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  Subjects -> CHEMISTRY (Total: 909 journals)
    - ANALYTICAL CHEMISTRY (56 journals)
    - CHEMISTRY (643 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (43 journals)
    - ORGANIC CHEMISTRY (47 journals)
    - PHYSICAL CHEMISTRY (71 journals)

CHEMISTRY (643 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 14)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 31)
ACS Catalysis     Hybrid Journal   (Followers: 53)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 23)
ACS Combinatorial Science     Hybrid Journal   (Followers: 23)
ACS Macro Letters     Hybrid Journal   (Followers: 28)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 44)
ACS Nano     Hybrid Journal   (Followers: 328)
ACS Photonics     Hybrid Journal   (Followers: 15)
ACS Symposium Series     Full-text available via subscription  
ACS Synthetic Biology     Hybrid Journal   (Followers: 25)
Acta Chemica Iasi     Open Access   (Followers: 6)
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 8)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 7)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 8)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 9)
Adsorption Science & Technology     Open Access   (Followers: 7)
Advanced Functional Materials     Hybrid Journal   (Followers: 62)
Advanced Science Focus     Free   (Followers: 5)
Advances in Chemical Engineering and Science     Open Access   (Followers: 77)
Advances in Chemical Science     Open Access   (Followers: 21)
Advances in Chemistry     Open Access   (Followers: 27)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Environmental Chemistry     Open Access   (Followers: 7)
Advances in Enzyme Research     Open Access   (Followers: 11)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 12)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 27)
Advances in Nanoparticles     Open Access   (Followers: 17)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Polymer Science     Hybrid Journal   (Followers: 45)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 4)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 8)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alchemy : Journal of Chemistry     Open Access   (Followers: 3)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 69)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 22)
American Journal of Chemistry     Open Access   (Followers: 34)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Hybrid Journal   (Followers: 15)
Anadolu University Journal of Science and Technology A : Applied Sciences and Engineering     Open Access  
Analyst     Full-text available via subscription   (Followers: 37)
Angewandte Chemie     Hybrid Journal   (Followers: 186)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 274)
Annales Universitatis Mariae Curie-Sklodowska, sectio AA – Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 4)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 9)
Applied Spectroscopy     Full-text available via subscription   (Followers: 26)
Applied Surface Science     Hybrid Journal   (Followers: 34)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 3)
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access  
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 4)
Avances en Quimica     Open Access  
Biochemical Pharmacology     Hybrid Journal   (Followers: 11)
Biochemistry     Hybrid Journal   (Followers: 382)
Biochemistry Insights     Open Access   (Followers: 7)
Biochemistry Research International     Open Access   (Followers: 7)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 11)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 2)
Biomacromolecules     Hybrid Journal   (Followers: 24)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 142)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 93)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 20)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 25)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 7)
Carbohydrate Research     Hybrid Journal   (Followers: 25)
Carbon     Hybrid Journal   (Followers: 70)
Catalysis for Sustainable Energy     Open Access   (Followers: 10)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 10)
Catalysis Science and Technology     Hybrid Journal   (Followers: 10)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 14)
Cellulose     Hybrid Journal   (Followers: 13)
Cereal Chemistry     Full-text available via subscription   (Followers: 5)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 2)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 23)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 75)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 28)
Chemical Physics Letters : X     Open Access  
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 22)
Chemical Reviews     Hybrid Journal   (Followers: 219)
Chemical Science     Open Access   (Followers: 29)
Chemical Technology     Open Access   (Followers: 36)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 57)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 21)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry     Open Access  
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 33)
Chemistry & Industry     Full-text available via subscription   (Followers: 9)
Chemistry - A European Journal     Hybrid Journal   (Followers: 184)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 16)
Chemistry and Materials Research     Open Access   (Followers: 21)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Open Access   (Followers: 3)
Chemistry Letters     Full-text available via subscription   (Followers: 46)
Chemistry of Materials     Hybrid Journal   (Followers: 281)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Full-text available via subscription   (Followers: 21)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 1)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 12)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 11)
Chromatographia     Hybrid Journal   (Followers: 22)
Chromatography     Open Access   (Followers: 3)
Chromatography Research International     Open Access   (Followers: 5)
Cogent Chemistry     Open Access   (Followers: 2)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 11)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 23)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Communications Chemistry     Open Access   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 7)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 1)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 13)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 4)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 7)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 8)
Croatica Chemica Acta     Open Access  
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Chromatography     Hybrid Journal  
Current Green Chemistry     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 6)
Current Microwave Chemistry     Hybrid Journal  
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 14)
Current Research in Chemistry     Open Access   (Followers: 9)
Current Science     Open Access   (Followers: 77)
Current Topics in Medicinal Chemistry     Hybrid Journal   (Followers: 9)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 2)
Dalton Transactions     Full-text available via subscription   (Followers: 26)

