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Sunday, June 28, 2009

ASEAN GUIDELINES FOR VALIDATION OF ANALYTICAL PROCEDURES

VALIDATION OF ANALYTICAL PROCEDURES
1. Introduction
The objective of validation of an analytical procedure is to demonstrate that it is suitable
for its intended purpose.
This guideline is to provide the guidance and recommendation of validation of the
analytical procedures for submission as part of registration applications within ASEAN.
The document mainly adopts two ICH guidelines “Q2A: Validation of Analytical
Methods: Definitions and Terminology, 27 October 1994” and “ICH Q2B: Validation of
Analytical Procedure: Methodology, 6 November 1996. The methodology applied for
biological and biotechnological products may be approached differently than chemical
entities.
All relevant data collected during validation and formulae used for calculating validation
characteristics should be submitted and discussed as appropriate. Well-characterized
reference materials, with document purity, should be used throughout the validation study.
The degree of purity depends on the intended use.
In practice, it is usually possible to design the experimental work such that the appropriate
validation characteristics can be considered simultaneously to provide a sound, over all
knowledge of the capabilities of the analytical procedure, for instance: specificity,
linearity, range, accuracy and precision. The compendial methods are not required to be
validated, but merely verify their suitability under actual conditions of use.
For Asean requirement : All data related to the validation characteristics should be
submitted to the Drug Regulatory Authority together with the respective acceptance
criteria.
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.
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 behavior, 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.
- 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
Intermediate Precision
Reproducibility
Specificity
Detection Limit
Quantitation Limit
Linearity
Range
Robustness
Each of these validation characteristics is defined in the 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 changes. Certain other
changes may require validation as well.



