seah, NPL, was the initiator, founder, and first chairman of the Surface Analysis Working Group (SAWG) at the Consultative Committee for Amount of Substance, Metrology in Chemistry and Biology (CCQM) at the Bureau International des Poids et Mesures (BIPM), the international organization established by the Metre Convention. This tribute letter summarizes his achievements during his chairmanship and his long‐running impact on the successful work of the group after his retirement.

Development of International Key Comparisons in the Field of Chemico-Analytical Measurements

The most challenging problems in the field of chemico- and bioanalytical measurements are described. These problems are being solved, in particular, by participating in new international comparisons organized by the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology of the International Committee of Weights and Measures (CCQM CIPM). Solutions of these challenging problems are presented. The objectives and tasks of developing key comparisons in the following areas are described: isotopic measurements; determination of the purity of substances; organic analysis; bioanalytical measurements; measurements of aerosol particle parameters; measurements in the field of gas analysis and electrochemistry. It is shown that participation in international key comparisons allows obtaining valid and reliable results of measurements of the composition and properties of gas and liquid media, as well as solid substances and materials.

Improving the accuracy of chloride measurements through participation in regular external quality assessment programme

BackgroundA chloride test is an integral part of a basic metabolic panel that is essential for the assessment of a patient’s acid-base and electrolyte status. While many methods are available commercially for the routine measurement of chloride, there is a need to address the accuracy and variability among the measurement results, especially with the prevalence of patients seeking treatment across different healthcare providers for alternative opinions. MethodA method based on sector field inductively coupled plasma isotope dilution mass spectrometry (SF-ICP-IDMS) was developed for the measurement of chloride in human serum. The SF-ICP-IDMS method was then used to assign the target values in the Health Sciences Authority (HSA) External Quality Assessment (EQA) Programme to evaluate the results of chloride test from participating clinical laboratories. ResultsThe accuracy of the measurements was evaluated by comparing the results with the certified values of Electrolytes in Frozen Human Serum Certified Reference Materials (SRM 956c and SRM 956d) from the National Institute of Standards and Technology (NIST) at different chloride concentration levels. Over a five-year period from 2014–2018, the number of clinical laboratories which participated in the EQA Programme increased from 23 to 33. Comparison of robust means from the laboratories’ results with our assigned target values revealed a reduction in relative deviation over time. The relationship between the deviation of each brand of clinical analysers and the chloride levels was established, where a larger deviation was uncovered at low chloride concentration. The SF-ICP-IDMS method was further demonstrated to be comparable with methods used by other metrology institutes in an international comparison organised by HSA under the auspice of the Consultative Committee for Amount of Substance – Metrology in Chemistry and Biology (CCQM). ConclusionThe use of metrologically traceable assigned target values enabled the study of method biasness from a small pool of dataset in each of the four brands of clinical analysers in HSA EQA Programme. This work underscores the need to improve the accuracy of chloride measurements by regular participation in an accuracy-based EQA Programme.