Q2(R1) Validation of 
Analytical Procedures: 
Text and Methodology  
Guidance for Industry 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Drug Evaluation and Research (CDER) 
Center for Biologics Evaluation and Research (CBER) 
 
November 20051 
ICH 
 
 
1 This guidance, Q2(R1) Validation of Analytical Procedures: Text and Methodology (Q2(R1)),  
was initially published as two separate guidances, Q2A Text on Validation of Analytical Procedures (March 
1995)(Q2A) and Q2B Validation of Analytical Procedures: Methodology (May 1997)(Q2B). In November 2005, the 
International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) 
incorporated Q2B on methodology with the parent document Q2A and retitled the combined document Q2(R1). In 
October 2021, FDA likewise incorporated Q2B with the parent document Q2A and retitled the combined document 
Q2(R1). This guidance consists of the previously published FDA guidances Q2A and Q2B. It is the same, in 
substance, as those two guidances, and it is the same, in substance, as the November 2005 ICH Q2(R1) guideline. 
 
    
Q2(R1) Validation of 
Analytical Procedures: 
Text and Methodology  
Guidance for Industry 
 
Additional copies are available from: 
Office of Communications, Division of Drug Information  
Center for Drug Evaluation and Research 
Food and Drug Administration 
10001 New Hampshire Ave., Hillandale Bldg., 4th Floor  
Silver Spring, MD 20993-0002  
Phone: 855-543-3784 or 301-796-3400; Fax: 301-431-6353 
Email: druginfo@fda.hhs.gov  
https://www.fda.gov/drugs/guidance-compliance-regulatory-information/guidances-drugs 
and/or 
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Center for Biologics Evaluation and Research 
 Food and Drug Administration 
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Email: ocod@fda.hhs.gov 
https://www.fda.gov/vaccines-blood-biologics/guidance-compliance-regulatory-information-biologics/biologics-guidances     
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Drug Evaluation and Research (CDER) 
Center for Biologics Evaluation and Research (CBER) 
November 20052 
ICH 
 
2 This guidance, Q2(R1) Validation of Analytical Procedures: Text and Methodology (Q2(R1)),  
was initially published as two separate guidances, Q2A Text on Validation of Analytical Procedures (March 
1995)(Q2A) and Q2B Validation of Analytical Procedures: Methodology (May 1997)(Q2B).  In November 2005, 
the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) 
incorporated Q2B on methodology with the parent document Q2A and retitled the combined document Q2(R1). In 
October 2021, FDA likewise incorporated Q2B with the parent document Q2A and retitled the combined document 
Q2(R1). This guidance consists of the previously published FDA guidances Q2A and Q2B. It is the same, in 
substance, as those two guidances, and it is the same, in substance, as the November 2005 ICH Q2(R1) guideline. 
 
   
Q2(R1) 
Document History 
 
Document Codification  Document Name  Date 
Q2A  Q2A Text on Validation of  March 1995 
Analytical Procedures 
Q2B  Q2B Validation of Analytical  May 1997 
Procedures: Methodology 
Q2(R1)  Validation of Analytical  November 20053 
Current Version  Procedures: Text and 
(Combines Q2A and Q2B in  Methodology Q2(R1)  
a single integrated guidance)   
 
 
3
 As noted above, in October 2021, FDA incorporated Q2B Validation of Analytical Procedures: Methodology (May 
1997)(Q2B) on methodology with the parent document Q2A Text on Validation of Analytical Procedures (March 
1995)(Q2A) and retitled the combined document Q2(R1) Validation of Analytical Procedures: Text and 
Methodology (Q2(R1). This guidance consists of the previously published FDA guidances, Q2A and Q2B. It is the 
same, in substance, as those two guidances, and it is the same, in substance, as the November 2005 ICH Q2(R1) 
guideline. 
 