        1 2 3 4 | Last

Similar Journals
Journal Cover
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement
Journal Prestige (SJR): 0.316
Citation Impact (citeScore): 1
Number of Followers: 31  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0949-1775 - ISSN (Online) 1432-0517
Published by Springer-Verlag Homepage  [2351 journals]
  • Fifteenth International Symposium on Biological and Environmental
           Reference Materials (BERM-15)
    • PubDate: 2019-06-01
       
  • Determination and quality evaluation of Zhilou lotion by quantitative
           analysis of multicomponent with a single marker
    • Abstract: To develop a quantitative analysis of multicomponent by single-marker method for the simultaneous determination of fourteen components in Zhilou lotion, emodin was selected as an internal reference, and the relative correction factors of gallic acid, caffeic acid, polydatin, hyperoside, isoquercitrin, quercitrin, homoplantaginin, resveratrol, hispidulin, aloe emodin, rhein, chrysophanol and emodin methyl ether were established. The accuracy of quantitative analysis of multicomponent by single-marker method was verified by comparing the contents of the fourteen components calculated by the external standard method with those of the quantitative analysis of multicomponent by single-marker method. In a certain linear range, the correction factor of gallic acid, caffeic acid, polydatin, hyperoside, isoquercitrin, quercitrin, homoplantaginin, resveratrol, hispidulin, aloe emodin, rhein, chrysophanol and emodin methyl ether relative to emodin is good. The contents of the 14 components in 10 batches Zhilou lotion were measured. No significant difference was found in the quantitative results between the established quantitative analysis of multicomponent by single-marker method and external standard method. The established quantitative analysis of multicomponent by single-marker method could act as an accurate and convenient method to determine the 14 components in Zhilou lotion and could be used to control the quality of Zhilou lotion.
      PubDate: 2019-06-01
       
  • Optimization of peak area precision of a GC–MS drug screening method
           using a nonparametric sign test
    • Abstract: The optimization of a number of gas chromatography–mass spectrometry (GC–MS) parameters in order to improve peak area precision through the application of a nonparametric statistical test (the sign test) is demonstrated. As an example, the drug screening method used at the Swedish National Forensic Centre (NFC) is optimized, but in principle, any GC–MS method could be optimized using this approach. The GC–MS parameters investigated were those often overlooked in the optimization process, namely injection volume, liner type, oven temperature program, final oven temperature, MS scan range and MS scan rate. The influence of these parameters on the precision of the peak area responses of 11 different compounds in a test mixture was evaluated using the sign test for pairwise comparison. This nonparametric test provides probability values which facilitate the ranking of parameters according to their influence on peak area variation as well as providing a measure of their statistical significance. This study presents the resulting optimized method and shows that the decreased total variation depended predominantly on liner type and MS scan rate settings. This work also shows that optimization of analytical methods can be achieved using simple and easily accessible statistical tools.
      PubDate: 2019-06-01
       