- 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
3. Analytical Performance Characteristics
3.1 SPECIFICITY
An investigation of specificity should be conducted during the validation of identification
tests, the determination of impurities and the assay. The procedures used to demonstrate
specificity will depend on the intended objective of the analytical procedure. It is not
always possible to demonstrate that an analytical procedure is specific for a particular
analyte (complete discrimination). In this case a combination of two or more analytical
procedures is recommended to achieve the necessary level of discrimination.
3.1.1. Identification
Suitable identification tests should be able to discriminate between compounds of closely
related structures which are likely to be present. The discrimination of a procedure may be
confirmed by obtaining positive results (perhaps by comparison with a known reference
material) from samples containing the analyte, coupled with negative results from samples
which do not contain the analyte. In addition, the identification test may be applied to
materials structurally similar to or closely related to the analyte to confirm that a positive
response is not obtained. The choice of such potentially interfering materials should be
based on sound scientific judgement with a consideration of the interferences that could
occur.
3.1.2. Assay and Impurity Test(s)
For chromatographic procedures, representative chromatograms should be used to
demonstrate specificity and individual components should be appropriately labelled.
Similar considerations should be given to other separation techniques. Critical separations
in chromatography should be investigated at an appropriate level. For critical separations,
specificity can be demonstrated by the resolution of the two components which elute
closest to each other. In cases where a non-specific assay is used, other supporting
analytical procedures should be used to demonstrate overall specificity. For example,
where a titration is adopted to assay the drug substance for release, the combination of the
assay and a suitable test for impurities can be used. The approach is similar for both assay
and impurity tests:
3.1.2.1 Impurities are available
For the assay , this should involve demonstration of the discrimination of the analyte in the
presence of impurities and/or excipients; practically, this can be done by spiking pure
substances (drug substance or drug product) with appropriate levels of impurities and/or
excipients and demonstrating that the assay result is unaffected by the presence of these
materials (by comparison with the assay result obtained on unspiked samples).
For the impurity test, the discrimination may be established by spiking drug substance or
drug product with appropriate levels of impurities and demonstrating the separation of
these impurities individually and/or from other components in the sample matrix.
3.1.2.2 Impurities are not available
If impurity or degradation product standards are unavailable, specificity may be
demonstrated by comparing the test results of samples containing impurities or degradation
products to a second well-characterized procedure e.g.: pharmacopoeial method or other
validated analytical procedure (independent procedure). As appropriate, this should include
samples stored under relevant stress conditions:
light, heat, humidity, acid/base hydrolysis and oxidation.
- for the assay, the two results should be compared.
- for the impurity tests, the impurity profiles should be compared.
Peak purity tests may be useful to show that the analyte chromatographic peak is not
attributable to more than one component (e.g., diode array, mass spectrometry).
3.2 LINEARITY
A linear relationship should be evaluated across the range (see section 3.3) of the analytical
procedure. It may be demonstrated directly on the drug substance (by dilution of a standard
stock solution) and/or separate weighings of synthetic mixtures of the drug product
components, using the proposed procedure. The latter aspect can be studied during
investigation of the range. Linearity should be evaluated by visual inspection of a plot of
signals as a function of analyte concentration or content. If there is a linear relationship,
test results should be evaluated by appropriate statistical methods, for example, by
calculation of a regression line by the method of least squares. In some cases, to obtain
linearity between assays and sample concentrations, the test data may need to be subjected
to a mathematical transformation prior to the regression analysis. Data from the regression
line itself may be helpful to provide mathematical estimates of the degree of linearity.
The correlation coefficient, y-intercept, slope of the regression line and residual sum of
squares should be submitted. A plot of the data should be included. In addition, an analysis
of the deviation of the actual data points from the regression line may also be helpful for
evaluating linearity.
Some analytical procedures, such as immunoassays, do not demonstrate linearity after any
transformation. In this case, the analytical response should be described by an appropriate
function of the concentration (amount) of an analyte in a sample.
For the establishment of linearity, a minimum of 5 concentrations is recommended.
Other approaches should be justified.
3.3 RANGE
The specified range is normally derived from linearity studies and depends on the intended
application of the procedure. It is established by confirming that the analytical procedure
provides an acceptable degree of linearity, accuracy and precision when applied to samples
containing amounts of analyte within or at the extremes of the specified range of the
analytical procedure. The following minimum specified ranges should be considered:
- for the assay of a drug substance or a finished (drug) product: normally from 80 to 120
percent of the test concentration;
- for content uniformity, covering a minimum of 70 to 130 percent of the test
