Validation of methods

When the analyst has properly defined the analytical problem to be solved (see Chapter 1), he has to select an adapted analytical procedure. The selection and the development of the procedure will be based on the investigation of the scientific literature and on the experience of the analyst and of colleagues. The general equipment of the laboratory and the scope of its activity will also influence the choice of method and the selected approach. Several books deal with the most important methods applied by analytical chemists. Examples of their application are given and the reader should refer to them. A basic book, mainly foreseen for students in analytical chemistry, but also very valuable for senior analysts, has been published recently by Kellner et al. [18]. 

All analytical methods are composed of a succession of actions sampling, storage and preservation of a representative test sample of the material pretreatment of a portion of the test sample for the quantification calibration of the instrument and signal final determination of the test sample calculations and presentation of results. 

The selection of the analytical method is usually done on the basis of the already available instrumental possibilities of the laboratory and the experience of the staff. The analytical procedure consists in the transformation of the test sample in order to convert the analyte into a physical or chemical form, which allows determining accurately the amount of a substance present in this test sample. 

Selecting and developing a method consists in the choice of individual steps, to make them compatible and to develop tools to verify that the individual steps and the entire 

It must be stressed here that method validation is as important and complex in microbiology. Similar steps and precautions exist. An important part of the book edited by Lightfoot and Maier [6] deals with all these aspects from development and validation of the method, validation of instruments and supplies up to the use of control charts. The reader is referred to these guidelines and to sections 2.3.3 and 2.4.3. 

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The "method of standard additions" has been employed as a technique for standardization of atomic absorption analyses of metals In biological fluids (13,21) In this procedure, several concentrations of standard analyte are added to samples of the biological fluid to be analyzed The calibration curve which Is obtained after additions of the standard analyte to the biological fluid should parallel that obtained when aqueous standards are analyzed Extrapolation of the standard additions curve back to a negative Intercept on the abscissa furnishes an estimate of the concentration of the analyte In the original sample (21) This technique Is helpful In assessing the validity of methods of trace metal analysis (11,13,58) However, In the author s opinion, the "method of standard additions" Is neither practical nor reliable as a routine method for standardization... 

Air Force. 1990. Development and validation of methods for applying pharmacokinetic data in risk assessment Volume n. Trichloroethylene. Wright-Patterson Air Force Base, OH U.S. Air Force, Air Force Systems Command, Harry G. Armstrong Medical Research Laboratory, Human Systems Division. NTIS No. AD-A237 366. 

Validation of methods for specific uses, and developing new or improved techniques and methods. 

In contrast to multi-analyte/multi-matrix methods, a more or less complete validation of methods with limited scope is possible. For this reason, TC 275 decided that... 

SFE instrument development has greatly been stimulated by the desire of the Environmental Protection Agency (EPA) to replace many of their traditional liquid-solvent extraction methods by SFE with carbon dioxide. In the regulatory environment, EPA and FDA approved SFE and SFC applications are now becoming available. Yet, further development requires interlaboratory validation of methods. Several reviews describe analytical SFE applied to polymer additives [89,92,324]. 

Sablayrolles C, Montrejaud-Vignoles M, Benanou D, Patria L, Treilhou M (2005) Development and validation of methods for the trace determination of phthalate in sludge and vegetables. J Chrom 1072 233-242... 

Phelps,M.E.,Huang,S.C.,Hoffman,E.J.eta/.Tomographic measurement of local cerebral glucose metabolic rate in humans with 18F 2-fluoro-2-deoxy-D-glucose validation of method. Ann. Neurol. 6 371-388,1979. 

For the sake of comparison and mutual validation of methods for measuring large follow-up reaction rate constants, it is interesting to apply different methods to the same system. Such a comparison between high-scan-rate ultramicroelectrode cyclic voltammetry, redox catalysis, and laser flash photolysis has been carried out for the system depicted in Scheme 2.25, where methylacridan is oxidized in acetonitrile, generating a cation radical that is deprotonated by a base present in the reaction medium.20... 

Member States shall ensure that the validation of methods of analysis used within the context of official control of foodstuffs by the laboratories referred to in Article 7 of Directive 89/397/EEC comply whenever possible with the provisions of paragraphs 1 and 2 of the Annex to Council Directive 85/591/EEC of 23 December 1985 concerning the introduction of Community methods of sampling and analysis for the monitoring of foodstuffs intended for human consumption.7... 

Technology transfer can be demonstrated by several different options including comparative testing, co-validation of methods between laboratories, complete (or partial) re-validation by the receiving unit and a waiver of transfer procedures. 