  • Data integrity: requirements set in the accreditation standards
    • Abstract: The requirements for the competence of laboratories are described in two standards, namely ISO/IEC 17025 and ISO 15189. The former applies to all laboratories except medical laboratories where the latter is the most appropriate. The requirements of both standards include specific references to data and other related terms, their protection and integrity. The recently revised ISO/IEC 17025 introduces additional provisions for the control of data and information management compared to those of the 2005 edition. Both standards include provisions for the use of laboratory information management system(s) for the collection, processing, recording, reporting, storage or retrieval of data. ISO 15189 addresses these issues in more detail in order to meet the particular needs of the sector dealing with personal data of the patients. This article presents the requirements for data integrity and the control of relevant components of the management system set by the standards for laboratories as well as for some other conformity assessment bodies of importance for laboratory work, namely reference materials producers (ISO 17034) and proficiency testing providers (ISO/IEC 17043). Some additional regulatory requirements recently implemented are also discussed.
      PubDate: 2019-06-01
       
  • Development of a certified reference material for lead in noodles powder
    • Abstract: Food Safety and Standards Authority of India has set maximum permissible level of lead in noodle at 2.5 mg/kg. The standardized lead measurement is of high priority in food matrix to obtain closer comparability of results obtained using routine measurement procedures. For this purpose, certified reference material (CRM) for lead in noodle matrix is required to assess analytical methods performance with respect to their validation, calibration and of comparability of measurements between laboratories. Considering the unavailability of matrix-matched reference materials, National Centre for Compositional Characterization of Materials (BARC-NCCCM) has initiated a program for the production of a noodle CRM for the certification of lead mass fraction. Various parameters for homogeneous spiking were optimized for the production of 2.35 kg of homogeneous noodle matrix. Parameters for sample digestion and minimum sample intake for analytical homogeneity (HE) were established before carrying out the homogeneity test between and within bottles. Homogeneity assessment and stability tests were carried out according to the ISO Guide 34 and 35. The certified value was assigned after inter-laboratory comparison exercise where eight national laboratories of repute from both government and private sector participated.
      PubDate: 2019-06-01
       
  • Verification of nitrous oxide primary standard gas mixtures by gas
           chromatography and cavity ring-down spectroscopy for ambient measurements
           in South Africa
    • Abstract: Nitrous oxide (N2O) is an important greenhouse gas and is the third-largest contributor to global warming with a global warming potential (GWP) higher than that of carbon dioxide. Ambient N2O is monitored globally and described at nanomole per mole (nmol mol−1) levels. Metrologically traceable and highly accurate N2O gas standards are required to understand the behaviour of the greenhouse gases in the atmosphere and GWP. A group of primary standard gas mixtures (PSGMs) in aluminium cylinder material has been prepared in synthetic air for the calibration of analytical instruments for measurement of N2O at an ambient level. An automatic weighing system with a mass comparator and a fully automated circular rotary plate, as well as a gas filling station, was used in the preparation of the gas mixtures. Analytical methods such as gas chromatography coupled with micro-electron capture detector and cavity ring-down spectroscopy were adopted in the verification process. Four PSGMs in the final preparation step were used to analyse unknown background and filtered air samples at the ambient level. An expanded uncertainty relative to the gravimetric amount fraction was found to be 0.02 %. Results show that the background air samples lie within the calibration range with 329 to 330 nmol mol−1 obtained and 135 nmol mol−1 obtained for filtered air sample.
      PubDate: 2019-06-01
       
  • Development of a usability scale based on the three ISO 9241-11 categories
           “effectiveness,” “efficacy” and “satisfaction”: a technical
           note
    • Abstract: An emerging intervention in the area of dementia therapy is serious gaming. Serious gaming is understood as any meaningful use of computerized game whose chief mission is not entertainment. Given the abundance of available serious games for people with dementia, it seems desirable to appraise and compare their respective user-friendliness in a standardized way. To close the research gap of missing standardized instruments, this article outlines an approach to establish a valid and reliable scale for observer-rated usability assessments, rooted in the International Organization for Standardization (ISO) standard 9241-11 with its categories: effectiveness, efficiency and satisfaction. Three steps were undertaken to develop the scale: (1) search for usability-related terms in the literature, (2) ranking of expressions according to ISO 9241-11 and (3) statistical analysis including across-rater means, selectivity scores, principal component analysis (PCA), discriminant function analysis (DFA) and inter-rater reliability (Cronbach’s alpha). In total, 105 expressions were found. PCA yielded a single factor. DFA yielded Wilk’s Lambda of 0.243, which was statistically significant. For each category, five expressions were determined which represent that category best, being the ones with highest mean in that category and, in case of ties, expressions with highest selectivity. Cronbach’s alpha of those items was 0.435. However, even those items do not discriminate well between categories, since inter-rater reliability is inacceptable. Therefore, it is recommended to administer this scale only to assess usability as a global concept and not to discriminate between the three ISO categories. It might be worthwhile for ISO to review standard 9241-11.
      PubDate: 2019-06-01
       