  Contains Nonbinding Recommendations 
 
FOREWORD 
 
The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for 
Human Use (ICH) has the mission of achieving greater regulatory harmonization worldwide to 
ensure that safe, effective, and high-quality medicines are developed, registered, and maintained 
in the most resource-efficient manner. By harmonizing the regulatory expectations in regions 
around the world, ICH guidelines have substantially reduced duplicative clinical studies, 
prevented unnecessary animal studies, standardized safety reporting and marketing application 
submissions, and contributed to many other improvements in the quality of global drug 
development and manufacturing and the products available to patients.  
 
ICH is a consensus-driven process that involves technical experts from regulatory authorities and 
industry parties in detailed technical and science-based harmonization work that results in the 
development of ICH guidelines. The commitment to consistent adoption of these consensus-
based guidelines by regulators around the globe is critical to realizing the benefits of safe, 
effective, and high-quality medicines for patients as well as for industry. As a Founding 
Regulatory Member of ICH, the Food and Drug Administration (FDA) plays a major role in the 
development of each of the ICH guidelines, which FDA then adopts and issues as guidance to 
industry.  
 
NOTE 
 
 
This guidance consists of two previously published FDA guidances that were developed and 
finalized before the implementation of FDAs good guidance practices regulation (21 CFR 
10.115).4   
 
4 As noted above, in October 2021, FDA incorporated Q2B Validation of Analytical Procedures: Methodology 
(May 1997)(Q2B) on methodology with the parent document Q2A Text on Validation of Analytical Procedures 
(March 1995)(Q2A) and retitled the combined document Q2(R1) Validation of Analytical Procedures: Text and 
Methodology (Q2(R1). This guidance consists of the previously published FDA guidances, Q2A and Q2B, without 
any substantive changes. 
 
  Contains Nonbinding Recommendations 
 
TABLE OF CONTENTS 
 
 
 
PART I:  
TEXT ON VALIDATION OF ANALYTICAL PROCEDURES ............................................. 1 
I.  INTRODUCTION............................................................................................................. 1 
II.  TYPES OF ANALYTICAL PROCEDURES TO BE VALIDATED........................... 2 
APPENDIX A.  GLOSSARY ....................................................................................................... 5 
 
PART II: 
VALIDATION OF ANALYTICAL PROCEDURES: METHODOLOGY ............................ 7 
I.  INTRODUCTION............................................................................................................. 7 
II.   SPECIFICITY (1) ............................................................................................................. 2 
A. Identification (1.1) ............................................................................................................................. 2 
B. Assay and Impurity Test(s) (1.2) ...................................................................................................... 2 
1. Impurities are available (1.2.1) ........................................................................................................ 2 
2. Impurities are not available (1.2.2) .................................................................................................. 3 
III.  LINEARITY (2) ................................................................................................................ 3 
IV.  RANGE (3) ........................................................................................................................ 4 
V.   ACCURACY (4) ................................................................................................................ 4 
A. Assay (4.1) ........................................................................................................................................... 4 
1. Drug substance (4.1.1) ..................................................................................................................... 5 
2. Drug product (4.1.2) ........................................................................................................................ 5 
B. Impurities (Quantitation) (4.2) ......................................................................................................... 5 
C. Recommended Data (4.3) .................................................................................................................. 5 
VI.   PRECISION (5) ................................................................................................................. 6 
A. Repeatability (5.1) .............................................................................................................................. 6 
B. Intermediate Precision (5.2) .............................................................................................................. 6 
C. Reproducibility (5.3) .......................................................................................................................... 6 
D. Recommended Data (5.4) .................................................................................................................. 6 
VII.   DETECTION LIMIT (6) .................................................................................................. 6 
A. Based on Visual Evaluation (6.1) ...................................................................................................... 7 
B. Based on Signal-to-Noise (6.2) .......................................................................................................... 7 
C. Based on the Standard Deviation of the Response and the Slope (6.3) ......................................... 7 
1. Based on the standard deviation of the blank (6.3.1) ....................................................................... 7 
2. Based on the calibration curve (6.3.2) ............................................................................................. 7 
i  Contains Nonbinding Recommendations 
 
