How to read a Certificate of Analysis, interpret the data, and spot a fake.
Product ID — Peptide name, sequence, CAS number. Batch/lot number — Must match product label. Dates — Manufacturing, testing, and expiry. HPLC purity — With method details (column, mobile phase, gradient). Mass spectrometry — Observed vs theoretical molecular weight. Endotoxin — LAL test (required for injectables). Residual solvents — Per ICH Q3C. Heavy metals — ICP-MS results. Water content — Karl Fischer titration.
HPLC separates the target peptide from synthesis byproducts and reports purity as a percentage of UV-absorbing peaks. “98.7% purity” means your peptide is 98.7% of the peptide-related material. But HPLC doesn’t capture water, counterion salts, or non-UV contaminants — so a peptide with 99% HPLC purity might only be 75–85% peptide by weight. Both numbers should appear on a complete COA.
Confirms identity by comparing observed molecular weight to theoretical. HPLC says “how pure” — mass spec says “what it is.” A COA with HPLC but no mass spec is incomplete. You might have a very pure wrong peptide.
Injectable peptides require LAL endotoxin testing, residual solvent analysis (GC), and heavy metal screening (ICP-MS). A “pharmaceutical grade” COA missing any of these isn’t pharmaceutical grade.
Generic templates — Identical results across batches. Real data has natural variation.
Round numbers — Real HPLC gives 98.73%, not exactly 99.0% every time.
No chromatograms — Or unlabeled decorative traces instead of real data with axis labels and integration values.
No lab identified — “Tested in-house” without details. Third-party testing is stronger.
Identical formatting across different peptides from supposedly different manufacturers.
Send a sample to an accredited lab (Intertek, Eurofins, SGS). Run HPLC + mass spec. Compare to the supplier’s COA. Cost: $200–500. Test every new supplier’s first batch, then spot-check periodically.