Method Validation
Definition
The documented exercise proving a method does what it claims: specificity, linearity, accuracy, precision, range, and the limits at which it stops working. Validation is done once for the method, not once per sample.
In more detail
Validation is the documented exercise that establishes a method does what it claims before it is used on real material: that it measures the intended analyte and not its neighbours, that the response is linear across the range of interest, that it is accurate and precise, and where it stops working at the bottom.
It is done once for the method rather than once per sample, which is the source of a common misreading. A certificate saying a validated method was used is saying the procedure was proven in general, not that this particular run behaved. System suitability is the check that covers the run.
What this means for research sourcing
Purity and identity verification are central to research reproducibility. Every Volta compound ships with >99% HPLC-verified purity and a certificate of analysis.
Related Terms in Quality
Method Verification
Demonstrating that an already-validated method performs as expected in the laboratory now using it. A compendial method arrives validated; a laboratory still has to show its own instruments and analysts reproduce it.
System Suitability
Checks run immediately before samples to prove the instrument is fit to measure anything that day: peak shape, resolution between critical pairs, and repeatability of replicate injections. A failed system suitability invalidates the run rather than the material.
Analytical Selectivity
A method's ability to measure the intended analyte without interference from impurities, excipients or degradation products. A purity figure from a method that cannot separate a close-eluting impurity overstates purity.
Orthogonal Method
A second method resting on a different physical principle, used to test a result rather than repeat it. Running reversed-phase HPLC and then mass spectrometry is orthogonal; running the same HPLC method twice is not.
Out of Specification (OOS)
A result that falls outside an acceptance criterion. It triggers an investigation into whether the measurement or the material is at fault, and an OOS cannot be resolved by simply retesting until a passing number appears.
Measurement Uncertainty
The range within which the true value is expected to lie, reported alongside the result. A purity of 99.2% with an uncertainty of 0.4% is not distinguishable from one of 99.5% measured the same way.
Metrological Traceability
An unbroken chain of comparisons linking a result back to a recognised reference, each step with its own stated uncertainty. It is what allows two laboratories using different instruments to be talking about the same milligram.
Measurand
The quantity actually being determined, stated precisely enough to be unambiguous. Peptide content, net peptide content and chromatographic purity are three different measurands on one vial, and they return three different numbers.