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Glossary of Analytical Chemistry Terms (GAT)

Glossary of Analytical Chemistry Terms (GAT). Bernd Wenclawiak. Glossary. Remark: Teaching and Learning terms is boring, but necessary! Why is it necessary to know the meaning of a term? Because a lot of expressions are not common in everyday life or might be interpreted differently

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Glossary of Analytical Chemistry Terms (GAT)

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  1. Glossary of Analytical Chemistry Terms (GAT) Bernd Wenclawiak In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  2. Glossary • Remark: Teaching and Learning terms is boring, but necessary! • Why is it necessary to know the meaning of a term?Because a lot of expressions are not common in everyday life or might be interpreted differently • In scientific and technical work it is necessary that all people use the same “language”. In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  3. Glossary • Who defines a term? • In chemistry there is IUPACIUPAC coordinates the international work of harmonization • In the field of metrology many different organizations work together: ISO, IEC , BIPM, OIML, IUPAC, IUPAP, IFCCThey jointly published the VIM In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  4. Glossary - Vocabularies • A Vocabulary contains general terms and definitions • International Vocabulary of Basic and General Terms in Metrology (VIM) • International Vocabulary of Terms in Legal Metrology (VIML). • Guide to the Expression of Uncertainty in Measurement (GUM) • ISO 3534-1:1993. “Statistics - Vocabulary and symbols - Part 1: Probability and general statistical terms”. • ISO 3534-2:1993. “Statistics - Vocabulary and symbols - Part 2: Statistical quality control”. • ISO 3534-3:1985. “Statistics - Vocabulary and symbols - Part 3: Design of experiments”. • ISO 8402:1994, “Quality - Vocabulary”. In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  5. Glossary • The bibliography comprises four different types of documents: • Guides • Standards • Books • Articles (in scientific journals) In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  6. Glossary - Standardization Organizations • International: ISO (www.iso.ch) • European: EN (www.cenorm.be) • German: DIN (www.din.de) • Great Britain: BS (www.bsi.org.uk) • United States: ASTM (www.astm.org) In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  7. Glossary – SI System • The International System of Units (SI) differentiates two classes of units: Base Units and Derived Units. • The Base Units are: Unit Quantity Symbol • metre length m • kilogram mass kg • second time s • ampere electric current A • kelvin thermodynamic temperature K • mole amount of substance mol • Candela luminous intensity cd  In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  8. Glossary - Important Organisations • European • EURACHEM - Co-operation for Analytical Chemistry in Europe • EUROLAB - Organization for Testing in Europe • EA - European Co-Operation for Accreditation • EUROMET - A European Collaboration in Measurement Standards IRMM Institute for Reference Materials and Measurements  • International • CITAC - Co-Operation on International Traceability in Analytical Chemistry • NIST – (US) National Institute of Standards and Technology In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  9. Glossary - Terms Related to: • General • Statistics • Validation • Measurement • Error • Uncertainty In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  10. Accreditation Accuracy Accuracy of measurement Accuracy of a Measuring Instrument Audit Bias Certification Fitness for Purpose Influence quantity Precision Quality Quality Assurance Quality Control Internal Quality Control Standard Trueness True Value Conventional True Value Glossary of General Terms In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  11. General Terms - Accreditation • Procedure by which an authoritative body gives formal recognition that a body or person is competent to carry out specific tasks (ISO/CASCO 193 (Rev. 2), & ISO Guide 2:1996) In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  12. General Terms - Accuracy • The closeness of agreement between the result of a measurement and the true value of the measurand • Accuracy is a measure which combines precision and trueness (i.e. the effects of random and systematic factors) • Suppose the results produced by the application of a method show zero or very low bias (i.e. are "true"), their accuracy becomes equivalent to their precision If the precision is poor, any particular result will be inaccurate • If a method shows a high bias, even results with a high precision are inaccurate In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  13. General Terms – Accuracy of Measurement • The closeness of the agreement between the result of a measurement and a true value of the measurand [VIM] • "Accuracy" is a qualitative concept. • The term "precision" should not be used for "accuracy". In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  14. General Terms - Accuracy (of a Measuring Instrument) • Ability of a measuring instrument to give responses close to a true value.[IUPAC Orange Book] • In this context accuracy is a qualitative concept. In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  15. General Terms - Audit • Quality Audit: ‘A systematic and independent examination to determine whether quality activities and related results comply with planned arrangements and whether these arrangements are implemented effectively and are suitable to achieve objectives’ (ISO 8402 - 1994). • External Audit also known as assessment • Internal • audit • review In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  16. General Terms - Bias • The difference between the expectation of the test results and an accepted reference value. • Characterises the systematic error in a given analytical procedure and is the (positive or negative) deviation of the mean analytical result from the (known or assumed) true value. [IUPAC Compendium of Chemical Technology, 1985] In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  17. General Terms - Certification • Procedure by which a third party gives written assurance that a product, process or service conforms to specified requirements(ISO/CASCO 193 (Rev. 2), 4.1.2, & ISO Guide2:1996, 15.1.2)  In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  18. General Terms – Fitness for Purpose • Degree to which data produced by a measurement process enables a user to make technically and administratively correct decisions for a stated purpose.[IUPAC Orange Book] In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  19. General Terms – Influence Quantity • A quantity that is not the measurand but that affects the result of the measurement [VIM]. In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  20. General Terms - Precision • The closeness of agreement between independent test results obtained under stipulated conditions • The precision statement can be made for any set of measurements which have been performed under stated experimental conditions which can be chosen freely • The precision of a set of results of measurements can be quantified as a standard deviation • Precise results on the same analyte are characterized by small statistical variability • This would then result in a small standard deviation, range or interquartile distance, all being measures of precision • Precision is a characteristic of a set of data In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  21. General Terms - Quality • „ ...quality is the totality of features of a unit as regards its suitability to fulfill specified and expected requirements.“ (ISO 8402) • A very important remark: “No data is better than poor data” In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  22. General Terms – Quality - What does that Mean? • „Quality means that the customer comes back, and not the product.