Accreditation and Quality Assurance最新文献

The procedures used to assign values to certified reference gas mixtures and to evaluate their associated uncertainties, which are described in ISO 6143, and that were variously improved by Guenther and Possolo (Anal Bioanal Chem 399:489–500, 2011. 10.1007/s00216-010-4379-z), are further enhanced by the following developments: (i) evaluating and propagating uncertainty contributions derived from comparisons with historical reference gas mixtures of similar nominal composition; (ii) recognizing and quantifying mutual inconsistency (dark uncertainty) between primary standard gas mixtures used for calibration; (iii) employing Bayesian procedures for calibration, value assignment, and uncertainty evaluations; and (iv) employing state-of-the-art methods of meta-analysis to combine cylinder-specific measurement results. These developments are illustrated in examples of certification of two gas mixture Standard Reference Materials developed by the National Institute of Standards and Technology (NIST, USA). These examples serve only to demonstrate the methods described in this contribution and do not replace any official measurement results delivered in the certificates of any reference materials developed by NIST.

Sometimes, analytical laboratories receive requests with a small number of determinations and/or samples or outside the typical scope of analytical services. As a result, they may not have historical data on the performance of the required analytical procedures and/or appropriate reference materials. Under these conditions, it is difficult or uneconomical to use traditional quality control charts. This is the so-called start-up problem of these charts. Quesenberry’s Q charts are appropriate in these situations because they do not require a prior training phase. In the first part of this series of publications, the fundamentals and the algebraic expressions of the Q charts were presented for the individual measurements for the mean (four cases) and for the variance (two cases). This experimental study was carried out with data from quality control of mass fractions of Co in a serpentinite CRM and SiO₂ in a laterite CRM, by ICP-OES. The performance of Q charts is discussed in two situations: when the analytical process showed a clear systematic error from the beginning and when small shifts in mean and variance occurred simultaneously. In the first situation, performances of Q charts for the mean depended on the case: two of them were very sensitive even in the short run and the other two were insensitive and useless. In the second situation, the Q charts showed delayed alarms, but with a comparable behavior to the chart for individual measurements and the moving range of two. EWMA charts associated to Q charts were an excellent complement.

The present paper outlines a joint proficiency testing (PT) programme established between the Asia–Pacific Metrology Programme (APMP) and the Asia Pacific Accreditation Cooperation (APAC). This programme aims to assess the analytical performance and enhance measurement proficiencies in laboratories across various economies, with a focus on the quantification of benzoic acid in fish sauce. This PT programme was organised by the Government Laboratory, the designated institute of metrology in chemistry for Hong Kong, China (GLHK). A comprehensive invitation extended to both APMP and non-APAC members resulted in the participation of 41 laboratories from 19 different economies. The metrological reference value for benzoic acid, provided by GLHK, was determined utilizing isotope-dilution mass spectroscopy (IDMS) with traceability to the International System of Units (SI). This SI-traceable reference value enhances the quality of participants’ measurements and promotes the awareness of traceability among the participants, enabling a more accurate evaluation of their results. Concurrently, this approach facilitates the building of measurement capabilities among participants, fostering more robust connections between metrology institutes and testing laboratories. The programme also revealed a notable deficiency in the understanding of statistical concepts among some participants, including the coverage factor, degrees of freedom, standard uncertainty, and expanded uncertainty. Proper interpretation of zeta-scores or E_n scores based on measurement uncertainties, when analysed alongside z-scores, proves to be indispensable for an accurate assessment of the participants’ measurement competencies and their ability to evaluate measurement uncertainty. The assessment of participants’ performances, taking into account measurement uncertainties, serves as a benchmark for participants to gauge the validity of their measurement uncertainty evaluations.

Purity-evaluated inorganic materials, which are potential primary reference materials (PRMs) in chemistry, are crucial to the production of inorganic calibration solutions with metrological traceability to the International System of Units (SI). Purity evaluation is typically performed by individually assaying all possible impurities (gaseous and nongaseous) in a material, but technical challenges and the lack of resources are creating bottlenecks in developing effective purity assay procedures. This study describes a nongaseous impurity assay procedure developed and used at Korea Research Institute of Standards and Science (KRISS) to evaluate the purities of inorganic PRMs. Inductively coupled plasma mass spectrometry (ICP-MS) is used to assay more than 60 impurity elements in a single day, and external glow discharge mass spectrometry (GDMS) data are used to complement ICP-MS data. All aspects of the impurity assay procedure, including sample preparation, instrument operation, and data treatment, are described in detail. It is shown that the procedure is applicable to high-purity Al, As, Cu, NaCl, Se, Si, and Zn, and that a target relative uncertainty of 0.005 % for purity values can be satisfied even if individual impurity data are quite uncertain. Particular emphasis is on clearly specifying the measurand and target uncertainty for developing a fit-for-purpose assay procedure, as they determine the acceptable level of assay quality and help preventing misinterpretation of assay results.