  • Congresses, conferences, workshops and courses
    • PubDate: 2019-05-09
       
  • Report on the 41st meeting of ISO/REMCO
    • Abstract: The 41st meeting of the Reference Material Committee of ISO, ISO/REMCO, was held in Ottawa, Canada, from 10 to 13 July 2018 and was hosted by the National Research Council of Canada. This report details and summarises the two brainstorming sessions that was held as part of the meeting, as well as the discussions and findings of the associated group sessions and meetings. Emphasis is placed on the two new guidance documents that the committee is drafting.
      PubDate: 2019-05-06
       
  • Improving laboratory economic and environmental performance by the
           implementation of an environmental management system
    • Abstract: The RCPAQAP is a medium-sized healthcare organisation with a laboratory, logistics and office area. The organisation begun integrating an environmental management system as well as Lean and Business Excellence into its business practice. There have been real and tangible benefits to the organisation in terms of environmental footprint, cultural change and financial performance. There have been significant savings in waste, power and reduced paper usage. The total savings over 3 years were of the order of $800000. There has also been cultural change among the staff. The organisation has achieved accreditation to ISO 14001 and received an award from the Australian Business Excellence Awards scheme. The RCPAQAP has been able to document a process that has led to the successful integration of an EMS into business practice and has recorded real benefits from the exercise.
      PubDate: 2019-05-06
       
  • Verifying and assigning own target values and ranges for internal quality
           control
    • Abstract: There is considerable variation in laboratory practices with regard to the review of internal quality control (IQC), and the literature is not exhaustive on the subject of own control limits, its interpretation, when to switch it over, and its benefits for routine practice and even for patient monitoring. The purpose of the present article is to stress the routine interpretation and challenges related to own results for IQC management. The first 20 (initial) measures, as well as monthly and cumulative IQC results of immunochemical tests, were analyzed for the selected tumor markers and hormones. While the average tended to get closer to the manufacturer value by increasing the number of measurements, the analytical coefficient of variation (CVA) tended to increase. Most parameters showed significant differences between initial and cumulative CVA, which were lower than the manufacturer’s specifications. While the quality specifications based on biological variation best fit the analytical and clinical purpose of our laboratory tests, we must be aware that the manufacturer’s control range, and even the method specification, should be used carefully, because it is usually wider than our goals.
      PubDate: 2019-04-24
       
  • Fifteen years of proficiency testing of total petrol hydrocarbon
           determination in soil: a story of success
    • Abstract: The total petrol hydrocarbon (TPH) content in soil is determined by gas chromatographic separation and flame ionisation detection according to ISO 16703 in routine laboratories for about 20 years. The development of the interlaboratory variability observed with this analytical procedure over 15 years in a proficiency testing scheme conducted annually with more than 170 participants is evaluated in detail. A significant improvement of the reproducibility standard deviation among participants is observed over the years and attributed to an increasing familiarity with the procedure. Nevertheless, the determination of TPH in the environmentally relevant mass fraction range between 500 mg/kg and 10 000 mg/kg in soils or sediments is far from reaching the reproducibility standard deviations predicted by the Horwitz curve. It is seen that laboratories with sporadic participation tend to report higher bias, while a core group of laboratories participating on a regular basis arrived at reproducibility standard deviations below 20 %. Results from a given laboratory obtained on two different samples tend to be highly correlated in the same PT round indicating a sound repeatability. Expectedly, the within-laboratory correlation between results from consecutive rounds was considerably lower. However, results from consecutive rounds with a temporal distance of 1, 2 or 3 years revealed largely similar correlations which suggests that the within-laboratory reproducibility adjusts to a constant level at least after a period of 1 year.
      PubDate: 2019-04-24
       
