Method validation is the process used to confirm that the analytical procedure employed for a specific test is suitable for its intended use. Results from method validation can be used to judge the quality, reliability and consistency of analytical results; it is an integral part of any good analytical practice. Analytical methods need to be validated or revalidated
The validity of a specific method should be demonstrated in laboratory experiments using samples or standards that are similar to unknown samples analyzed routinely. The preparation and execution should follow a validation protocol, preferably written in a step-by-step instruction format. Possible steps for a complete method validation are listed in Table 1. This proposed procedure assumes that the instrument has been selected and the method has been developed. It meets criteria such as ease of use; ability to be automated and to be controlled by computer systems; costs per analysis; sample throughput; turnaround time; and environmental, health and safety requirements.
ISO/IEC 17025 definition: ‘The confirmationby examination and the provision of objective evidencethat the particular requirements for a specific intended use are fulfilled’
– analytical requirement
– what will test method be used for? why are measurements required?
– experimental data from method validation study
– information on method performance
– comparison of requirement with experimental evidence
Can the method deliver results that are fit for a particular purpose?
Without validation there can be no assurance that results will be fit for purpose
– is the proposed method likely to be fit for purpose?
– including standard/published methods which have been validated by others
– verify suitability for analytical requirement
– verify own ability to match published data
- laboratory shall use appropriate methods and procedures for all tests within its scope
- methods must meet customer requirements
– preference for standard methods (international/national standards)
– ‘laboratory shall confirm that it can properly operate standard methods before introducing the tests’
– laboratory-developed methods may be used if they are validated
– (standard -§5.4.2)
– laboratory designed/developed
– standard methods outside normal scope
– amplified/modified standard methods
- measurement uncertainty, detection limit, selectivity, linearity, repeatability/reproducibility, robustness
– what will the data be used for?
– quantitative or qualitative
– likely concentration
– nature (matrix)
– destructive vs non-destructive test
– am I measuring what I think I’m measuring? are there any interferences?
– how close are the results of replicate measurements made on the same sample?
– how close are the results to the ‘right’answer
– range of analyte concentrations that can be measured reliably
– limit of detection, limit of quantitation
– control necessary for each stage of the procedure
|Parameter||Type of Analysis|
|Qualitative||Major Component||Trace Analysis||Physical Property|
|Specficity / selectivity|
|Limit of Detection|
|Limit of Quantitation|
Major component : analyte concentration in range 1-100%
Trace analysis : analyte concentration less than 100 mg/kg
– YES - method is fit for purpose
– NO - more development required
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