Analytical method validation accuracy

Swartz, M. and Krull, I., Analytical method validation Accuracy in quantitation. LC-GC, 23, 46 (2005). 

Rozet, E., Wascotte, V., Lecouturier, N., Preat, V., Dewe, W., Boulanger, B., Hubert, P. Improvement of the decision efficiency of the accuracy profile by means of a desirability function for analytical methods validation application to a diacetyl-monoxime colorimetric assay used for the... 

Apart from the qualification dossiers provided by vendors there seems, at present, to be very little information published on the performance of an operational qualification for capillary electrophoresis (CE) instruments other than a chapter in Analytical Method Validation and Instrument Performance. The chapter, written by Nichole E. Baryla of Eli Lilly Canada, Inc, discusses the various functions (injection, separation, and detection) within the instrument and provides guidance on the type of tests, including suggested acceptance criteria, that may be performed to ensure the correct working of the instrument. These include injection reproducibility and linearity, temperature and voltage stability, detector accuracy, linearity, and noise. 

Analytical methods validation is a critical component of the entire company validation program. A method is not declared acceptable until a collaborative crossover study is conducted between two development laboratories and at least one quality control laboratory to ensure proper precision, accuracy, and efficiency. In the new world of outsourcing, it is imperative that an analytical crossover study be conducted between the client and supplier before any work is begun on dosage form development. 

Ensure adequacy and accuracy of analytical methods (validated methods). 

Test methods used in the laboratory are generally derived from pharmacopeias such as the US Pharmacopoeia, British Pharmacopoeia or European Pharmacopoeia. For test methods that are not from recognized pharmacopoeias, validation of the analytical methods is required. The validation includes testing for accuracy, specificity, ruggedness, robustness, precision, detection limit, quantitation limit and range. A discussion of analytical methods validation is presented in Section 9.6.5. 

Method validation is covered in the current Good Manufacturing Practices (cGMPs) under section 211.165(e) which indicates that The accuracy, sensitivity, specificity, and reproducibility of tests methods. .. shall be established and documented . Such validation and documentation may be accomplished in accordance with 211.194(a) (2) which includes the need to indicate the location of data that establish that the methods used in the testing of the sample meet proper standards of accuracy and reliability as applied to the product tested . Methods included in recognized standard references such as the current USP/NF are understood to be validated. The suitability of all testing methods used shall be verified under actual conditions of use (211.194). For new products for which methods are developed, analytical method validation as described in this chapter will be necessary for methods already included in the USP, method verification will suffice. 

The process of method validation (i.e., evaluation of the assay) affects the quality of the quantitative data directly [9 A Guide to Analytical Method Validation, Waters Corporation]. Through method validation, it is assured that the method developed is acceptable. Issues involved in the validation of a mass spectrometry method for quantitative analysis are similar to those in any other analytical technique. The validation involves undertaking a series of studies to demonstrate the limit of detection G OD) limit of quantitation (LOQ) linear range specificity within-day precision and accuracy and day-to-day precision and accuracy, specificity, and robustness of the method. All of these parameters must be determined with those commonly accepted good laboratory practices criteria that are applicable in the vafidation of analytical methods. 

Principles and Characteristics Whereas parameters most relevant to method development are considered to be accuracy, system precision, linearity, range, LOD, LOQ, sensitivity and robustness, method validation parameters are mainly bias, specificity, recovery (and stability of the analyte), repeatability, intermediate precision, reproducibility and ruggedness. However, method development and validation are highly related. Also, validation characteristics are not independent they influence each other. Acceptance criteria for validation parameters should be based on the specification limits of the test procedure. Quantitation and detection limits need a statement of the precision at their concentration levels. Procedures used for validation of qualitative methods are generally less involved than those for quantitative analytical methods. According to Riley [82], who has discussed the various parameters for validation of quantitative analytical methods, the primary statistical parameters that validate an analytical method are accuracy and precision. 