  • Valid machine learning algorithms for multiparameter methods
    • Abstract: In the light of recent food fraud cases, the issue of food authenticity is receiving increasing attention. New analytical methods and evaluation approaches are currently being proposed. In this framework, the evaluation of mass spectral profiles constitutes a promising avenue, e.g. for the determination of food origin. Relevant evaluation approaches include principal component analysis, artificial neural networks, random forests, support vector machines, etc. The aim is to derive decision rules for the assignation of unknown samples to different classes. These decision rules are derived on the basis of samples whose origin is known—the training set. Typically, a reliable evaluation requires that the number of samples should be considerably larger than the number of features. However, in the framework of multiparameter mass spectrometry methods, the required ratio between sample and parameter numbers is inverted, with, e.g. 100 samples versus 10 000 features. In this paper, two approaches for the establishment of reliable decision rules in spite of low sample numbers are discussed.
      PubDate: 2019-04-24
       
  • Alternative designs for the assessment of homogeneity: use of
           characterisation data
    • Abstract: In order to reduce analysis cost and save samples, the homogeneity study of two titanium-certified reference materials was combined with the interlaboratory characterisation of that material. Samples were selected using a random-stratified sampling scheme and were sent to nine and 11 laboratories, respectively. The data were normalised to screen for trends in the production sequence, outliers and normality of the distribution of sample means. The non-normalised data were screened for outlying variances, and the uncertainty of homogeneity was evaluated using two-way analysis of variance. The uncertainty contributions determined were in all cases significant, but did usually not dominate the uncertainty of the assigned value. The findings were confirmed by a homogeneity study with a limited scope on one of the two materials. While the assessment of homogeneity using the approach was successful, the goal of reducing the consumption of samples and reducing analytical cost was only partially realised: a similar number of samples were consumed and 5 % – 10 % lower analytical cost than in a classical, separate homogeneity and characterisation study set-up was incurred.
      PubDate: 2019-04-24
       
  • Preparation of matrix reference material for quality assurance and control
           of pesticides analysis in olive oil
    • Abstract: The legislative requirements and the concern about the harmful effects of pesticide residues have encouraged National Institute of Standards to start development of a series of reference materials for food control to meet requirements of the regulatory authorities, improvement of the comparability and the quality of pesticides analysis and monitoring laboratories overall performance on a reliable, systematic and comparable basis. CRMs play a key role in quality control, precision studies, confirmation and validation of test methods. Comparability and the accuracy of the measurement results depend mainly on availability of certified reference materials appropriate for a particular application. This article gives an overview for complete production process of olive oil matrix reference material certified for organochlorine pesticides. A commercially available virgin olive oil was spiked with 23 pesticides in the range of 4 ng/g, and batch of 300 units was prepared. Characterization, stability, within- and between-samples homogeneity were determined according to ISO standards and guides. The results show that matrix reference material prepared under controlled metrologically valid procedures is valuable tool in the food analysis.
      PubDate: 2019-04-24
       
  • Quantitative scores for binary qualitative proficiency testing
    • Abstract: While z-scores provide participants with easy-to-interpret scores for quantitative proficiency tests, there is no universally accepted equivalent scoring method available for qualitative testing. Under the assumption that these tests follow a binomial distribution, it is possible to calculate scores that mimic the widely used z-scores and provide participants with insight into their performance level. We show that these scores, which we term a-scores, can be combined to provide a single score for multiple tests so that participants can monitor their performance over time, and discuss the use of the exact binomial test in place of uncertainty when there is no clear consensus.
      PubDate: 2019-04-23
       