concentration, unless a wider more appropriate range, based on the nature of the dosage
form (e.g., metered dose inhalers), is justified;
- for dissolution testing: +/-20 % over the specified range; e.g., if the specifications for a
controlled released product cover a region from 20%, after 1 hour, up to 90%, after 24
hours, the validated range would be 0-110% of the label claim.
- for the determination of an impurity: from the reporting level of an impurity 1 to 120%
of the specification; for impurities known to be unusually potent or to produce toxic or
unexpected pharmacological effects, the detection/quantitation limit should be
commensurate with the level at which the impurities must be controlled.
Note: for validation of impurity test procedures carried out during development, it may be
necessary to consider the range around a suggested (probable) limit;
- if assay and purity are performed together as one test and only a 100% standard is used,
linearity should cover the range from the reporting level of the impurities 1 to 120% of the
assay specification;
1 see chapters “Reporting Impurity Content of Batches” of the corresponding ICHGuidelines:
“Impurities in New Drug Substances” and “Impurities in New Drug Products”
3.4 ACCURACY
Accuracy should be established across the specified range of the analytical procedure.
3.4.1. Assay
3.4.1.1 Drug Substance
Several methods of determining accuracy are available:
a) application of an analytical procedure to an analyte of known purity (e.g. reference
material);
b) comparison of the results of the proposed analytical procedure with those of a second
well-characterized procedure, the accuracy of which is stated and/or
defined (independent procedure, see 3.1.2.);
c) accuracy may be inferred once precision, linearity and specificity have been established.
3.4.1.2 Drug Product
Several methods for determining accuracy are available:
a) application of the analytical procedure to synthetic mixtures of the drug product
components to which known quantities of the drug substance to be analysed have been
added;
b) in cases where it is impossible to obtain samples of all drug product components, it may
be acceptable either to add known quantities of the analyte to the drug product or to
compare the results obtained from a second, well characterized procedure, the accuracy of
which is stated and/or defined (independent procedure, see 3.1.2.).
c) accuracy may be inferred once precision, linearity and specificity have been
established.
3.4.2. Impurities (Quantitation)
Accuracy should be assessed on samples (drug substance/drug product) spiked with known
amounts of impurities. In cases where it is impossible to obtain samples of certain
impurities and/or degradation products, it is considered acceptable to compare results
obtained by an independent procedure (see 3.1.2.). The response factor of the drug
substance can be used.
It should be clear how the individual or total impurities are to be determined e.g.,
weight/weight or area percent, in all cases with respect to the major analyte.
3.4.3 Recommended Data
Accuracy should be assessed using a minimum of 9 determinations over a minimum of 3
concentration levels covering the specified range (e.g. 3 concentrations/3 replicates each of
the total analytical procedure).
Accuracy should be reported as percent recovery by the assay of known added amount of
analyte in the sample or as the difference between the mean and the accepted true value
together with the confidence intervals.
3.5 PRECISION
Validation of tests for assay and for quantitative determination of impurities includes an
investigation of precision.
3.5.1 Repeatability
Repeatability should be assessed using:
a) a minimum of 9 determinations covering the specified range for the procedure (e.g. 3
concentrations/3 replicates each) or
b) a minimum of 6 determinations at 100% of the test concentration.
3.5.2 Intermediate Precision
The extent to which intermediate precision should be established depends on the
circumstances under which the procedure is intended to be used. The applicant should
establish the effects of random events on the precision of the analytical procedure. Typical
variations to be studied include days, analysts, equipment, etc. It is not considered
necessary to study these effects individually. The use of an experimental design (matrix) is
encouraged.
3.5.3 Reproducibility
Reproducibility is assessed by means of an inter-laboratory trial. Reproducibility should be
considered in case of the standardization of an analytical procedure, for instance, for
inclusion of procedures in pharmacopoeias. These data are not part of the marketing
authorization dossier.
3.5.4 Recommended Data
The standard deviation, relative standard deviation (coefficient of variation) and
confidence interval should be reported for each type of precision investigated.
3.6 DETECTION LIMIT
Several approaches for determining the detection limit are possible, depending on whether
the procedure is a non-instrumental or instrumental. Approaches other than those listed
below may be acceptable.
3.6.1 Based on Visual Evaluation
Visual evaluation may be used for non-instrumental methods but may also be used with
instrumental methods.
The detection limit is determined by the analysis of samples with known concentrations of
analyte and by establishing the minimum level at which the analyte can be reliably
detected .
3.6.2. Based on Signal-to-Noise
This approach can only be applied to analytical procedures which exhibit baseline noise.
Determination of the signal-to-noise ratio is performed by comparing measured signals
from samples with known low concentrations of analyte with those of blank samples and
establishing the minimum concentration at which the analyte can be reliably detected. A
signal-to-noise ratio between 3 or 2:1 is generally considered acceptable for estimating the
detection limit.
3.6.3 Based on the Standard Deviation of the Response and the Slope
The detection limit (DL) may be expressed as:
DL = 3.3 σ/S
where σ = the standard deviation of the response
S = the slope of the calibration curve