D. Recommended Data (6.4) .................................................................................................................. 7 
VIII.   QUANTITATION LIMIT (7) .......................................................................................... 8 
A. Based on Visual Evaluation (7.1) ...................................................................................................... 8 
B. Based on Signal-to-Noise (7.2) .......................................................................................................... 8 
C. Based on the Standard Deviation of the Response and the Slope (7.3) ......................................... 8 
1. Based on standard deviation of the blank (7.3.1) ............................................................................. 8 
2. Based on the calibration curve (7.3.2.) ............................................................................................ 9 
D. Recommended Data (7.4) .................................................................................................................. 9 
IX.   ROBUSTNESS (8) ............................................................................................................ 9 
X.   SYSTEM SUITABILITY TESTING (9) ...................................................................... 10 
ii  Contains Nonbinding Recommendations 
 
Q2(R1) Validation of Analytical Procedures: Text and Methodology  
Guidance for Industry 
 
 
This guidance represents the current thinking of the Food and Drug Administration (FDA or Agency) on 
this topic.  It does not establish any rights for any person and is not binding on FDA or the public.  You 
can use an alternative approach if it satisfies the requirements of the applicable statutes and regulations.  
To discuss an alternative approach, contact the FDA office responsible for this guidance as listed on the 
title page.   
 
 
5
PART I  
 
TEXT ON VALIDATION OF ANALYTICAL PROCEDURES 
 
 
I.  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, Japan, and United States. 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 European Union, Japan, and United States. 
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. 
 
In general, FDAs guidance documents do not establish legally enforceable responsibilities.  
Instead, guidances describe the Agencys current thinking on a topic and should be viewed only 
as recommendations, unless specific regulatory or statutory requirements are cited.  The use of 
the word should in Agency guidances means that something is suggested or recommended, but 
not required.  
 
 
 
5 Part I of this guidance was developed within the Expert Working Group (Quality) of the International Council for 
Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) and has been subject to 
consultation by the regulatory parties, in accordance with the ICH process.  This document has been endorsed by the 
ICH Steering Committee at Step 4 of the ICH process, October 27, 1994.  At Step 4 of the process, the final draft is 
recommended for adoption to the regulatory bodies of the ICH regions. This guidance is applicable to drug and 
biological products. 
  1  Contains Nonbinding Recommendations 
 
II.  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 substance, 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 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  
o
  Intermediate Precision 
o
  Specificity  
  2  Contains Nonbinding Recommendations 
 
  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 changes.  Certain other changes 
may require validation as well. 
   
  3  Contains Nonbinding Recommendations 
 
TABLE 
 
TYPE OF ANALYTICAL  IDENTIFICATION  TESTING FOR IMPURITIES  ASSAY; dissolution 
PROCEDURE;  (measurement only); 
CHARACTERISTICS  content/potency 
     
  Quantitation  Limit 
Accuracy  -  +  -  + 
       
Precision 
Repeatability  -  +  -  + 
Interm. Precision  -       + 1  -  +1 
Specificity2   +  +  +  + 
Detection Limit  -  - 3  +  - 
Quantitation Limit  -  +  -  - 
Linearity  -  +  -  + 
Range  -  +  -  + 
 
NOTE: - 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 
 
   
  4  Contains Nonbinding Recommendations 
 
APPENDIX A.  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. 
  5  Contains Nonbinding Recommendations 
 
 
a.  Repeatability 
 
Repeatability expresses the precision under the same operating conditions over a short 
interval of time. Repeatability is also termed intra-assay precision. 
 
b.  Intermediate precision 
 
Intermediate precision expresses within-laboratories variations: different days, different 
analysts, different equipment, etc. 
 
c.  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. 
  6  Contains Nonbinding Recommendations 
 
