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 Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical MeasurementJournal Prestige (SJR): 0.316 Citation Impact (citeScore): 1Number of Followers: 30      Hybrid journal (It can contain Open Access articles) ISSN (Print) 0949-1775 - ISSN (Online) 1432-0517 Published by Springer-Verlag  [2469 journals]
• Pesticide residues in fruits and vegetables in Indonesia: findings of
five-year proficiency testing

Abstract: Abstract The first proficiency testing of pesticides in fruits and vegetables in Indonesia is reported. This report covers the findings of five-year proficiency testings. Every year, from 2016 to 2020, 18–25 laboratories join the proficiency testings and analyze 5–11 pesticides in tomato, orange, lettuce, brown rice, strawberry respectively. The number of laboratories participating in the proficiency testings tends to increase, although only 38 % of the laboratories are able to report all pesticides. More than 72 % of participants use QuEChERS or its modifications for sample preparation, all participants use gas chromatography or liquid chromatography for separation, at least 20 % of participants still rely on detectors other than mass spectrophotometer for detection, and 20 %–60 % of participants use matrix-matched calibration for quantification. The performance of laboratories is evaluated as z-score with an average of 90.8 % achieves satisfactory results while 3.3 % and 5.9 % achieve questionable and unsatisfactory results correspondingly. Overall, the performance of laboratory participants during proficiency testings is good. However, improvement is still needed, especially for the number of target pesticides for multi-residue pesticide analysis. Moreover, unsatisfactory z-scores are likely to be resulted from laboratories which use conventional solvent extraction, use detectors other than mass spectrometers, and are not accredited.
PubDate: 2022-05-10

• Comparing uncertainties—Are they really different'

Abstract: Abstract Uncertainties occur at all stages of a measurement process. Quantification of these uncertainties is important in order to make reliable decisions based on these measurement results. In some cases it can be useful to be able to compare the uncertainties associated with different measurement methods, in order to establish the method that is most reliable. A comparison can also be made between uncertainties that have themselves been evaluated using different estimation procedures. This paper discusses the comparison of uncertainties in chemical measurements using case study examples. Depending on the context, both exact and approximate F-tests are used to compare the ratios of uncertainties, while in some cases the approach is to compare separate confidence intervals.
PubDate: 2022-05-06

• Inter-comparability of analytical laboratories in quantifying polycyclic
aromatic hydrocarbons collected from industrial emission sources

Abstract: Abstract We report an inter-laboratory comparison of analytical laboratories involved in the quantification of polycyclic aromatic hydrocarbons (PAHs) collected by sampling organisations from industrial stacks (e.g. waste incinerators). Four reference solutions were prepared containing nominally 10 ng/ml, 50 ng/ml, 200 ng/ml and 500 ng/ml of naphthalene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene prior to despatch to five analytical laboratories with quantification requested in accordance with ISO 11338-2. Across four of the laboratories (the 5th returned unusable data), significant deviations from the reference concentrations were found frequently in excess of the benchmarks of 37 %—from the validation data in ISO 11338-2—and 21 %—from the Environment Agency for England’s Monitoring Certification Scheme. Also, much of the variance was systemic in nature indicating a possible issue with the quality of some of the stock solutions used by the laboratories for calibration. Whilst more proficiency testing would be welcomed to monitor and improve performance, this should be provided in addition to more support for analytical laboratories. A key mechanism of support is the standards themselves and there is a timely opportunity in that ISO/TC 146/SC 1 are due to revise ISO 11338. Possible improvements include full validation of high performance liquid chromatography and gas chromatography–mass spectrometry methods (to better understand what performance can reasonably be expected from laboratories), a requirement to correct results to individual laboratory PAH extraction efficiency, and a required uncertainty stipulated for the overall method (also aiding setting pass/fail criteria for proficiency testing).
PubDate: 2022-05-03

