ICH Q2(R1) Guideline on Validation of Analytical Procedures PDF

INTERNATIONAL CONFERENCE ON HARMONISATION OF TECHNICAL REQUIREMENTS FOR REGISTRATION OF PHARMACEUTICALS FOR HUMAN USE ICH HARMONISED TRIPARTITE GUIDELINE VALIDATION OF ANALYTICAL PROCEDURES: TEXT AND METHODOLOGY...

INTERNATIONAL CONFERENCE ON HARMONISATION OF TECHNICAL REQUIREMENTS FOR REGISTRATION OF PHARMACEUTICALS FOR HUMAN USE ICH HARMONISED TRIPARTITE GUIDELINE VALIDATION OF ANALYTICAL PROCEDURES: TEXT AND METHODOLOGY Q2(R1) Current Step 4 version Parent Guideline dated 27 October 1994 (Complementary Guideline on Methodology dated 6 November 1996 incorporated in November 2005) This Guideline has been developed by the appropriate ICH Expert Working Group and has been subject to consultation by the regulatory parties, in accordance with the ICH Process. At Step 4 of the Process the final draft is recommended for adoption to the regulatory bodies of the European Union, Japan and USA.  Q2(R1) Document History New First Codification History Date Codification November 2005 Parent Guideline: Text on Validation of Analytical Procedures Q2 Approval by the Steering Committee under Step 2 and 26 Q2 release for public consultation. October 1993 Q2A Approval by the Steering Committee under Step 4 and 27 Q2 recommendation for adoption to the three ICH October regulatory bodies. 1994 Guideline on Validation of Analytical Procedures: Methodology developed to complement the Parent Guideline Q2B Approval by the Steering Committee under Step 2 and 29 in Q2(R1) release for public consultation. November 1995 Q2B Approval by the Steering Committee under Step 4 and 6 in Q2(R1) recommendation for adoption to the three ICH November regulatory bodies. 1996 Current Step 4 version Q2A and The parent guideline is now renamed Q2(R1) as the November Q2(R1) Q2B guideline Q2B on methology has been incorporated to 2005 the parent guideline. The new title is “Validation of Analytical Procedures: Text and Methodology”.  VALIDATION OF ANALYTICAL PROCEDURES: TEXT AND METHODOLOGY ICH Harmonised Tripartite Guideline TABLE OF CONTENTS PART I: TEXT ON VALIDATION OF ANALYTICAL PROCEDURES................................ 1 1. Introduction......................................................................................................... 1 2. Types of Analytical Procedures to be Validated................................................. 1 TABLE......................................................................................................................... 3 GLOSSARY.................................................................................................................... 4 PART II: VALIDATION OF ANALYTICAL PROCEDURES: METHODOLOGY................. 6 INTRODUCTION.......................................................................................................... 6 1. SPECIFICITY...................................................................................................... 6 1.1. Identification.................................................................................................... 7 1.2. Assay and Impurity Test(s)............................................................................. 7 2. LINEARITY.......................................................................................................... 8 3. RANGE................................................................................................................. 8 4. ACCURACY.......................................................................................................... 9 4.1. Assay................................................................................................................ 9 4.2. Impurities (Quantitation)...............................................................................10 4.3. Recommended Data........................................................................................10 5. PRECISION....................................................................................................... 10 5.1. Repeatability...................................................................................................10 5.2. Intermediate Precision...................................................................................10 5.3. Reproducibility................................................................................................10 5.4. Recommended Data........................................................................................10 6. DETECTION LIMIT......................................................................................... 11 6.1. Based on Visual Evaluation...........................................................................11 6.2. Based on Signal-to-Noise................................................................................11 6.3 Based on the Standard Deviation of the Response and the Slope................11 6.4 Recommended Data........................................................................................11 i Validation of Analytical Procedures: Text and Methodology 7. QUANTITATION LIMIT................................................................................... 12 7.1. Based on Visual Evaluation........................................................................... 12 7.2. Based on Signal-to-Noise Approach............................................................... 12 7.3. Based on the Standard Deviation of the Response and the Slope................ 12 7.4 Recommended Data........................................................................................ 13 8. ROBUSTNESS................................................................................................... 13 9. SYSTEM SUITABILITY TESTING................................................................. 13 ii  PART I: TEXT ON VALIDATION OF ANALYTICAL PROCEDURES ICH Harmonised Tripartite Guideline Having reached Step 4 of the ICH Process at the ICH Steering Committee meeting on 27 October 1994, this guideline is recommended for adoption to the three regulatory parties to ICH 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 EC, 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 EC, 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 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; 1 Validation of Analytical Procedures: Text - 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 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 changes. Certain other changes may require validation as well. 2  Validation of Analytical Procedures: Text TABLE Type of analytical IDENTIFICATION TESTING FOR ASSAY procedure IMPURITIES - dissolution (measurement only) - content/potency characteristics quantitat. limit Accuracy - + - + Precision Repeatability - + - + Interm.Precision - + (1) - + (1) Specificity (2) + + + + Detection Limit - - (3) + - Quantitation Limit - + - - Linearity - + - + Range - + - + - 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 Validation of Analytical Procedures: Text 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  Validation of Analytical Procedures: Text 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. 5  PART II: VALIDATION OF ANALYTICAL PROCEDURES: METHODOLOGY ICH Harmonised Tripartite Guideline Having reached Step 4 of the ICH Process at the ICH Steering Committee meeting on 6 November 1996, and incorporated into the core guideline in November 2005, this guideline is recommended for adoption to the three regulatory parties to ICH 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 which should be presented in a registration 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 guideline 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. 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 6  Validation of Analytical Procedures: Methodology more analytical procedures is recommended to achieve the necessary level of discrimination. 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. 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: 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. 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; 7 Validation of Analytical Procedures: Methodology - 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). 2. LINEARITY 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 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. 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. 8  Validation of Analytical Procedures: Methodology - for the determination of an impurity: from the reporting level of an impurity1 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 impurities1 to 120% of the assay specification. 4. ACCURACY Accuracy should be established across the specified range of the analytical procedure. 4.1. Assay 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 1.2.); c) accuracy may be inferred once precision, linearity and specificity have been established. 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 1.2.); c) accuracy may be inferred once precision, linearity and specificity have been established. 1 see chapters “Reporting Impurity Content of Batches” of the corresponding ICH-Guidelines: “Impurities in New Drug Substances” and “Impurities in New Drug Products” 9 Validation of Analytical Procedures: Methodology 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 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. 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. 5. PRECISION Validation of tests for assay and for quantitative determination of impurities includes an investigation of precision. 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. 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. 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. 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. 10  Validation of Analytical Procedures: Methodology 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. 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. 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. 6.3 Based on the Standard Deviation of the Response and the Slope The detection limit (DL) may be expressed as: 3.3 σ DL = 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 σ may be carried out in a variety of ways, for example: 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. 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. 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. 11 Validation of Analytical Procedures: Methodology 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. 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. 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. 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. 7.3. Based on the Standard Deviation of the Response and the Slope The quantitation limit (QL) may be expressed as: 10 σ QL = 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 σ may be carried out in a variety of ways for example: 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. 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. 12  Validation of Analytical Procedures: Methodology 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. 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. 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. See Pharmacopoeias for additional information. 13