Accreditation and Quality Assurance最新文献

Based on ISO 17034 and ISO Guide 35, a new series of matrix reference materials for 23 trace elements in 2 mg/mL gold solutions with five concentration levels (0, 1, 5, 10 and 20) ng/mL were developed, respectively. High-purity gold CRM GBW02793 with purity of 99.9995 % used as raw material was dissolved and then doped with multi-element solutions to prepare the candidate RMs. For ICP-MS measurements, matrix-matched and internal standard calibrations were studied and evaluated. The limits of detection (LoDs) ranged from 0.002 to 0.35 ng/mL. The satisfactory spike recoveries from 96 % to 108 % were obtained, demonstrating the measurement trueness. The ICP-MS method was also applied in the homogeneity and stability study. The statistical analysis suggested that the elements were well distributed by measuring 11 units with duplicate analysis for each. Besides, no significant trends were observed in the long-term stability test at room temperature for 12 months or in the short-term stability test at 60 ℃ and − 20 ℃ for 7 days. Through collaborative characterization by eight expert laboratories, the RM at each concentration level was certified for the mass fractions of 23 elements, respectively. All applied measurement methods in the characterization were further validated by using CRM ERM-EB507. The measurement results from all laboratories showed great consistency, and the overall mean values which were consistent with the target values were used as the certified values. Additionally, uncertainties arising from inhomogeneity (u_bb), instability (u_s) and value assignment (u_char) were comprehensively combined. The developed RMs would ensure reliable and traceable analytical results of trace elements in fine gold and gold jewelry.

In many analytical measurements, the analyte concentration in test samples can vary considerably. In such cases, the standard deviation (SD) quantifying measurement imprecision should be expressed as a function of the concentration, c: ({s}_{c}=sqrt{{mathrm{s}}_{0}^{2}+{ s}_{r}^{2}{c}^{2}}), where s₀ represents a non-zero SD at zero concentration and s_r represents a near-constant relative SD at very high concentrations. In the case of SD repeatability, these parameters can be estimated from the differences of duplicated results measured on routine test samples. Datasets with a high number of duplicate results can be obtained within internal quality control. Most procedures recommended for this estimation are based on statistically demanding weighted regression.

This article proposes a statistically less demanding procedure. The s₀ and s_r parameters are estimated from selected subsets of absolute and relative differences of duplicates measured at low to medium concentrations and high to medium concentrations, respectively. The estimates are obtained by iterative calculations from the root mean square of the differences with a correction for the influence of the second parameter. This procedure was verified on Monte Carlo simulated datasets. The variability of the parameter estimates obtained by this proposed procedure may be similar or slightly worse than that of the estimates obtained by the best regression procedure, but better than the variability of the estimates obtained by other tested regression procedures. However, a selection of the duplicates from an inappropriate concentration range may cause a substantial increase in variability of the estimates obtained.

Direct monitoring of volatile organic compounds emitted from industrial sources as well as the monitoring of ambient levels thereof in the atmosphere play an important role in providing data for various legislative requirements. There are many volatile organic compounds emitted to the atmosphere, from biomass burning, power stations, and many other sources. Primary reference gas mixtures of volatile organic compounds containing six components, namely benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (BTEX) were prepared by gravimetric methods at nominal amount of substance fractions of 10 µmol/mol. The preparation was performed using the stainless steel (loop) method and direct liquid injection method using gas tight syringe connected to a dedicated syringe heater for comparison purposes. The results of the gravimetric values for both methods were within 1 % of the nominal amount of substance fraction. After the preparation, comparison was achieved by analysis of the BTEX gas mixtures using gas chromatography with flame ionisation detection (GC-FID) and showed comparability to within 2 % of the gravimetric values. The contributions to the uncertainty of measurement were from weighing stainless steel tubes, syringes, and gas cylinders, as well as purity data. The contribution to the uncertainty of measurement from the analysis by GC-FID were repeatability and reproducibility. The combined expanded uncertainty of measurement was between 1.09 % and 3.51 %. The larger deviation from the gravimetric values and associated uncertainty was observed for benzene due to its higher volatility compared to the other components. The BTEX reference gas mixtures prepared in this study are currently being used as a source of traceability in South Africa for air pollution monitoring purposes.

The analysis of bromate is of particular interest for the assessment of water and food quality due to its toxicity. Analytical instruments such as ion chromatography have been used to measure bromate and require standard solutions for instrument calibration. A measurement method for potassium bromate as the source material of the standard solution has already been established. This paper describes the certification and long-term stability monitoring of bromate ion standard solutions with comprehensive uncertainty evaluations. The stability of potassium iodate is also presented as additional information.

Most of the papers that treat the composition of essential oils for this purpose use GC/MS or GC/MS and GC/FID techniques for the identification and/or quantification of individual compounds. Therewithal, papers usually treat the composition as semiquantitative (percentage composition as the area of the peak of a particular compound in relation to the total area of ​​the peaks on the chromatogram, given as 100 %). At the same time, the quality of the results is not treated in metrological terms. A GC/MS method for the quantification of components present Helichrysum italicum hydro-distilled essential oil samples from Bosnia and Herzegovina with a similar composition was developed and optimized. The stability of the method setup and adequacy of sample storage and manipulation were assessed. Calibration method and assessment of measurement uncertainty were established for neryl acetate, one of the major compounds with known health benefits.

