Validation of an Analytical Procedure

Method validation is the process of showing that a new procedure or an existing procedure applied to a new type of sample meets specifications and is acceptable for its intended purpose. Standard methods published by government and private agencies are validated by multiple labs before they are published. In pharmaceutical chemistry, method validation requirements include studies of selectivity, accuracy, precision, linearity, range, robustness, limit of detection, and limit of quantitation. Selectivity, accuracy, and precision were mentioned in Section 5-1. 

Another goal of validation is to show that a method is robust, which means that it is not affected by small changes in conditions. For example, a robust chromatographic procedure gives reliable results despite small changes in solvent composition, pH, buffer concentration, temperature, injection volume, and detector wavelength. 

Only —1% of measurements for a blank are expected to exceed the detection limit. However, 50% of measurements for a sample containing analyte at the detection limit will be below the detection limit. There is a 1% chance of concluding that a blank has analyte above the detection limit. If a sample contains analyte at the detection limit, there is a 50% chance of concluding that analyte is absent because its signal is below the detection limit. Curves in this figure are Student s f distributions, which are broader than the Gaussian distribution. 

After estimating the detection limit from previous experience with the method, prepare a sample whose concentration is 1 to 5 times the detection limit. 

Measure the signal from n blanks (containing no analyte) and find the mean 

---

Liere P, Akwa Y, Engerer SW, Eychenne B, Pianos A, et al. 2000. Validation of an analytical procedure to measure trace amounts of neurosteroids in brain tissue by gas chromatography-mass spectrometry. J Chromatog B 739 301-312. 

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). 

Validation of an analytical procedure is the process by which it is established, by laboratory studies, that the performance characteristics of the procedure meet the Ill... 

The aim of validation of an analytical procedure is to demonstrate that the method employed in any product testing, such as the identification, control of impurities, assay, dissolution, particle size, water content, or residual solvents, is validated in the most important characteristics. Identification tests, quantitative tests for impurities content, limit tests for control of impurities, and quantitative tests of the active moiety in samples of pharmaceutical product are the most common types of analytical procedures that validation addresses [1]. 

The validation of an analytical procedure produces performance parameters of a well-behaved and well-conditioned system/instrument (including defined variations) which are more or less snapshots of the combination procedure/system. In order to routinely confirm the suitability of the integrated measurement instrumentation used with a given procedure, system suitability test parameters should be defined on the basis of the validation results and robustness studies. Larger variations under routine conditions or multiple laboratories should also be taken into consideration. 

It follows that the common criteria of validation should be made more specific in terms of measurement assurance. It is (the index of) accuracy that requires overriding consideration among the characteristics of analytical performance if quality of the results is primarily kept in mind. Other performance characteristics are desirable to ensure that a methodology is well-established and fully understood, but validation of an analytical procedure on those criteria seems impractical also in view of the lack of corresponding requirements as is commonly the case. (Strictly speaking, there is no validation unless a particular requirement has been set.)... 

Validation of an analytical procedure is a process required to demonstrate that the procedure is suitable for its intended use (see Chapter 12). Almost all analytical tests require some type of validation. The amount and type of validation will depend on the test procedure. Validation is necessary before an analytical test can become a test procedure in the QC laboratory. 

Validation of an analytical procedure to measure trace amounts 5 3. 

Validation of an analytical procedure is the process by which the performance characteristics of the procedure are shown to meet the requirements for the intended application. Validation is very important to meet the requirements of regulatory agencies, such as, the FDA (Food and Drug Administration). It is also necessary to ensure that the method can work reproducibly and reliably in QC (Quality Control) laboratories for support of manufacturing. 

Wylie FM, Torrance H, Anderson RA, Oliver JS. Drugs in oral fluid. Part 1. Validation of an analytical procedure for licit and illicit drugs in oral fluid. Forensic Sci Int 2005 150(2-3) 191-8. 