Clause 6.5 of the ISO/IEC 17025:2017 standard describes the requirements for the metrological traceability of measurement results of a testing or calibration laboratory. Subclause 6.5.2 describes three ways to establish traceability to the International System of Units (SI). However, it is not technically possible to trace the bacterial strains used in a microbiology laboratory to the SI unit. So, when selecting a bacterial strain in a microbiology laboratory for quality assurance purposes, the laboratory needs to fulfill the subclause 6.5.3 (a) of the ISO/IEC 17025:2017 standard i.e., the laboratory needs to utilize a certified bacterial strain provided by a competent producer. So, when procuring a bacterial strain to fulfill this subclause, we need to ensure two points; (a) the bacterial strain is certified and (b) the producer is competent. A certified bacterial strain produces well-defined biochemical reactions and possesses a defined genomic sequence. There are various well-known certified bacterial strains, such as American Type Culture Collection (ATCC) strains, National Collection of Type Cultures (NCTC) strains etc. The laboratory also needs to make sure that the producer of these certified bacterial strains is competent, i.e. ISO 17034 accredited. Only when these two conditions are met, a microbiology laboratory can safely assume that it meets the requirements of subclause 6.5.3 (a) of the ISO/IEC 17025:2017 standard. For a particular bacterial species, from the vast number of strains available, the laboratory also needs to consider which specific strain to procure. The purpose of this article is to discuss why a testing microbiology laboratory needs bacterial reference materials and how it should select a bacterial reference material for quality assurance purposes from the ISO/IEC 17025:2017 standard point of view.

Accurately determining the calorific value of aviation kerosene is crucial for optimizing aircraft engine efficiency and design testing. However, current measurement methods exhibit significant uncertainties, necessitating an assessment of the uncertainty associated with measuring the calorific value of aviation kerosene to establish precise results. The present paper introduces the oxygen bomb calorific value measurement method and the probability box model, proposing an improved aviation kerosene calorific value uncertainty evaluation method by combining it with the MCM method. An uncertainty evaluation model based on GUM method, MCM method, and improved MCM method is established in conjunction with experimental data. The analysis of different models demonstrates that the improved MCM method effectively considers the uncertainty of corresponding distribution parameters of variables based on their own uncertainties, providing a reliable approach for calculating the heating value uncertainty of aviation kerosene.

Lead exposure is a well-known health concern, affecting children worldwide. We aim to assess children’s blood lead levels (BLLs), and the association of risk factors with elevated BLL in children since the phase-out of leaded gasoline. We enrolled 8085 outpatient children to assess their blood lead levels, and the associations with social-demographic factors. Social-demographic information was obtained by using questionnaires. Multivariable linear and logistic regression models were performed to explore the associations between social-demographic factors and elevated BLLs. The geometric mean BLL was 15.96 μg/L. The prevalence rates of elevated BLLs (≧ 100 μg/L and ≧ 50 μg/L) were 2.0 % and 10.9 %, respectively. BLLs in boys were higher than that in girls (P < 0.001). Girls had a lower risk of BLLs above 50 μg/L than boys (OR = 0.83, 95 % CI 0.71–0.96). Father’s occupation as a skilled laborer or professional worker and living in the suburbs significantly contributed to the elevated BLLs ( ≧ 50 μg/L), with the ORs of 1.39 (1.06–1.81), 1.33 (1.01–1.75) and 1.24 (1.02–1.50), respectively. Our results suggested that children who lived in suburbs and whose fathers were skilled laborers and professional workers were more likely to have BLLs above 50 μg/L.

The purpose of this study was to develop a rapid, sensitive, and precise RP-HPLC (Reverse-Phase High-Performance Liquid Chromatography) method for the estimation of asiaticoside (AC) using the analytical quality by design (AQbD) approach. Initially, important AQbD prerequisites like analytical target profile (ATP) and critical analytical attributes (CAAs), such as theoretical plates and tailing factor, were defined. The final chromatographic conditions for the analysis of AC consist of stationary phase {A COSMOSIL 5C18-MS-II packed column (250 mm × 4.6 mm i.d, 5 µm)}, mobile phase was S_mix {Methanol and Acetonitrile (40:25)}, and Orthophosphoric acid buffer (0.025 % OPA) in the ratio of 65:35 v/v at a flow rate of 1.0 mL/min and detection wavelength was 205 nm. The diversity in CAAs with different inputs was explained using the Ishikawa fishbone diagram. Taguchi design was selected as the first screening design to choose the critical material attributes (CMAs) that influence the method development. Subsequently, for more systematic optimization of the chromatographic technique and evaluation of CAAs, central composite design (CCD) was employed. In conclusion, the findings of the present study validated the utility of AQbD in the systemic design of a liquid chromatographic method with fine sensitivity for AC estimation in pharmaceutical products.

From 2008 to 2020, the Ministry of Food and Drug Safety (MFDS) and the Korea Research Institute of Standards and Science (KRISS) jointly conducted a proficiency testing (PT) program for the analysis of pesticide residues in kimchi cabbage and ginseng powder. This collaborative effort marked a significant milestone in South Korea, being the first instance of employing metrologically traceable assigned values, determined via isotope dilution mass spectrometry (IDMS), in PT programs. The focus was on a selective range of pesticides, including diazinon, chlorpyrifos, p,p’-DDE, γ-HCH (lindane), α-endosulfan, and β-endosulfan. Each biennial PT program centered on two of these pesticides with participating laboratories reporting their mass fractions in provided samples. PT samples were prepared meticulously prepared in powder form by KRISS, ensuring homogeneity and stability, integral for the accuracy of the testing. The paper elaborates on the intricate processes involved in PT sample preparation and the rigorous assignment of values. To evaluate laboratory proficiency, the Horwitz equation was utilized as a general mode to set for standard deviations in proficiency assessment. An in-depth review of seven PT programs conducted over this period demonstrates the significant role these programs played in advancing the measurement competencies of laboratories, underscoring the novelty and impact of this long-term collaborative effort.