1. Analytical Procedure:
The analytical procedure refers to the way of performing the analysis. It should describe in detail the steps necessary to perform each analytical test. This may include but is not limited to: the sample, the reference standard and the reagents preparations, use of the apparatus, generation of the calibration curve, use of the formulae for the calculation, etc.
Specificity is the ability to assess unequivocally the analyte in the presence of components which may be expected to be present. Typically these might include impurities, degradants,matrix, etc.
Lack of specificity of an individual analytical procedure may be compensated by other supporting analytical procedure(s).
This definition has the following implications:
Identification: to ensure the identity of an analyte.
Purity Tests: to ensure that all the analytical procedures performed allow an accurate statement of the content of impurities of an analyte, i.e. related substances test, heavy metals, residual solvents content, etc.
Assay (content or potency): to provide an exact result which allows an accurate statement on the content
or potency of the analyte in a sample.
3. Accuracy :
The accuracy of an analytical procedure expresses the closeness of agreement between the value which is accepted either as a conventional true value or an accepted reference value and the value found.
This is sometimes termed trueness.
The precision of an analytical procedure expresses the closeness of agreement (degree of scatter) between a series of measurements obtained from multiple sampling of the same homogeneous sample under the prescribed conditions. Precision may be considered at three levels: repeatability, intermediate precision and reproducibility.
Precision should be investigated using homogeneous, authentic samples. However, if it is not possible to obtain a homogeneous sample it may be investigated using artificially prepared samples or a sample solution.
The precision of an analytical procedure is usually expressed as the variance, standard deviation or coefficient of variation of a series of measurements.
Repeatability expresses the precision under the same operating conditions over a short interval of time. Repeatability is also termed intra-assay precision
Intermediate precision expresses within-laboratories variations: different days, different analysts, different equipment, etc.
Reproducibility expresses the precision between laboratories (collaborative studies,usually applied to standardization of methodology).
The detection limit of an individual analytical procedure is the lowest amount of analyte in a sample which can be detected but not necessarily quantitated as an exact value.
The quantitation limit of an individual analytical procedure is the lowest amount of analyte in a sample which can be quantitatively determined with suitable precision and accuracy. The quantitation limit is a parameter of quantitative assays for low levels of compounds in sample matrices, and is used particularly for the determination of impurities and/or degradation products.
The linearity of an analytical procedure is its ability (within a given range) to obtain test results which are directly proportional to the concentration (amount) of analyte in the sample.
The range of an analytical procedure is the interval between the upper and lower concentration (amounts) of analyte in the sample (including these concentrations) for which it has been demonstrated that the analytical procedure has a suitable level of precision, accuracy and linearity.
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
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Reference: ICH Topic Q 2 (R1) Validation of Analytical Procedures:Text and Methodology