The slope S may be estimated from the calibration curve of the analyte. The estimate of S
may be carried out in a variety of ways, for example:
3.6.3.1 Based on the Standard Deviation of the Blank
Measurement of the magnitude of analytical background response is performed by
analyzing an appropriate number of blank samples and calculating the standard deviation
of these responses.
3.6.3.2 Based on the Calibration Curve
A specific calibration curve should be studied using samples containing an analyte in the
range of DL. The residual standard deviation of a regression line or the standard deviation
of y-intercepts of regression lines may be used as the standard deviation.
3.6.4 Recommended Data
The detection limit and the method used for determining the detection limit should be
presented. If DL is determined based on visual evaluation or based on signal to noise ratio,
the presentation of the relevant chromatograms is considered acceptable for justification.
In cases where an estimated value for the detection limit is obtained by calculation or
extrapolation, this estimate may subsequently be validated by the independent analysis of a
suitable number of samples known to be near or prepared at the detection limit.
3.7 QUANTITATION LIMIT
Several approaches for determining the quantitation limit are possible, depending on
whether the procedure is a non-instrumental or instrumental. Approaches other than those
listed below may be acceptable.
3.7.1 Based on Visual Evaluation
Visual evaluation may be used for non-instrumental methods but may also be used with
instrumental methods. The quantitation limit is generally determined by the analysis of
samples with known concentrations of analyte and by establishing the minimum level at
which the analyte can be quantified with acceptable accuracy and precision.
3.7.2. Based on Signal-to-Noise Approach
This approach can only be applied to analytical procedures that exhibit baseline noise.
Determination of the signal-to-noise ratio is performed by comparing measured signals
from samples with known low concentrations of analyte with those of blank samples and
by establishing the minimum concentration at which the analyte can be reliably quantified.
A typical signal-to-noise ratio is 10:1.
3.7.3. Based on the Standard Deviation of the Response and the Slope
The quantitation limit (QL) may be expressed as:
QL = 10 σ/S
where σ= the standard deviation of the response
S = the slope of the calibration curve
The slope S may be estimated from the calibration curve of the analyte. The estimate of S
may be carried out in a variety of ways for example:
3.7.3.1 Based on Standard Deviation of the Blank
Measurement of the magnitude of analytical background response is performed by
analyzing an appropriate number of blank samples and calculating the standard deviation
of these responses.
3.7.3.2 Based on the Calibration Curve
A specific calibration curve should be studied using samples, containing an analyte in the
range of QL. The residual standard deviation of a regression line or the standard deviation
of y-intercepts of regression lines may be used as the standard deviation.
3.7.4 Recommended Data
The quantitation limit and the method used for determining the quantitation limit should be
presented. The limit should be subsequently validated by the analysis of a suitable number
of samples known to be near or prepared at the quantitation limit.
3.8 ROBUSTNESS
The evaluation of robustness should be considered during the development phase and
depends on the type of procedure under study. It should show the reliability of an analysis
with respect to deliberate variations in method parameters. If measurements are
susceptible to variations in analytical conditions, the analytical conditions should be
suitably controlled or a precautionary statement should be included in the procedure. One
consequence of the evaluation of robustness should be that a series of system suitability
parameters (e.g., resolution test) is established to ensure that the validity of the analytical
procedure is maintained whenever used. Examples of typical variations are:
- stability of analytical solutions,
- extraction time
In the case of liquid chromatography, examples of typical variations are
- influence of variations of pH in a mobile phase,
- influence of variations in mobile phase composition,
- different columns (different lots and/or suppliers),
- temperature,
- flow rate.
In the case of gas-chromatography, examples of typical variations are
- different columns (different lots and/or suppliers),
- temperature,
- flow rate.
3.9 SYSTEM SUITABILITY TESTING
System suitability testing is an integral part of many analytical procedures. The tests are
based on the concept that the equipment, electronics, analytical operations and samples to
be analyzed constitute an integral system that can be evaluated as such. System suitability
test parameters to be established for a particular procedure depend on the type of procedure
being validated. They are especially important in the case of chromatographic methods. See
Pharmacopoeias for additional information.
4. GLOSSARY
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.
2. 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.
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.
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 Repeatability
Repeatability expresses the precision under the same operating conditions over a short
interval of time. Repeatability is also termed intra-assay precision.
4.2 Intermediate precision
Intermediate precision expresses within-laboratories variations: different days, different
analysts, different equipment, etc.
4.3 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.
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 deliberate variations in method parameters and provides an indication of its
reliability during normal usage.

1 comment:

Dr Raj said...

very useful one for the beginners. will be happy to read this in the pdf format (no strain to eyes).

Cheers
N. Rajasekar, Ph.D.,(IISc)