COA Transparency Is Non-Negotiable
The single most important factor when evaluating a peptide supplier is their Certificate of Analysis practices. A trustworthy supplier publishes COAs for every batch — not generic documents, but batch-specific reports with unique lot numbers that match the product you receive.
Red flags include: COAs that are only available "upon request," documents without batch/lot numbers, COAs showing suspiciously identical results across different batches, and reports from unnamed or unverifiable laboratories.
HPLC Data Quality
Look for suppliers who publish actual HPLC chromatograms — the graph, not just a purity number. A chromatogram lets you verify that there is indeed a single dominant peak and assess the baseline for noise or impurity peaks. A purity percentage without a chromatogram is just a claim.
The chromatogram should show: clear peak separation, stable baseline, retention time consistent with the target peptide, and peak area percentages for any detected impurities.
Mass Spectrometry Data
A supplier providing both HPLC (purity) and MS (identity) data demonstrates a higher standard of quality verification. HPLC alone can confirm purity but not identity — a vial could be 99% pure of the wrong peptide. Mass spectrometry confirms molecular identity.
Pricing Red Flags
If a supplier's prices are dramatically lower than the market average, investigate why. Peptide synthesis has real costs — amino acid reagents, HPLC purification, quality testing, lyophilization, and proper packaging. Prices far below competitors may indicate reduced purification (lower purity), skipped testing, or lower actual quantities than labeled.
Conversely, the most expensive supplier is not automatically the best. Compare the combination of price, published quality data, and batch-specific documentation.
Shipping and Storage
Peptides are sensitive to heat. A quality supplier ships with appropriate packaging — insulated containers and cold packs during warm months. They also clearly label storage requirements on the product and provide guidance on reconstitution and handling.
Customer Support
Can you contact the supplier with technical questions? A legitimate research supplier should be able to discuss peptide purity, storage recommendations, reconstitution protocols, and COA interpretation. If a supplier cannot or will not answer basic technical questions, this is a significant concern.
Website and Documentation
Look for: clear product descriptions with amino acid sequences, published COAs accessible without creating an account, a physical business address, contact information, and clear terms of service specifying research-use-only.