 
PART II6  
 
VALIDATION OF ANALYTICAL PROCEDURES: METHODOLOGY 
 
I.  INTRODUCTION  
 
This document is complementary to the parent document, which presents a discussion of the 
characteristics that should be considered during the validation of analytical procedures. Its 
purpose is to provide some guidance and recommendations on how to consider the various 
validation characteristics for each analytical procedure. In some cases (for example, 
demonstration of specificity), the overall capabilities of a number of analytical procedures in 
combination may be investigated in order to ensure the quality of the drug substance or drug 
product. In addition, the document provides an indication of the data that should be presented in 
a new drug application.  
 
All relevant data collected during validation and formulae used for calculating validation 
characteristics should be submitted and discussed as appropriate.  
 
Approaches other than those set forth in this guidance may be applicable and acceptable. It is the 
responsibility of the applicant to choose the validation procedure and protocol most suitable for 
their product. However, it is important to remember that the main objective of validation of an 
analytical procedure is to demonstrate that the procedure is suitable for its intended purpose. Due 
to their complex nature, analytical procedures for biological and biotechnological products in 
some cases may be approached differently than in this document.  
 
Well-characterized reference materials, with documented purity, should be used throughout the 
validation study. The degree of purity necessary depends on the intended use.  
 
In accordance with the parent document, and for the sake of clarity, this document considers the 
various validation characteristics in distinct sections. The arrangement of these sections reflects 
the process by which an analytical procedure may be developed and evaluated. 
 
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, overall 
knowledge of the capabilities of the analytical procedure, for instance: Specificity, linearity, 
range, accuracy, and precision. 
 
 
 
6 Part II of this guidance was developed within the Expert Working Group (Quality) of the International Council for 
Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) and has been subject to 
consultation by the regulatory parties, in accordance with the ICH process.  This document has been endorsed by the 
ICH Steering Committee at Step 4 of the ICH process, November 1996.  At Step 4 of the process, the final draft is 
recommended for adoption to the regulatory bodies of the ICH regions. This guidance is applicable to drug and 
biological products. 
  7  Contains Nonbinding Recommendations 
 
II.   SPECIFICITY (1)  
 
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.  
 
A. Identification (1.1)  
 
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 sensible scientific judgment with a 
consideration of the interferences that could occur.  
 
B. Assay and Impurity Test(s) (1.2)  
 
For chromatographic procedures, representative chromatograms should be used to demonstrate 
specificity, and individual components should be appropriately labeled. 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 nonspecific 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:  
 
1. Impurities are available (1.2.1)  
 
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 
  2  Contains Nonbinding Recommendations 
 
levels of impurities and demonstrating the separation of these impurities individually and/or from 
other components in the sample matrix.  
 
2. Impurities are not available (1.2.2)  
 
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). 
 
 
III.  LINEARITY (2)  
 
A linear relationship should be evaluated across the range (see section 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 have 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 five concentrations is recommended. Other 
approaches should be justified.  
 
  3  Contains Nonbinding Recommendations 
 
 
IV.  RANGE (3) 
 
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 percent over the specified range; e.g., if the specifications 
for a controlled released product cover a region from 20 percent, after 1 hour, up to 90 
percent, after 24 hours, the validated range would be 0-110 percent of the label claim;  
 
  For the determination of an impurity:  From the reporting level of an impurity7 to 120 
percent 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 percent standard is 
used, linearity should cover the range from the reporting level of the impurities8 to 120 
percent of the assay specification. 
 
V.   ACCURACY (4)  
 
Accuracy should be established across the specified range of the analytical procedure.  
 
A. Assay (4.1)  
 
 
7 See sections on "Reporting Impurity Content of Batches" of the corresponding guidance ICH Q3A Impurities in 
New Drug Substances (January 1996) and ICH Q3B guidance Impurities in New Drug Products (May 1997). 
8 See footnote 7. 
  4  Contains Nonbinding Recommendations 
 
1. Drug substance (4.1.1)  
 
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 section 1.2.);  
 
(c) Accuracy may be inferred once precision, linearity, and specificity have been established.  
 