  • Future requirements for non-decimal unit prefixes in chemical measurement
    • Abstract: The 2019 revision of the International System of Units (SI), including the redefinition of the mole, and the progress of analytical chemistry technologies allowing single-molecule resolution has brought into sharp focus the dilemma between expressing measurements of ultra-low quantities of elementary entities in terms of amount of substance or in terms of counting quantities. We should prefer the use of amount of substance for these measurements for a number of reasons including to allow intensive and extensive quantities in chemistry to be distinguished and to separate these measurements from those involving the counting of non-elementary entities. The discussion article highlights how a new, non-decimal approach to unit prefixes might in future enable amount of substance to be used usefully down to its natural limit—a single elementary entity. A new prefix symbol ‘σ’ is proposed to represent the multiplier 1/{NA}.
      PubDate: 2019-04-10
       
  • Traceability as a tool aiding food safety assurance on the example of a
           food-packing plant
    • Abstract: Enabling the possibility of “tracing” the route of a food product is a legal requirement for all participants of the food chain. It allows identifying and monitoring traffic and use of batches of raw materials, waste products, and finished products in the entire supply chain. The case study concerning a traceability system was conducted during BRCv7 (British Retail Consortium, Issue 7) audit made for packaged soybean oil. The analysis was based on the SOP (Standard Operating Procedure), HACCP (Hazard Analysis and Critical Control Points) procedure and records, including those concerning CCP (Critical Control Point), as well as the data from internal software Manufacturing WHM (WebHost Manager) Inquiries Version 5.2.8. and Traceability 2.1.0. for tracing batches of raw materials, additives, finished products, and clients. Verification revealed non-conformity in routine tests of the system, which was put on the list of corrective actions. Their correction was a prerequisite for meeting requirements of the standard and for system improvements. The corrective actions included complementation of the operational procedure for traceability of production and related documents with the records of supervision and verification of raw materials and packaging. The changes were introduced in the control procedure of machines and appliances in order to reduce the loss incurred while during packing oil. The employees were trained with regard to the changes introduced in the procedures, and the effectiveness of these actions was confirmed, which proved the necessity of the corrective actions undertaken.
      PubDate: 2019-04-09
       
  • Application of classification methods to analyze chemicals in drinking
           water quality
    • Abstract: To analyze drinking water dataset, various statistical methods have been applied, including discriminant analysis, logistic regression and cluster analysis, to construct models for the identification of important input variables. Among them decision trees are more flexible than other statistical classification methods because it provides us a complete path or frame to reach a specific decision with simplicity and ease of understanding about critical variables. This article describes the application of classification decision trees for the analysis of drinking water quality affecting variables and includes discussion about these based on various methods as well as their comparison to reach the best approach for the further analysis about understudy area. In this study, samples of filtered water are taken from 100 pumps located in different union councils of the Lahore city. The classification trees are constructed on the basis of input quality variables, and the results are reported in the form of confusion matrix. Four techniques, including Chi-square Automatic Interaction Detector, Exhaustive Chi-square Automatic Interaction Detector, Classification and Regression Tree and Quick Unbiased Efficient Statistical Tree, were used. Three experiments were conducted to get performance evaluation of the models by the number of misclassified units. The first method used complete dataset, the second one is based on the cross-validation, while the last one is based on the random subsampling.
      PubDate: 2019-04-09
       
  • Proficiency testing for total mercury in oyster with a metrologically
           traceable reference value from isotope dilution mass spectrometry:
           implications on laboratory practices using mercury analyzers
    • Abstract: Mercury is a toxic element of particular concern for the environment and human health, but its accurate analysis is challenging due to its unique physical and chemical properties. In order to enhance the quality and traceability of measurements, a proficiency testing (PT) program (MFDS-PT-101FM-2017) for mercury in oyster tissue has been conducted by the Ministry of Food and Drug Safety (MFDS) of Korea. A majority of the participating laboratories have used commercial mercury analyzers based on thermal decomposition amalgamation atomic absorption spectrometry (TDA–AAS). Good agreement between the participants’ results and the reference value (RV) was observed, where the RV is traceable to the International System of Units and verified for international equivalence. The results of this PT program support the participating laboratories in demonstrating their competence in quantitative analysis, and show the potential of commercial TDA–AAS systems for accurate mercury analysis.
      PubDate: 2019-04-02
       
 
 
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