It is now necessary to discuss in more detail the performance criteria one can use to evaluate different methods and to describe the validation of different analytical procedures so that you can decide whether or not a given method will fulfil your own particular requirements. In many cases, there will be no method which is entirely suitable for your purpose. In such cases, it will be necessary to adapt an existing method. Before use, such an amended method will need to be validated to ensure that the modifications introduced do not produce erroneous results (see Section 4.6). 

The analytical method validation activity is not a one-time study. This is illustrated and summarized in the life cycle of an analytical procedure in Figure 1. An analytical... 

Validation is needed to demonstrate that the analytical method complies with established criteria for different performance characteristics [82]. When these different characteristics are being evaluated individually, this is generally done for the analytical method as such—where the input is the purified or isolated analyte and the output is the analytical result. However, MU covers the whole analytical procedure, starting from the original sample lot. The assessment of MU (see Section 8.2.2) is in line with the so-called modular validation approach. Modular validation refers to the modularity of an analytical procedure divided up into several sequential steps needed to analyze the material. These may be sample preparation, analyte extraction, and analyte determination (Figure 7). Each step in the procedure can be seen as an analytical system and can thus be validated separately and combined... 

However, other analytical procedures, such as dissolution testing for dosage form or particle size determination for drug substance, are required for validation of analytical procedures. The revalidation of an analytical procedure is possible when, in particular circumstances, it could show changes in the synthesis of the drug substance, the composition of the finished product, or the analytical procedure. However, certain other changes may require validation as well. 

Method validation should confirm that the analytical procedure employed for a specific test is suitable for its intended use. The validation of an analytical method... 

Full validation of an analytical method usually comprises an examination of its characteristics in interlaboratory method performance studies. However, before a method is subjected to validation by collaborative studies, the method must be validated by a single laboratory, usually by the laboratory that developed or modified this particular measurement procedure. Method validation can be described as the set of tests used to establish and document the performance characteristics of a method and against which it may be judged, thereby demonstrating that the method is fit for a particular analytical purpose. 

The validity of an analytical method can be verified only by laboratory studies. Therefore, documentation of the successful completion of such studies is a basic requirement for determining whether a method is suitable for its intended applications. Appropriate documentation should accompany any proposal for new or revised compendial analytical procedures. 

In the absence of suitable reference materials, the procedure should be tested using different sample weights and also measuring recoveries of element added at the beginning of the procedure. It must be remembered, however, that these criteria although necessary, are not sufficient, for the complete demonstration of the validity of the analytical procedure. The application of an independent (different in all respects of sample treatment and analyte quantitation) analytical method to a homogeneous practice sample would provide very useful confirmation of method reliability. 

Of course, it must be guaranteed that the analytical procedure is consistently in a validated state. This can be achieved by monitoring appropriate SST results. Another possibility is to perform (regularly) supplementary investigations such as further intermediate precision studies, which can be included in the routine analysis. With this approach, it is possible to supplement and extend existing information and to take the very important time factor into proper consideration. Information can be obtained on the long-term behavior of an analytical procedure and therefore on the reliability in routine use, for example, better estimates on the true (long term) analytical variability. 

The USP definition of robustness equals that of the ICH (3) The robustness of an analytical procedure is a measure of its capacity to remain unaffected by small, but deliberate variations in method parameters and provides an indication of its reliability during normal usage. A robustness test is the experimental setup used to evaluate method robustness. It quantifies the insensitivity of the results for a method transfer to another laboratory or instrument. The ICH guidelines also state that One consequence of the evaluation of robustness should be that a series of system suitability parameters (eg., resolution tests) is established to ensure that the validity of the analytical procedure is maintained whenever used (3). 

In the pharmaceutical industry, analytical procedures are the necessary eyes and ears of all experiments performed and data produced. If the quality of an analytical procedure is inadequate, the resulting measurements may be questionable and the scientific validity of the study conclusions may be compromised. Therefore, appropriate evaluation of the data from an analytical procedure is critical from both the statistical and scientific perspectives. 