• Feasible stoichiometric reactions for SI traceable bromate assays

Abstract: Abstract Evaluating chemical purities by different analytical methods based on different reactions is one of the effective approaches to decrease the contribution of unknown biases that each method has, and to establish reliable reference materials. This paper describes new applications of precipitation titration with silver(I) and redox back titration with iron(II) to the assays of bromate ions which were different from a conventional titrimetric reaction with thiosulfate ions. Bromate ions are often used as a standard for redox titration as well as for evaluating water and food quality by instrumental analyses. Required measurands in these instrumental analyses are not redox properties of the ions, but the mass fraction in chemicals. Bromate ions have been determined by a conventional redox titration: iodine (triiodide) liberated by bromate ions in an acidic potassium iodide solution has been titrated with a standardized sodium thiosulfate solution. New titrimetric approaches described in the present paper directly allow to evaluate the mass fraction of the ions without iodine liberation processes in the conventional reaction, and contribute reliable analytical assays. These approaches were also attempted to the assays of iodate ions, which is one of the useful standards.
PubDate: 2022-05-02

• The path to continual improvement and business excellence: compliance to
ISO standards versus a business excellence approach

Abstract: Abstract ISO Standards provide a minimal benchmark for organisations to achieve accreditation or certification and maintain compliance to the core elements of the standard. These standards assist organisations in establishing and maintaining a quality management system. Business Excellence models are integrated collections of proven activities for how an organisation should operate to pursue excellence or world-class performance and sustainability. The focus is on the customers and internal processes to meet customer expectations. The pursuit of ISO compliance and business excellence are interrelated, synergistic and will lead to common approaches for progress and sustainability if well managed. Embracing quality assurance systems, tools of organisational excellence and benchmarking against the best international standards and practices are essential for businesses operating in a global community. The Royal College of Pathologists of Australasia Quality Assurance Programs Pty Ltd has long been a compliance-driven organisation, but more recently embraced the pursuit of business excellence by adopting the Australian Business Excellence Framework. These two approaches to quality management and continual improvement are compared and the value of incorporating both approaches is explored.
PubDate: 2022-04-30

• Provision of chemical proficiency testing round on corn-based snack food
for laboratories in the Asia-Pacific

Abstract: Abstract As the only ISO/IEC 17043:2010-accredited food PT provider in the Philippines since 2013, the Department of Science and Technology-Food and Nutrition Research Institute successfully organized a PT Round on corn-based snack food for nutrition labeling parameters. The PT Round aimed at evaluating the performance of chemical laboratories in the Asia-Pacific area on the analysis of proximates (moisture, fat, protein and ash), total dietary fiber (TDF), saturated fatty acids and minerals (iron, calcium, sodium, potassium and zinc) in corn-based snack food through an interlaboratory comparison. A sufficiently homogeneous corn-based snack food test item was distributed to 67 registered laboratories. Results were evaluated using appropriate statistical procedures based on ISO 13528:2015. The mass fractions such as moisture, fat, protein, saturated fatty acids, calcium, sodium, potassium and zinc in corn-based snack food, which have xpt with negligible uncertainties, i.e., u(xpt) ≤ 0.3σpt, were issued with z scores, while other measurands with wide variability in the results, i.e., u(xpt) > 0.3σpt, were issued with z′ scores. The xpt (in % for proximates, TDF and saturated fatty acids, and 10–5 g/g for minerals) and the percentage of laboratories that obtained “Satisfactory” performance (│z or z′ score│ ≤ 2) were: moisture (2.95, 88 %), fat (15.75, 91 %), protein (9.75, 69 %), ash (1.61, 64 %), TDF (5.04, 54 %), saturated fatty acid (5.90, 78 %), iron (2.93, 69 %), calcium (161, 74 %), sodium (139, 82 %), potassium (170, 77 %) and zinc (2.68, 85 %). This PT Round allowed to assess laboratories’ performances on the analysis of nutrition labeling parameters in corn-based snack food and improvement on performance by conducting investigative and corrective actions for those participants with “Warning” and “Action” signals.
PubDate: 2022-04-29

