VALIDATION OF ANALYTiCAL PROCEDURES: DEFINITIONANDTERMINOLOGY

1. Introduction
This document presents a discussion of the characteristics for consideration during the validation
of the analytical procedures included as part of registration applications submitted within the
European Union (EU), Japan and USA. This document does not necessarily seek to cover the
testing that may be required for registration in, or export to, other areas of the world. Furthermore,
this text presentation serves as a collection of terms, and their definitions, and is not intended to
provide direction on how to accomplish validation. These terms and definitions are meant to bridge
the differences that often exist between various compendia and regulators of the EU, Japan and
USA,
The objective of validation of an analytical procedure is to demonstrate that it is suitable for its
intended purpose. A tabular summation of the characteristics applicable to identification, control
of impurities and assay procedures is included. Other analytical procedures may be considered
in future additions to this document.
2. Types of Analytical Procedures to be Validated
The discussion of the validation of analytical procedures is directed to the four most common
types of analytical procedures:
- Identification tests.
- Quantitative tests for impurities content.
- Limit tests for the control of impurities.
- Quantitative tests of the active moiety in samples of drug substance or drug product or other
selected component(s) in the drug product.
Although there are many other analytical procedures, such as dissolution testing for drug products
or particle size determination for drug substances, these have not been addressed in the initial text
on validation of analytical procedures. Validation of these additional analytical procedures is equally
important to those listed herein and may be addressed in subsequent documents.
A brief description of the types of tests considered in this document is provided below,
- Identification tests are intended to ensure the identity of an analyte in a sample. This is
normally achieved by comparison of a property of the sample (e.g., spectrum,
chromatographic behaviour, chemical reactivity, etc) to that of a reference standard.
- Testing for impurities can be either a quantitative test or a limit test for the impurity in a
sample. Either test is intended to accurately reflect the purity characteristics of the sample.
Different validation characteristics are required for a quantitative test than for a limit test.
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- Assay procedures are intended to measure the analyte present in a given sample. In the context
of this document, the assay represents a quantitative measurement of the major component(s)
in the drug substance. For the drug product, similar validation characteristics also apply when
assaying for the active or other selected component(s). The same validation characteristics may
also apply to assays associated with other analytical procedures (e.g., dissolution).
The objective of the analytical procedure should be clearly understood since this will govern the
validation characteristics which need to be evaluated. Typical validation characteristics which
should be considered are listed below:
Accuracy
Precision
Repeatability
htermediate Precision
Specificity
Detection Limit
Quantitation Limit
Linearity
Range
Each of these validation characteristics is defined in the attached Glossary. The table lists those
validation characteristics regarded as the most important for the validation of different types of
analytical procedures. This list should be considered typical for the analytical procedures cited but
occasional exceptions should be dealt with on a case-by-case basis. It should be noted that
robustness is not listed in the table but should be considered at an appropriate stage in the
development of the analytical procedure.
Furthermore revalidation may be necessary in the following circumstances:
changes in the synthesis of the drug substance;
changes in the composition of the finished product;
changes in the analytical procedure;
The degree of revalidation required depends on the nature of the cha-nges. Certain other
changes may require validation as well.
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*
TABLE
.
Type of analytical lDENTIFICATION
procedure
I
characteristics I
Accuracy
Precision
Repeatability
Interm. Precision
Specificity (2)
Detection Limit
Quantitation Limit
Linearity
Range
1-
1~
1-
1-
1-
TESTING FOR
IMPURITIES
quantitat. limit
+-
+-
+(1) -
+ +
- (3) +
+-
+-
+-
ASSAY
- dissolution
(measurement only)
- contenffpotency
+
+
+ (1)
+
+
+
signifies that this characteristic is not normally evaluated
+ signifies that this characteristic is normally evaluated
(1) in cases where reproducibility (see glossary) has been performed, intermediate precision is
not needed
(2) lack of specificity of one analytical procedure could be compensated by other supporting
analytical procedure(s)
(3) may be needed in some cases
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1.
2.
3.
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
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.
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.
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.
4. PRECISION
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.
4.1.
4.2.
4.3.
Repeatability
Repeatability expresses the precision under the same operating conditions over a short interval of
time, Repeatability is also termed intra-assay precision.
Intermediate precision
Intermediate precision expresses within-laboratories variations: different days, different analysts,
different equipment, etc.
Reproducibility
Reproducibility expresses the precision between laboratories (collaborative studies, usually applied
to standardization of methodology).
5. DETECTION LIMIT
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.
6. QUANTITATION LIMIT
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.
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7. LINEARITY
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.
8. RANGE
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.
9. ROBUSTNESS
The robustness of an analytical procedure is a measure of its capacity to remain unaffected by small, but