Methods, (other than pharmacopoeial methods), should be validated. Typical validation characteristics which should be considered, include accuracy, precision, (repeatability and intermediate precision), specificity, detection limit, quantitation limit, linearity and range. Robustness should be considered at an appropriate stage in the development of an analytical procedure. 

Assay validation characterizes the assay performance so that the significance of the measured assay values obtained is readily understood [75]. Test methods should be validated when important decisions are to be based on the data generated [30]. Thus, the extent of method validation depends on the stage of clinical supply manufacture. The key elements of assay validation for a method are to establish reliability, the intra- and interlaboratory test variation, and relevance, the meaning of the results for a specific purpose [19]. The robustness of an analytical procedure (according to the ICH-Validation of Analytical Methods, 1993) is its measured capacity to be unaffected by small variations in controlled parameters and reliability under normal usage [35]. 

This validation parameter can be defined as the ability of an analytical procedure to yield test results which are directly proportional to the concentration of the analyte in the sample . Linearity is evaluated across the range of the method. Five different concentrations are recommended by the ICH Guidance. For example, for a typical... 

Easier validation of the different steps of an analytical procedure. 

Since standard compounds may not be readily available, control of these parameters and validation of the analytical procedure can be very difficult. Usually, agreement with the independently determined average DS, the absence of side products, and high recovery of material (determined by addition of an internal standard) are used for control. GLC/FID allows calculation of the relative molar composition of monomers by correcting their peak areas according to the ECR concept, as already mentioned. "- ... 

Successfiil completion of the validation results in a method that can reliably be used to characterize real samples. Ongoing validation activities may also be necessary during the routine utilization of an analytical procedure, as well as the revalidation of the analytical procedure, as certain operational aspects of the method are changed during its routine and continuous application. 

Elucidation of how the general principles underlying the concept of validation should be expressed in practice is an evolving process, as exemplified by the ongoing evolution of validation requirements for bioanalytical assays in the pharmaceutical industry (Shah 1992, 2000 FDA 2001 Viswanathan 2007). The complementary principle of fitness for purpose (Section 9.2) applies not only to the assay method but also to the validation process itself. Procedures that are considered to be fit for purpose in validation of an analytical method to be used in drug development, for example, need not necessarily apply to, e.g., methods used to screen pesticide residues in foodstuffs. As noted in Section 9.2, this point of view appears to be consistent with the definition of validation applied to all measurements (ISO 1994) Validation Confirmation by examination and provision of objective evidence that the particular requirements for a specified intended use are fulfilled. Of course, some basic principles are common to all validation schemes. 

In all these applications, isotope ratio data are produced, which are interpreted on an absolute or relative basis and which have an impact on our daily life, whether this is in science (e.g., age of an artifact), in society (e.g., provenance of food), or in public safety (e.g., neutron shielding in nuclear power plants). To ensure that these data are reliable and accurate, some specific requirements have to be fulfilled. The main requirement is that all these measurement results are comparable, which means that the corresponding results can be compared and differences between the measurement results can be used to draw further conclusions. This is only possible if the measurement results are traceable to the same reference [25]. This in turn can only be realized by applying isotopic reference materials (IRMs) for correction for bias and for validation of the analytical procedure. Whereas in earlier days only experts in mass spectrometry were able to deliver reproducible isotope ratio data, nowadays many laboratories, some of which may even have never been involved with mass spectrometry before, produce isotope ratio data using inductively coupled plasma mass spectrometry (ICP-MS). Especially for such users, IRMs are indispensable to permit proper method validation and reliable results. The rapid development and the broad availability of ICP-MS instrumentation have also led to an expansion of the research area and new elements are under investigation for their isotopic variations. In this context, all users require IRMs to correct for instrumental mass discrimination or at least to allow isotope ratio data to be related to a commonly accepted basis. 

---