• Reply to “Facing a shortage of the Latin letters for the prospective new
SI symbols: alternative proposal for the new SI prefixes”

Abstract: Abstract Dominik Pražák recently published in this journal a thoughtful discussion of the implications of a shortage of Latin letters for use in the SI. This is a short reply, intended to develop the opinions in that article.
PubDate: 2022-04-27

• Is the z score sufficient to assess participants’ performance in
proficiency testing' The hidden corrective action

Abstract: Abstract Proficiency testing providers, accreditation bodies and testing laboratories should be aware that a laboratory participating in a proficiency testing round might have reported a biased result despite a satisfactory performance indicated by an assessment using uniquely the z score. A complementary performance evaluation, based on the ζ score and the assessment of the measurement uncertainty, is therefore highly recommended. This work presents an intuitive graphical tool (the Naji2 plot) that combines z and ζ scores together with the reported measurement uncertainties. This tool allows a comprehensive assessment of the laboratory performance and enables to identify the need for corrective actions. The concerned laboratory should then perform a root cause analysis and investigate their bias and/or their measurement uncertainty evaluation.
PubDate: 2022-03-18

• External quality assessment (EQA) combined with on-site technical
evaluation for capacity building in clinical microbiology laboratories in
Pakistan

Abstract: Objectives Implementation of standard laboratory practices towards accurate antimicrobial susceptibility testing (AST) is challenging in resource-constrained settings. Efforts to improve AST are required to address knowledge and practice gaps in such settings. In this study, we aimed to address these gaps through external quality assurance surveys and mentoring of laboratories in Pakistan. Methods This prospective study (May 2017–September 2019) included 10 consenting laboratories. External quality assessment (EQA) was conducted quarterly and performance scored. Each EQA cycle was followed by an on-site technical visit during which AST methodology, quality procedures and laboratory safety were evaluated using a questionnaire developed for this study. Cumulative scores of performance in the EQA and in the technical evaluation were designated “Composite Laboratory Performance Score; CLPS”. During on-site visits, feedback provided was to each participating laboratory towards addressing gaps identified. Results Over the course of the study, our data show significant improvement in CLPS amongst the laboratories included. While improvement in the CLPS scores varied between laboratories, a linear regression model showed improvement within the cohort from 21.37 (May 2017) to 91.5 (September 2019); a significant overall increase of 70.13 points (p = 0.001). Conclusion Interventions to improve AMR surveillance include quality assured reporting of antimicrobial resistance. Our data show that in resource-limited settings EQA surveys and on-site evaluations followed by guidance contribute towards such improvement. We propose that this model would be a useful tool for laboratory strengthening in such settings.
PubDate: 2022-03-01
DOI: 10.1007/s00769-022-01495-x

• Optimization of medium composition for production of a simulated urine
sample containing Enterococcus faecalis

Abstract: Abstract The production of a simulated urine sample is necessary for external quality assessment schemes in clinical testing. This study aimed to optimize the formulation of a simulated urine sample containing patient urine bacterial Enterococcus faecalis via response surface methodology based on central composite design. The results of a Plackett–Burman design experiment showed that three factors including sodium thioglycolate and peptone concentration and pH value significantly effected to concentration of E. faecalis. Notably, an initial concentration of 1.51 mg/mL of sodium thioglycolate and 3.63 mg/mL of peptone at a pH value of 8.06 of culture medium has been found to maximize the E. faecalis concentration (7.05 log (CFU/mL)). This optimal condition could be applied for production of a simulated urine sample containing E. faecalis.
PubDate: 2022-02-03
DOI: 10.1007/s00769-022-01493-z

• Improvement of reference gas calorimeter to measure the gross calorific
value of the reference methane gas having high purity (99.995 %) and
calculation of uncertainty