Validation of methods for quantitative determination of impurities includes precision studies. Repeatability is generally assessed by analysis of the same sample or samples prepared by the same analyst in replicate assays within a short duration of time. Repeatability should be assessed using (i) a minimum of nine determinations covering the specified range for the procedure (e.g., three concentrations/three replicates each) or (ii) a minimum of six determinations at 100% of the test concentration. Repeatability is evaluated by averaging the mean results from replicate assays and calculating the standard deviation (SD) and RSD. Repeatability of the method can be stated as either SD or RSD values. If an instrument is required for assay performance, then the same instrument should be used for the replicate assays. 

M. Blanco, J. Coello, A. Eustaquio, H. Itturriaga and S. Maspoch, Development and validation of methods for the determination of miokamycin in various pharmaceutical preparations by use of near infrared reflectance spectroscopy, Analyst, 124, 1089-1092 (1999). 

If no standard methods exist or if they are not appropriate, laboratoiy developed or other non-standard methods that are suitable for the special task and which are validated can be used. Validation of methods is an important task in the laboratoiy (see chapter 11). 

Technical competence is dealt with only in accreditation and refers both to the methodology nsed and the peisormel involved. In accreditation, validation of methods and expression of imcer-tainty are of major importance as well as the calibration of eqnipment and traceability of measnrements. 

Documentation of process and validation of methods (including cleaning procedures) and facilities. Required regulatory submissions. 

The main objective of validation of an analytical procedure is to demonstrate that the procedure is suitable for its intended purpose. The procedures presented in this SOP provide basic guidelines for the validation of methods for microbiological assay, estimation of the number of microorganisms, detection of indicators of objectionable microorganisms, validation of preservative efficacy testing, and validation of the sterility testing and endotoxin test (LAL test). 

Because of the gaps in our present understanding of carcinogenesis and the paucity of human data for most chemicals, risk assessments for chemicals are generally more uncertain than risk assessments for radiation. Tb improve such assessments, there is pai ticular need for further development and validation of methods for extrapolation from animal data to man and further refinement of methods for evaluating variations in hmnan susceptibility and human exposure, e.g., biological markers. 

Gunderson, E. C. and Anderson, . C., "Development and Validation of Methods for Sampling and Analysis of Workplace Toxic Substances," November, 1979, Final Report on NIOSH Contract 210-... 

Thompson, M., Ellison, S., and Wood, R. (2002), Harmonised guidelines for singlelaboratory validation of methods of analysis, IUPAC Technical Report, Pure Appl. Chem., 74,835-855. 

CX/MAS 02/12 (2002), Codex Alimentarius Commission, Codex Committee on Methods of Analysis and Sampling (FAO/WHO), Validation of methods through the use of results from proficiency testing schemes, agenda item 8c of the 24th session, Budapest, Hungary, Nov. 18-22, 2002. 

To avoid confusion, the terms and parameters used in the validation of methods, for example, as used in Figure 3, must be clearly and unambiguously defined. This glossary contains the recommended definitions and corresponding descriptions and is based on the various standards and publications summarised in the Bibliography. This is not exhaustive and it is recommended that the lUPAC Orange Book be consulted if required. 

Method validation has received considerable attention in the literature and from industrial committees and regulatory agencies. The international standard ISO/ IEC [1] requires validation of nonstandard methods, laboratory designed/devel-oped methods, standard methods used outside their intended scope, and amplifications and modifications of standard methods to confirm that the methods are suitable for their intended use. The Guidance on the Interpretation of the EN 45000 Series of Standards and ISO/IEC Guide 25 includes a chapter on the validation of methods [2] with a list of nine validation parameters. The International Conference on Harmonization (ICH) of Technical Requirements for the... 

Present-day analytical laboratories are increasingly under pressure to supply objective evidence of their technical competence, of the reliability of their results and performance, and to seek formal certification or accreditation. This pressure may come from the laboratory s customers (e.g., industry and national bodies) but may also be due to scientific considerations. A QM system in place, validation of methods, uncertainty evaluation, the use of primary standards and CRMs, participation in ILCs, and PT, all serve to assure and demonstrate the quality of measurements. Compared to, say, 30 years ago, the stability of the equipment now available is much improved, and a greater range of RMs for method validation and calibration is accessible. Nevertheless, to achieve mutual (international) acceptance of various bodies of evidence for QA activities, a number of protocols have been developed. The most widely recognized protocols used in chemical measurements and testing are the ISO Guide 9000 2000, ISO/IEC 17025 2005, and OECD Guidelines for GLP, as well as its national and sector equivalents. 

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