Wenclawiak, B.: Glossary of Analytical Chemistry Terms© Springer-Verlag Berlin Heidelberg 2003 In: Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance

In: Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance in Analytical Chemistry – Training and Teaching

Wenclawiak, B.: Glossary of Analytical Chemistry Terms © Springer-Verlag Berlin Heidelberg 2003

Bernd Wenclawiak

Glossary of Analytical Chemistry Terms (GAT)



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”.



Glossary

Who defines a term? In chemistry there is IUPAC

IUPAC 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



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”.



Glossary

The bibliography comprises four different types of documents: Guides Standards Books Articles (in scientific journals)



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)



Glossary – SI System The International System of Units (SI)

differentiates two classes of units: Base Units and Derived Units.

The Base Units are: Unit QuantitySymbol

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



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



Glossary - Terms Related to:

General Statistics Validation Measurement Error Uncertainty



Glossary of General Terms 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



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)



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



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".



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.



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



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]



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)



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]



General Terms – Influence Quantity

A quantity that is not the measurand but that affects the result of the measurement [VIM].



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



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”



General Terms – Quality - What does that Mean?

„Quality means that the customer comes back, and not the product.“

Quality and Liability are tightly connected



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]



General Terms – Quality Control

The operational techniques and activities that are used to fulfil requirements of quality. [ISO 8402:1994]



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]



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



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



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



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.



Glossary on Statistical Terms

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)



Statistical Terms – Distribution Functions

Normal distribution continuous distribution Rectangular distribution Triangular distribution

Poisson distribution discrete function Binomial distribution discrete function



Glossary on Validation Terms 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



Validation Method Validation Instrument Validation Verification Proficiency Testing

Limiting Mean Limit of Detection Minimum Detectable

Net Concentration Limit of Quantitation

Validation Terms



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



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]



Measurement Terms

Measurand Measurement Measurement Procedure Method of Measurement Response Time Result of a Measurement



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



Error Terms

Error of Measurement Random Error Systematic Error False Negatives/Positives



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



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.



Uncertainty Terms

Uncertainty (of Measurement) Standard Uncertainty Combined Standard Uncertainty Expanded Uncertainty Coverage Factor Type A evaluation (of uncertainty) Type B evaluation (of uncertainty)



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.



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)

Documents

Wenclawiak, B.: Glossary of Analytical Chemistry Terms© Springer-Verlag Berlin Heidelberg 2003 In: Wenclawiak, Koch, Hadjicostas (eds.) Quality Assurance