Abstract: Abstract Natural gas is the most widely used energy source among other gases. For this reason, measuring the gross calorific value with very high precision is of great importance for users and sellers. With the reference calorimeter designed in this study, it was aimed to obtain the calorific value “Hm” of the methane gas which is the principal component of the natural gas and has the EN ISO 6976:2016 standard. The measurements made with the designed and manufactured reference calorimeter were evaluated. The reference calorimeter can measure temperature, mass, power, amount of wastewater absorbed, type and amount of waste gas with the highest precision that TUBITAK-NMI (The Scientific and Technological Research Council of Turkey)-(National Metrology Institute) can measure. Measurements made with the designed calorimeter were insulated so that there is no heat exchange from the external environment, while the gas flow rate and temperature provided by using stable temperature sources are controlled. Certified calibration instruments were used in all measurements. The experiments were carried out at a temperature of 298.16 K. The methane gas with 99.995 % purity was used as the reference gas and as a result of the measurements; experimental data were obtained with errors ranging from 0.5 % / 0.1 %. Analyses from experimental data have shown that the greatest error in gross calorific value “(Hm)G” is due to temperature and mass measurements. The mean gross calorific value obtained using eight measurements is 55460.60 kJ kg−1 or 889.03343 kJ mol−1 within a relative expanded uncertainty of 0.2 % (k = 2).
PubDate: 2022-02-03
DOI: 10.1007/s00769-021-01486-4

• Preparation of a reference material for tea containing five pesticide
residues and its evaluation in an interlaboratory comparison study in
China

Abstract: Abstract Monitoring pesticide residues is a key item in the field of food safety. Tea matrices represent a challenge in pesticide analysis due to the high content of coextracts. An interlaboratory comparison was organized to assess the performance of 73 laboratories, from 28 regions in China, on the quantification of five pesticide residues in tea matrix reference material in order to ensure the accuracy, reliability and comparability of monitored pesticide residues in foods. The tea matrix reference material spiked with pesticides was prepared according to ISO 17034. Briefly, blank green tea was spiked with bifenthrin, permethrin, fenpropathrin, buprofezin and imidacloprid, smashed, sieved, homogenized and bottled. It was assessed to be sufficiently homogeneous and stable. Participant laboratories were requested to submit quantification results with detailed analytical protocols. Assigned values were obtained from consensus values by robust analysis, and the results were assessed using z scores. The robust standard deviations for five pesticides were lower than the expected standard deviations in our interlaboratory comparison. In total, 93.8 % (255/272) of the results were acceptable ( z ≤ 2.0) and 82.2 % (60/73) of participant laboratories had satisfactory performance in pesticide residues quantification. Analytical protocols of extraction, cleanup and quantification methods were reviewed to assess their impacts on the results. Overall, a tea matrix reference material was successfully prepared for an interlaboratory comparison, and the results indicate that most of domestic laboratories have acceptable capability in pesticides quantification, while a few of them need to further optimize their protocols to improve performance.
PubDate: 2022-02-03
DOI: 10.1007/s00769-022-01494-y

• Implementation of ISO 17034 &amp; Guide 34 in China

Abstract: Abstract This paper introduces the implementation of ISO Guide 34 and ISO 17034 in the Mainland of P R China, especially from the accreditation viewpoint. The comparisons are made regarding different aspects in accreditation, including the accreditation number, the growth (rate) as well as the findings identified during onsite assessments between reference material producers and testing laboratories. The distribution of the non-conformities is also discussed to show the impact of the changed structure from ISO Guide 34 to ISO 17034, with the presentation of highlighted typical non-conformities against ISO 17034.
PubDate: 2022-02-01
DOI: 10.1007/s00769-021-01490-8

• Trends in the development of proficiency testing for chemical analysis:
focus on food and environmental matrices

Abstract: Abstract The importance of quality in analytical chemistry stimulates the development of different tools to assure the reliability of analytical results. Among different tools, proficiency testing (PT) stands out because it can be used to evaluate bias, check uncertainty, train analysts, or certify if a laboratory can execute a method adequately and provide correct results. There is a growing demand for traceable and reliable results in analytical chemistry, which can be illustrated with the growth of ISO/IEC 17025 accreditation and the importance of PT in this context. This has led to an increase in developments and publications about PT programs. This paper reports a detailed review considering the best practices to develop PT for chemical analysis, focusing on food and environmental matrices. An evaluation of the trends and the statistical strategies in its development in the last two years was performed to guide new developments of this tool that is increasingly necessary for laboratories.
PubDate: 2022-01-29
DOI: 10.1007/s00769-021-01487-3