“ • Quality and Liability are tightly connected In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  23. General Terms – Quality Assurance • All those planned and systematic activities implemented within the quality system, and demonstrated as needed, to provide adequate confidence that an entity will fulfil requirements for quality.[ISO 8402:1994] In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  24. General Terms – Quality Control • The operational techniques and activities that are used to fulfil requirements of quality. [ISO 8402:1994] In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  25. General Terms – Internal Quality Control • Set of procedures undertaken by laboratory staff for the continuous monitoring of operations and the results of measurements in order to decide whether results are reliable enough to be released.[IUPAC Orange Book] In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  26. General Terms – Standard • was used for widely adopted procedures, specifications, technical recommandations etc. • and also to chemical or physical standards, which are used for calibration purposes. • standard is used here only in the sense of writtenstandard In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  27. General Terms – Trueness • The closeness of agreement between the average value obtained from a large series of test results and the conventional true value • A true result is a result with little (or ideally no) systematical error without respect to the statistics of the series of results • Perfect trueness cannot be achieved, so trueness in its analytical meaning is always trueness within certain limits • These limits may be narrow at a high concentration level and wide at the trace level • It is important to note the difference between accuracy and trueness. • The lack of trueness is called bias In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  28. General Terms – True Value • Value which charcterizes a quantity perfectly defined in the conditions which exist when that quantity is considered. • The true value is a theoretical concept and, in general, cannot be known exactly • It is a value that would be obtained by a perfect measurement • True values are by nature indeterminate In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  29. General Terms – Conventional True Value • Value attributed to a particular quantity and accepted, sometimes by convention, as having an uncertainty appropriate for a given purpose • A result obtained by using several independent methods in several expert laboratories on one measurand is regarded as conventional true value of a quantity even if it is not the "true" value • A conventional true value is in general, regarded as sufficiently close to the true value for the difference to be insignificant for the given purpose. In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  30. Arithmetic mean  Distribution functions Normal distribution Rectangular distribution Triangular distribution Poisson distribution Binomial distribution Estimate Probabilty Standard Deviation Sample Standard Deviation Standard deviation of the mean Relative Standard Deviation (RSD) Glossary on Statistical Terms In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  31. Statistical Terms – Distribution Functions • Normal distribution continuous distribution • Rectangular distribution • Triangular distribution • Poisson distribution discrete function • Binomial distribution discrete function In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  32. Calibration Curve linear least squares calibration Cross Reactivity Discrimination Discrimination Threshold Limiting Mean Limit of Detection Minimum Detectable Net Concentration Limit of Decision Limit of Determination Limit of Quantitation Limit of Reporting Linearity Proficiency Testing Range - Measuring and working Recovery Reference Material Certified Reference Material Repeatability Repeatability of Results of Measurements Repeatability of a Measuring Instrument Repeatability Standard Deviation Repeatability Limit r Reproducibility Reproducibility Standard Deviation Reproducibility Limit R Ruggedness Test Selectivity Selectivity in Analysis Sensitivity Specificity Validation Method Validation Verification Glossary on Validation Terms In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  33. Validation Method Validation Instrument Validation Verification Proficiency Testing Limiting Mean Limit of Detection Minimum Detectable Net Concentration Limit of Quantitation Validation Terms In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  34. Validation Terms • Calibration Curve • Graphical representation of measuring signal as a function of quantity of analyte. [AOAC] • Linear least squares calibration • calibration with the method of minimizing the least squares In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  35. Validation Terms • Linearity • Defines the ability of the method to obtain test results proportional to the concentration of analyte. • The Linear Range is by inference the range of analyte concentrations over which the method gives test results proportional to the concentration of the analyte. [AOAC] In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  36. Measurement Terms • Measurand • Measurement • Measurement Procedure • Method of Measurement • Response Time • Result of a Measurement In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  37. Measurement Terms - Measurement Standard • measurement standard is used to describe chemical or physical standards used for calibration purposes such as: chemicals of established purity and their corresponding solutions of known concentration, UV filter, weights, etc. They are also called: reference material In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  38. Error Terms • Error of Measurement • Random Error • Systematic Error • False Negatives/Positives In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  39. Error Terms - Error (of a Result) • The test result minus the conventional true value • error is the sum of random and systematic errors • If a measurement is repeated, each individual result will have its own associated error In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  40. Error Terms– False Negatives / Positives • For qualitative methods the false positives/negatives rate may be determined. • Data from a confirmatory method comparison should be provided if such method(s) is applicable to the same matrix(es) and concentration range(s). • In the absence of a method comparison, populations of negative and positive fortified samples must be analysed. In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  41. Uncertainty Terms • Uncertainty (of Measurement) • Standard Uncertainty • Combined Standard Uncertainty • Expanded Uncertainty • Coverage Factor • Type A evaluation (of uncertainty) • Type B evaluation (of uncertainty) In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  42. Uncertainty Terms - Measurement Uncertainty • Parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand • Uncertainty sets the limits within which a result is regarded accurate, I.e. precise and true • Uncertainty of measurement comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of the results of series of measurements and can be characterized by experimental standard deviations • The other components, which can also be characterized by standard deviations, are evaluated from assumed probability distributions based on experience or other information. In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

  43. Uncertainty Terms – Traceability • Property of the result of a measurement or the value of a standard whereby it can be related with: • a stated uncertainty, • to stated references (usually national or international standards) In:Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

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