2. Drug product (4.1.2)  
 
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 analyzed 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 section 1.2);  
 
(c) Accuracy may be inferred once precision, linearity, and specificity have been established. 
 
B. Impurities (Quantitation) (4.2)  
 
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 section 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.  
 
C. Recommended Data (4.3)  
 
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).  
 
  5  Contains Nonbinding Recommendations 
 
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.   
 
 
VI.   PRECISION (5)  
 
Validation of tests for assay and for quantitative determination of impurities includes an 
investigation of precision.  
 
A. Repeatability (5.1)  
 
Repeatability should be assessed using:  
 
(1) A minimum of 9 determinations covering the specified range for the procedure (e.g., 3 
concentrations/3 replicates each); or  
 
(2) A minimum of 6 determinations at 100 percent of the test concentration. 
 
B. Intermediate Precision (5.2)  
 
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 necessary to study these effects individually. The 
use of an experimental design (matrix) is encouraged.  
 
C. Reproducibility (5.3)  
 
Reproducibility is assessed by means of an interlaboratory 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.  
 
D. Recommended Data (5.4)  
 
The standard deviation, relative standard deviation (coefficient of variation), and confidence 
interval should be reported for each type of precision investigated. 
 
 
VII.   DETECTION LIMIT (6)  
 
Several approaches for determining the detection limit are possible, depending on whether the 
procedure is noninstrumental or instrumental. Approaches other than those listed below may be 
acceptable.  
 
  6  Contains Nonbinding Recommendations 
 
A. Based on Visual Evaluation (6.1)  
 
Visual evaluation may be used for noninstrumental 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.  
 
B. Based on Signal-to-Noise (6.2)  
 
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. 
 
C. Based on the Standard Deviation of the Response and the Slope (6.3) 
 
The detection limit (DL) may be expressed as:  
 
 
  3.3
DDDD =
where  = the standard deviation of the response   SS
   S = the slope of the calibration curve  
 
The slope S may be estimated from the calibration curve of the analyte. The estimate of  may be 
carried out in a variety of ways, for example: 
 
1. Based on the standard deviation of the blank (6.3.1)  
 
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.  
 
2. Based on the calibration curve (6.3.2)  
 
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. 
 
D. Recommended Data (6.4)  
 
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.  
 
  7  Contains Nonbinding Recommendations 
 
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. 
 
 
VIII.   QUANTITATION LIMIT (7)  
 
Several approaches for determining the quantitation limit are possible, depending on whether the 
procedure is noninstrumental or instrumental. Approaches other than those listed below may be 
acceptable. 
 
A. Based on Visual Evaluation (7.1)  
 
Visual evaluation may be used for noninstrumental 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.  
 
B. Based on Signal-to-Noise (7.2)  
 
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. 
 
C. Based on the Standard Deviation of the Response and the Slope (7.3)  
 
The quantitation limit (QL) may be expressed as:  
 
 
  10
QQDD = 
where  = the standard deviation of responses   SS
  S = the slope of the calibration curve  
 
The slope S may be estimated from the calibration curve of the analyte. The estimate of  may be 
carried out in a variety of ways, for example: 
 
1. Based on standard deviation of the blank (7.3.1)  
 
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.  
 
  8  Contains Nonbinding Recommendations 
 
2. Based on the calibration curve (7.3.2.)  
 
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. 
 
D. Recommended Data (7.4)  
 
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. 
 
 
IX.   ROBUSTNESS (8)  
 
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 
 
 
   
  9  Contains Nonbinding Recommendations 
 
X.   SYSTEM SUITABILITY TESTING (9)  
 
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. See 
pharmacopoeias for additional information. 
  10