• Is harmonisation of performance assessment in non-quantitative proficiency
testing possible/necessary'

Abstract: Abstract The importance of laboratory performance evaluation in qualitative and interpretative proficiency testing (PT) and external quality assessments (EQA) has increased significantly over recent years. Unfortunately, the relevant ISO standards provide limited guidance on how these assessments could be harmonised. In 2014, the Eurachem PT Working Group performed an initial survey on current practices applied by PT/EQA providers in these areas. This paper presents the results of this survey along with the findings of an extensive literature review on the subject extended to 2020. Both the survey results and the literature search show that, even though a majority of scoring systems are based on simple yes/no or absence/presence responses, multiple types of performance evaluation criteria are in use for qualitative and interpretative PT/EQA schemes. This represents a clear disadvantage compared to the more aligned approach in quantitative PT/EQA schemes since laboratory proficiency between schemes is not as easily comparable. The paper presents current practices and scoring systems grouped by categories with defined criteria and may serve as a basis for further discussion and investigation towards the harmonisation of performance evaluation in qualitative and interpretative PT/EQA schemes.
PubDate: 2022-01-21
DOI: 10.1007/s00769-021-01492-6

• Assessment of homogeneity and stability of new reference material of
passion-flower fruits for proficiency testing: Pesticide residues in
purple passion fruit (Passiflora pinnatistipula)

Abstract: Abstract Passion-flowers are an important sub-group of fruits with beneficial and healthy properties. The incorporation of these fruits in the global market requires meeting safety requirements of pesticide residues in food. Assuring the absence of or low levels of pesticides in passion-flower fruits requires analytical measurements in competent laboratories. One way to demonstrate competence is to participate in proficiency testing using test items closely similar to samples routinely tested by these laboratories, with adequate homogeneity and stability. One feasible proficiency test item might be a reference material. However, currently there are a lack of reference materials of pesticides in Passiflora. This study describes the preparation of a new reference material for eight commonly used pesticides in passion-fruits to concentration levels around the maximum residue limit established by the European Union for this type of commodity. The present study aimed to assess the homogeneity and stability of the material according to ISO Guide 35. The results indicated that the material prepared was sufficiently homogeneous ( $$u_{\mathrm {hom}} < {5}\,{\%}$$ for the studied pesticides) and stable (for at least 80 days at temperatures $$\le$$ $${-20}\,^{\circ }\hbox {C}$$ ) to be used in a proficiency test of pesticides in passion-flower fruits.
PubDate: 2022-01-20
DOI: 10.1007/s00769-021-01489-1

• Meaningful expression of uncertainty in measurement

Abstract: Abstract The Guide to the expression of uncertainty in measurement (GUM) has been the enduring guide on measurement uncertainty for metrologists since its first publication in 1993. According to the GUM, a measurement should always be accompanied by a reasoned and defensible expression of uncertainty, and the primary such expression is the standard uncertainty. In this article, we distinguish between the use of an expression of uncertainty as information for the recipient of a measurement result and its use when propagating uncertainty about inputs to a measurement model in order to derive the uncertainty in a measurand. We propose a new measure of uncertainty, the characteristic uncertainty, and argue that it is more fit for these purposes than standard uncertainty. For the purpose of reporting a measurement result, we demonstrate that standard uncertainty does not have a meaningful interpretation for the recipient of a measurement result and can be infinite. These deficiencies are resolved by the characteristic uncertainty, which we therefore recommend for use in reporting. For similar reasons, we advocate the use of the median estimate as the measured value. For the purpose of propagating uncertainty in a measurement model, we propose simple propagation of the median and characteristic uncertainty and show through some examples that this characteristic uncertainty framework is simpler and at least as reliable and accurate as the propagation of estimate, standard uncertainty and effective degrees of freedom according to the GUM uncertainty framework.
PubDate: 2022-01-18
DOI: 10.1007/s00769-021-01485-5