In this study, analytical method validation has been done for the measurement of carbon dioxide/nitrogen (CO₂/N₂) and methane/nitrogen (CH₄/N₂) calibration gas mixtures using gas chromatography with flame ionization detector (GC-FID). Class-I calibration gas mixtures (CGMs) of CO₂ (500 µmol mol⁻¹ to 1100 µmol mol⁻¹) and CH₄ (2 µmol mol⁻¹ to 130 µmol mol⁻¹) used in method validation process has been prepared gravimetrically following ISO 6142-1. All prepared gas mixtures have expanded uncertainty 1 % at coverage factor (k) of 2 with 95 % confidence. The following parameters are chosen for this case study which include selectivity, accuracy, precision, linearity, limit of detection (LOD), limit of quantification (LOQ), robustness, stability, and uncertainty. Different statistical approaches are taken into consideration for each parameter assessment. The results indicate that GC-FID is selective for CO₂ and CH₄. CGMs represent good repeatability and reproducibility having percentage relative deviation < 1 % among measurements. A good linear behaviour was observed for CGMs of CH₄ and CO₂ on basis of least square regression with R² value 0.9995 and 1, respectively. LOD and LOQ for CH₄ are calculated 0.47 and 1.59 µmol mol⁻¹ based on signal-to-noise ratio by taking its lowest concentration of 2.9 µmol mol⁻¹. The in-house validated method for GC-FID using CGMs for the measurement of greenhouse gases (CO₂ and CH₄) is found to be precise, accurate and fit for purpose.

Nuclear magnetic resonance (NMR) has fast emerged as a quantitative platform for it offered numerous advantages over chromatographic methods in analyzing purity and determining content of organic compounds. However, the mechanism of parameter settings has not been further investigated causing the improper or incorrect use in the widespread qNMR applications. This study aims to construct a quantitative ¹H NMR methodology based on the experiment optimization and simulation and explain the impact of parameter settings on accuracy. We successfully applied the proposed ¹H qNMR method with the internal standard method to assess the purity of ofloxacin, a commonly used antibacterial drug. The study showed that parameter settings, including flip angle, relaxation delay, transmitter frequency offset, scan number and data point, had different effects on the quantification errors (0.5 % to 8.9 %). The method validation proved that the ¹H qNMR methodology delivered high accuracy with the measurement uncertainty (0.60 %). The results demonstrated that the proposed ¹H qNMR method provided clear guidance on the practical implementation of accurate quantification of low molecular mass compounds (< 500 g/mol).

To analyze and statistically compare common errors in the evaluation of measurement uncertainty in medicine and health field, using literature research and comparison with national standards, in order to understand the current status of measurement uncertainty evaluation in the medicine and health field. Using Chinese National Knowledge Infrastructure (CNKI) as the sample population, Stratified Proportional Sampling (PPS) was used to extract journal articles related to measurement uncertainty in the field of medicine and health. The articles were compared with the Eurachem/CITAC Guide QUAM to analyze measurement uncertainty errors. Academic attention to measurement uncertainty in the field of medicine and health in the CNKI literature database has shown explosive growth since 2005. Seven common errors in measurement uncertainty evaluation were identified. None of the 30 journal articles analyzed were error-free, with a total error rate of 44 %. The error rate for ignorance of blank uncertainty was 87 %, improper evaluation of standard curve was 67 %, improper significant figures were 60 %, and insufficient information for Type B evaluation was 50 %. The error rate for provincial and higher-level institutions was 48 %, while the error rate for institutions below the provincial level was 43 %. The difference between the two error rates was not statistically significant (p = 0.523). There is an urgent need to improve the rationality of measurement uncertainty evaluation in medicine and health field, and to strengthen the education and academic communication through national and international cooperation.

Graphical abstract

The biotechnology policy encourages the creation of networks of institutions that carry out bioassays and preclinical studies and stimulate the implementation of principles of good laboratory practice (GLP). However, it becomes essential for trained and qualified professionals to understand, develop procedures and documents, and properly implement quality management requirements to implement a laboratory quality system. The use of tools such as multicriteria decision aid (MCDA) can assist in managing and implementing the quality system in institutions and laboratories. This research aimed to demonstrate the perception of the degree of difficulty in understanding GLP principles perceived by the respondents and analyzed through the MCDA model. According to the MCDA method, a survey was carried out with 27 professionals from laboratories who answered a questionnaire with a numerical scale of very difficult, difficult, regular, neutral, and easy for each GLP requirement. Results evidenced the GLP criteria that require a smaller and greater effort to be understood and allowed the identification of efforts level to increase each GLP criteria's level of understanding. The MCDA confirms to be a robust tool to identify and validate the participants' perception of GLP criteria, considering the diversity of professionals and their different qualifications, enabling the construction of training content that considers the difficulty levels of each criterion. This strategy helps in the management of the laboratory and the dissemination of knowledge of GLP principles to biotechnology professionals, academics, and students.