Analytical Specificity for Peptide Methods
Specificity is the ability to measure the intended analyte in the presence of expected interferences.
Potential interferences
- synthesis impurities
- degradation products
- excipients
- counterions
- solvents
- matrix components
- system peaks
- co-eluting analogs
Demonstrating specificity
Evidence may include:
- blank and placebo injections
- impurity spiking
- forced degradation
- orthogonal chromatography
- LC-MS
- spectral comparison
- peak-purity analysis
Identity versus quantitation
A method may be sufficiently specific for identity but not for low-level impurity quantitation.
Frequently asked questions
Does retention time prove specificity?
No.
Is diode-array peak purity enough?
It is supportive but not definitive.
Can specificity be sequence-specific?
Yes. Closely related analogs may require specialized separation.
Does a blank test every interference?
No. Process and degradation impurities must also be considered.
Key takeaways
Specificity is demonstrated against realistic interferences. It is the foundation for credible identity, assay, and impurity results.
References
- ICH Q2(R2). Validation of Analytical Procedures.
- ICH Q14. Analytical Procedure Development.
- FDA. Analytical Procedures and Methods Validation for Drugs and Biologics.
TSMS Labs educational disclaimer: For laboratory research and educational purposes only. Not for human consumption. This content is not medical, clinical, or regulatory advice.