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By Dr. Pramod Kr. Pandey - May 2, 2025

Dr. Pramod Kr. Pandey is a distinguished Analytical Research Expert with over three decades of extensive experience in the pharmaceutical industry. He has contributed his expertise to both leading Indian and global pharmaceutical companies, consistently driving innovation and excellence in analytical research

Learn how to evaluate specificity during analytical method validation in pharmaceutical analysis. Includes step-by-step procedures, acceptance criteria, case study, and FAQs.

How To Perform Specificity In Analytical Method Validation: Get Mastery Easily

Specificity In Analytical Method Validation tells about the the efficiency of the analytical method or in other words capability of the method to separate different components like main analyte peak and impurity peaks.

Specificity is a critical parameter in the validation of analytical methods, particularly in pharmaceutical analysis. It ensures that the method can accurately measure the analyte of interest in the presence of potential interference such as impurities, degradation products, matrix components, or excitements. In this article, we will walk through the complete procedure for evaluating specificity, including sample and standard preparation, injection procedures, acceptance criteria, and a real-world case study. Additionally, we’ll cover frequently asked questions to help you address common challenges. By the end of this post, you will be equipped to confidently apply these steps during method validation or development.

Specificity in Analytical Method Validation

Specificity tells about the the efficiency of the analytical method or in other words capability of the method to separate different components like main analyte peak and impurity peaks.

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Procedure: Specificity in Analytical Method Validation

Standard and sample preparation

  1. Sample and standard solution: Prepare sample and standard at nominal concentration as per standard test procedure (STP).
  2. Known specified impurity solution: Prepare each known impurity at the specification level
  3. Known unspecified impurity solution: Prepare unknown specified impurity at 0.10% level
  4. Spiked solution preparation: Prepare a solution containing the main analyte at the nominal concentration and each known specified impurity at specification limit and known unspecified impurity at 0.10%.

Injection procedure

Inject the following solutions in the HPLC system containing a PDA or DAD detector and generate the chromatogram as per chromatographic condition given in the method::

  • Inject blank or diluent solution
  • Inject each known specified impurity
  • Inject each known unspecified impurity
  • Inject main analyte sample standard solution
  • Inject spiked solution
Specificity In Analytical Method Validation
Spiked sample and Blank chromatogram

Acceptance Criteria: Specificity in Analytical Method Validation

  • There should not be any interference of any known specified impurity with the main analyte
  • There should not be any interference of any known unspecified impurity with the main analyte
  • There should not be any interference of blank peak with the main analyte
  • There should not be any interference between known specified impurities and each peak should be separated
  • There should not be any interference between known unspecified impurities and each peak should be separated
  • There should not be any interference between known specified impurities and known unspecified impurity each peak should be separated
  • Each peak should be homogeneous and pure. For example, peak purity should be less than peak threshold

Case study

Let us consider the following are the related substances specification of an API and we have to perform specificity test:

  • Impurity A: NMT 0.50%
  • Impurity B: NMT 0,20%
  • Any known unspecified impurity NMT: 0.10%
  • Any unknown unspecified impurity NMT: 0.10%
  • Total impurity NMT: 1.0%

The sample concentration in the method is 1000 mcg/ml

Standard and sample preparation

  1. Prepare Impurity A at concentration, 1000 x 0.5/100=5 mcg/ml inject
  2. Prepare Impurity B at concentration, 1000 x 0.2/100=2 mcg/ml inject
  3. Prepare each known unspecified impurity at concentration, 1000 x 0.1/100=1 mcg/ml inject
  4. Spiked solution preparation: Prepare a solution containing the main analyte at the 1000 mcg/ml concentration and Impurity A at a concentration 5 mcg/ml, Impurity B at concentration 2 mcg/ml and each known unspecified impurity at concentration 1 mcg/ml and inject

Acceptance criteria

  • Impurity A must be separated with main peak amd Impurity B and any known or unknown unspecified
  • Impurity B must be separated with main peak amd Impurity A and any known or unknown unspecified
  • There should not be any interference blank peak with main analyte and with impurity A and Impurity B
  • Peak must be pure and homogeneous. Peak purity should be less than peak threshold

Specificity in stability indicating method (SIM) validation

In Stability indicating method validation sample is exposed to the following stress conditions to perform the specificity test:

  • Heat
  • Sun light or Sun cabinet
  • Basic treatment
  • Acidic treatment
  • Oxidation treatment

Difference between Specificity and Selectivity in Method Validation

SpecificitySelectivity
Specificity deals with the separation of peak of interest with the adjacent component peak or impurity peakSelectivity deals with the separation between each components in the chromatogram
In specificity, there should not be any interference of any peak with the peak of interestIn selectivity, there should not be any interference between each component
In the assay method, there should not be any interference of impurity peak with main peak. There may be interference between the impurities peaksIn the Related substances method, there should not be any interference between impurities peak and between main peak and impurity peak

Related Topic: What Is Analytical Method Validation In Pharmaceutical Analysis: Learn In 11 Minutes

Conclusion

Specificity is a fundamental aspect of analytical method validation, ensuring that the method can accurately measure the target analyte without interference from other components. By following the outlined procedures for sample and standard preparation, injection, and evaluation against defined acceptance criteria, analysts can confidently establish the reliability of their methods. Incorporating specificity studies during both method development and validation not only supports regulatory compliance but also enhances the overall robustness and accuracy of pharmaceutical analysis.

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FAQs

What is the specificity of method validation?

Specificity tells about the efficiency of the method to separate peak of interest from the adjacent component peak. Secondly, there should not be any interference of diluent peak with the peak of interest

What are the differences between selectivity and specificity?

Specificity deals with the separation of the peak of interest from the adjacent component peak or impurity peak. Selectivity deals with the separation between each component in the chromatogram.
For example assay method is specific whereas the related substance method is selective

What is the specificity of an assay?

There should not be any interference of the main peak or assay peak with any impurity peak or diluent peak.

What is specificity used for?

The peak of interest must be separated from other component peaks or diluent peak

What is specificity and sensitivity?

Specificity tells about the efficiency of the method to separate peak of interest from the adjacent component. There should not be any interference of diluent peak with the peak of interest. Sensitivity tells about the capacity of detector to quantify lowest amount of analytes. For sensitivity, the ratio of signal to noise (S/N) should be more than or equal to 10

Is specificity same as accuracy?

No. Specificity is related to the separation of the main component from the other component peaks whereas accuracy is related exactness of the method to quantify the analyte

References

Abbreviations

  • PDA: Photodiode array detector
  • DAD: Diode array detector
  • API: Active pharmaceutical ingredient
  • SIM: Stability indicating method

About Dr Pramod Kumar Pandey
Dr. Pramod Kr. Pandey

Dr. Pramod Kr. Pandey is a distinguished Analytical Research Expert with over three decades of extensive experience in the pharmaceutical industry. He has contributed his expertise to both leading Indian and global pharmaceutical companies, consistently driving innovation and excellence in analytical research

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