• Assessing the performances of on-line analyzers can greatly improve free
chlorine monitoring in drinking water

Abstract: Abstract The performance of seven amperometric and one colorimetric on-line free chlorine analyzers for monitoring drinking water were assessed under both controlled and real conditions according to European standard EN 17075 “General requirements and performance test procedures for water monitoring equipment—Measuring devices” (EN 17075. Water quality—General requirements and performance test procedures for water monitoring equipment—Measuring devices. CEN Brussels, 2018). For that purpose, a laboratory test bench was developed and used to estimate under controlled conditions the metrological performances (repeatability, bias, deviation from linearity and limit of quantification) and the influence of factors such as pH and temperature. The expanded measurement uncertainties (k = 2) calculated from these performances ranged from 6 % to 38 % for amperometric sensors and colorimetric analyzer. A 7-month field trial was conducted to assess the performances under real conditions. The percentile 90 was calculated from 56 relative differences (in absolute value) between the free chlorine concentration measured by the on-line analyzer and the reference value obtained using a colorimetric method with a portable spectrophotometer. The percentiles 90 were found to be in between 10 and 19 % for all analyzers. Moreover, when looking at the continuous monitoring of free chlorine during the 7 months trial, most of the on-line analyzers showed no drift in free chlorine concentration. Control charts were also built as a tool to better monitor performances of sensors and analyzers. The control limits were fixed as the expanded measurement uncertainty of the reference method (e.g., 12 %) and the alarm limits as the expanded measurement uncertainty (k = 2) of the on-line free chlorine analyze or the maximum percentile 90 obtained under real conditions (e.g., 20 %).
PubDate: 2022-01-13
DOI: 10.1007/s00769-021-01488-2

• Facing a shortage of the Latin letters for the prospective new SI symbols:
alternative proposal for the new SI prefixes

Abstract: Abstract Recently, R. J. C. Brown analysed the needs and the possibilities to extend the current set of the SI prefixes and came up with the novel proposals of the extension of the set of the SI prefixes. This paper highlights their risks and potential side effects from the point of view the internal coherence of the SI, its future extensibility and the user adoption. Based on these, an alternative proposal is made which is free of those risks.
PubDate: 2022-01-04
DOI: 10.1007/s00769-021-01491-7

• Validation and measurement uncertainty evaluation of a GC/MS method for
the quantification of nine phthalates in tattoo and PMU inks

Abstract: Abstract A gas chromatography/mass spectrometry (GC/MS) method for the quantification of nine phthalates in tattoo and permanent make-up (PMU) ink samples was developed and validated in accordance with the criteria of ISO/IEC 17025 and international guidelines. Limit of detection (LOD) and quantification (LOQ) values were 0.02 µg g−1 –0.14 µg g−1 and 0.08 µg g−1 –0.48 µg g−1, respectively. The intermediate precision, in terms of relative standard deviations (RSD), was less than 15 % over the working range selected for all the investigated phthalates. The inter-day recoveries ranged between 76 % and 116 %. The validation study demonstrated that the method is accurate and sensitive although the development of an analytical method for this matrix is quite challenging. The relative expanded uncertainty estimated with a coverage factor (k) of 2 at a confidence interval of 95 % ranged from 7 % to 54 %. The method was applied to the analysis of 44 selected tattoo and PMU ink samples purchased on the Italian market. Phthalate content results were reported taking into account the measurement uncertainty. The uncertainty information is necessary to assess compliance of results with respect to the mass fraction limits established in the upcoming Annex XVII of Regulation (CE) N.1907/2006 (REACH).
PubDate: 2021-12-01
DOI: 10.1007/s00769-021-01480-w

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