When an analytical method is being developed, the ultimate requirement is to be able to determine the analyte(s) of interest with adequate accuracy and precision at appropriate levels. There are many examples in the literature of methodology that allows this to be achieved being developed without the need to use complex experimental design simply by varying individual factors that are thought to affect the experimental outcome until the best performance has been obtained. This simple approach assumes that the optimum value of any factor remains the same however other factors are varied, i.e. there is no interaction between factors, but the analyst must be aware that this fundamental assumption is not always valid. 

Other features of an analytical method that should be borne in mind are its linear range, which should be as large as possible to allow samples containing a wide range of analyte concentrations to be analysed without further manipulation, and its precision and accuracy. Method development and validation require all of these parameters to be studied and assessed quantitatively. 

Option (Valid) presents a graph of relative standard deviation (c.o.v.) versus concentration, with the relative residuals superimposed. This gives a clear overview of the performance to be expected from a linear calibration Signal = A + B Concentration, both in terms of (relative) precision and of accuracy, because only a well-behaved analytical method will show most of the residuals to be inside a narrow trumpet -like curve this trumpet is wide at low concentrations and should narrow down to c.o.v. = 5% and rel. CL = 10%, or thereabouts, at medium to high concentrations. Residuals that are not randomly distributed about the horizontal axis point either to the presence of outliers, nonlinearity, or errors in the preparation of standards. 

In this article, an analytical method is defined as series of procedures from receipt of a sample to final determination of the residue. Validation is the process of verifying that a method is fit for purpose. Typically, validation follows completion of the development of a method. Validated analytical data are essential for monitoring of pesticide residues and control of legal residue limits. Analysts must provide information to demonstrate that a method intended for these purposes is capable of providing adequate specificity, accuracy and precision, at relevant analyte concentrations and in all matrices analyzed. 

Once the determinative or confirmatory method has been developed to take full advantage of the chemical properties of the analyte molecule, a study is necessary to prove that the method is valid. Criteria for method validation are outlined in guidelines from the US FDA, US EPA, and EU. A summary of the differences in regulatory requirements for method validation is provided in Table 3. The parameters addressed by all of the regulatory guidelines include accuracy, precision, sensitivity, specificity, and practicability. 

This analytical method provides very good precision and accuracy for the three parent herbicides over a 0.05-5.00 pgL range. Validation has been extended up to 20pgL-i. 

With respect to method application, once validation has been satisfactorily completed, there is little question that use of the analytical method in worker safety and re-entry studies falls under the full requirements of the GLP Standards. In addition, there should be an adequate level of quality control measurements taken in conjunction with the specimens so as to provide for a meaningful assessment of accuracy and precision, as well as verification of freedom from artifactual interferences. Along with these measurements there needs to be reasonably rigid data acceptance criteria in place (usually established during validation) which are consistently applied during the course of the specimen analytical phase of the study. 

Analytical methods, particularly those used by accredited laboratories, have to be validated according to official rules and regulations to characterize objectively their reliability in any special field of application (Wegscheider [1996] EURACHEM/WELAC [1993]). Validation has to control the performance characteristics of analytical procedures (see Chap. 7) such as accuracy, precision, sensitivity, selectivity, specificity, robustness, ruggedness, and limit values (e.g., limit of detection, limit of quantitation). 

For non-compendial procedures, the performance parameters that should be determined in validation studies include specificity/selectivity, linearity, accuracy, precision (repeatability and intermediate precision), detection limit (DL), quantitation limit (QL), range, ruggedness, and robustness [6]. Other method validation information, such as the stability of analytical sample preparations, degradation/ stress studies, legible reproductions of representative instrumental output, identification and characterization of possible impurities, should be included [7], The parameters that are required to be validated depend on the type of analyses, so therefore different test methods require different validation schemes. 

The validation process begun in Phase I is extended during Phase II. In this phase, selectivity is investigated using various batches of drugs, available impurities, excipients, and samples from stability studies. Accuracy should be determined using at least three levels of concentration, and the intermediate precision and the quantitation limit should be tested. For quality assurance evaluation of the analysis results, control charts can be used, such as the Shewart-charts, the R-charts, or the Cusum-charts. In this phase, the analytical method is refined for routine use. 

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