Analytical method validation aspects

Analytical method validation forms the first level of QA in the laboratory. Analytical quality assurance (AQA) is the complete set of measures a laboratory must undertake to ensure that it is able to achieve high-quality data continuously. Besides the use of validation and/or standardized methods, these measures are effective IQC procedures (use of reference materials, control charts, etc.), with participation in proficiency testing schemes and accreditation to an international standard, normally ISO/IEC 17025 [4]. Method validation and the different aspects of QA form the subject of Section 8.2.3. 

Analytical method validation—Aprerequisite for any validation involving the analysis of the microbiological, physical, or chemical aspects of materials is the use of analytical methods that have been demonstrated to be reliable and reproducible. No meaningful assessment of product or material quality can be made without the... 

Analytical method validation has developed within the pharmaceutical industry over the years in order to produce an assurance of the capabilities of an analytical method. A recent text on validation of analytical techniques has been published by the international Conference on Harmonisation (ICH) [19]. This discusses the four most common analytical procedures (1) identification test, (2) quantitative measurements for content of impurities, (3) limit test for the control of impurities and (4) quantitative measurement of the active moiety in samples of drug substance or drug product or other selected components of the drug product. As in any analytical method, the characteristics of the assay are determined and used to provide quantitative data which demonstrate the analytical validation. The reported validation data for CE are identical to those produced by an LC or GC method [11] and are derived from the same parameters, i.e. peak time and response. Those validation parameters featured by the ICH (Table 1) are derived from the peak data generated by the method. Table 1 also indicates those aspects of a CE method (instrumentation and chemistry), peculiar to the technique, which can affect the peak data and highlights factors which can assist the user in demonstrating the validation parameters. 

In summary, official German analytical methods for pesticide residues are always validated in several laboratories. These inter-laboratory studies avoid the acceptance of methods which cannot readily be reproduced in further laboratories and they do improve the ruggedness of analytical procedures applied. The recently introduced calibration with standards in matrix improves the trueness of the reported recovery data. Other aspects of validation (sample processing, analyte stability, extraction efficiency) are not considered. 

One aspect of specimen analysis that often occurs and should be highlighted is the situation that arises when a study has been initiated (protocol has been signed), but the analytical procedure has not yet been determined or worked out, or perhaps has not been fully validated by the performing laboratory. In this case, the approved protocol should fully describe the situation, and once the method has been developed and/or validated an approved protocol amendment should be issued, thus formalizing the inclusion of the analytical methodology. Likewise, during the validation process or during the study itself, if there is an analytical method modification then the protocol also needs to be formally amended. 

Validation is the process of proving that a method is acceptable for its intended purpose. It is important to note that it is the method, not the results, that are validated (Chapter 10). The most important aspect of any analytical method is the quality of the data it ultimately produces. The development and validation of a new analytical method may therefore be an iterative process. Results of validation studies may indicate that a change in the procedure is necessary, which may then require revalidation. Before a method is routinely used, it must be validated. There are a number of criteria for validating an analytical method, as different performance characteristics will require different validation criteria. 

Aspects which are generally relevant to validate analytical methods Precision... 

It is beneficial to develop generic methods, this means methods that are already validated for some aspects, e.g., EOF stability and freedom of matrix interferences. Generic methods that are suitable to separate a number of analytes can be found in CE, especially due to the high separation efficiency. Some aspects, like specificity and repeatability, are still analyte specific, but the entire method validation is substantially speeded up when a generic method already exists. 

Finally, process analytics methods can be used in commercial manufacturing, either as temporary methods for gaining process information or troubleshooting, or as permanent installations for process monitoring and control. The scope of these applications is often more narrowly defined than those in development scenarios. It will be most relevant for manufacturing operations to maintain process robustness and/or reduce variability. Whereas the scientific scope is typically much more limited in permanent installations in production, the practical implementation aspects are typically much more complex than in an R D environment. The elements of safety, convenience, reliability, validation and maintenance are of equal importance for the success of the application in a permanent installation. Some typical attributes of process analytics applications and how they are applied differently in R D and manufacturing are listed in Table 2.1. 

In analytical chemistry, validation of the analytical methods is of utmost importance [4,5]. One of the aspects of this validation is the robustness of analytical methods against variations in experimental circumstances. The term experimental circumstances is very broad it might even include inter-laboratory variation. In this book, only intra-laboratory experimental conditions are considered. No explicit attention is given to inter-laboratory variations, although some of the presented methodology might be useful in that area. 

Together with the fast development of analytical methodologies, great importance is nowadays attached to the quality of the measurement data. Besides the necessary reporting of any result with its MU and traceability of the results to stated standards or references (Section 8.2.2), a third crucial aspect of analytical methods of whichever type is their status of validation. It is internationally recognized that validation is necessary in analytical laboratories. However, less is known about what is validation and what should be validated, why validation is important, when and by whom validation is performed, and finally, how it is carried out practically. This Chapter has tried to answer these questions. 

Method validation is a term used for the suite of procedures to which an analytical method is subjected to provide objective evidence that the method, if used in the manner specified, will produce results that conform to the statement of the method validation parameters. Like many aspects quality assurance, method validation is of a relative nature. As with the concept of fitness for purpose, a method is validated for a particular use under particular circumstances. If those circumstances vary, then the method would need to be re-validated at least for the differences. Common sense should be used, and the analysts should use his or her skill and experience to decide what aspects of a method require validation and to what extent. The goal of satisfying client requirements is prominent in most published definitions of method validation, some of which are listed below ... 

How analytical methods deal with interferences is one of the more ad hoc aspects of method validation. There is a variety of approaches to studying interference, from adding arbitrary amounts of a single interferent in the absence of the analyte to establish the response of the instrument to that species, to multivariate methods in which several interferents are added in a statistical protocol to reveal both main and interaction effects. The first question that needs to be answered is to what extent interferences are expected and how likely they are to affect the measurement. In testing blood for glucose by an enzyme electrode, other electroactive species that may be present are ascorbic acid (vitamin C), uric acid, and paracetamol (if this drug has been taken). However, electroactive metals (e.g., copper and silver) are unlikely to be present in blood in great quantities. Potentiometric membrane electrode sensors (ion selective electrodes), of which the pH electrode is the... 

Method validation covers a number of aspects of an analytical method that have already been evaluated in the course of development and use. The values of the calibration parameters must be known to use the method to analyze a particular sample, and any serious deviations from the measurement model should have been discovered. In addition, however, every method should undergo a robustness study as the practicality of the method may ultimately depend on how rugged it is. 

Different approaches may be used to validate the sample preparation component of the dissolution test. However, it is important to understand that the objective of validation is to demonstrate that the procedure is suitable for its intended purpose. For example, one of the strategies will demonstrate the validity of different aspects of sample preparation during method development (prior to the formal method validation exercise). As a result, the final validation experiments will confirm the work done during method development. The strategy that will be followed for the method development and validation process will depend on the culture, expertise, and strategy of the analytical laboratory. 

Huber has published two validation reference books for the analytical laboratory [7,8]. The first one covers all validation aspects of an analytical laboratory, including equipment, analytical methods, reference compounds, and personnel qualification. The second covers the validation of computerized and networked systems. 

Abstract Although the validation process necessary to ensure that an analytical method is fit for purpose is universal, the emphasis placed on different aspects of that process will vary according to the end use for which the analytical procedure is designed. It therefore becomes difficult to produce a standard method validation protocol which will be totally applicable to all analytical methods. It is probable that far more than 30% of the methods... 

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