Analytical Counterfeit Detection

Analytical counterfeit detection is the set of laboratory tests applied to a finished product to answer four separate questions: is the molecule the one named, is it the dominant species present, how much of it is in the container, and what else came along. Each needs its own method. Mass spectrometry establishes that a species of the correct mass is present; chromatography, what fraction of the ultraviolet-absorbing material is the main peak; amino acid analysis after hydrolysis, how many milligrams of peptide the vial actually held. Endotoxin and microbial assays cover what no chemical method sees.

Real cases show why the panel has to be orthogonal. Regulators have warned about compounded products prepared from semaglutide salt forms rather than the base peptide, a substitution invisible to a purity percentage and obvious to a counterion assay. Counterfeit pens intercepted in legitimate distribution have been found to contain a different drug entirely, which only an identity test would catch. Independent testing of grey-market research vials repeatedly finds correct identity alongside content far below the labelled figure.

The value of the panel is that its results constrain each other. A correct mass with low net peptide content points at excess salt and water rather than a fake; a correct mass with a poor chromatogram points at synthesis impurities; a wrong mass ends the enquiry. Any single test taken alone leaves the largest failure modes uncovered.

The error that recurs is treating the seller's own certificate as the detection step, when that certificate is precisely the claim under test. A second is over-reading a clean mass spectrum: it excludes a wrong molecule but not a co-eluting deletion sequence, an epimer of identical formula, or a vial that is mostly trifluoroacetate. And chemical verification says nothing about sterility or pyrogenicity.