1. Is there an independent certificate of analysis (COA) for this exact batch?
A certificate of analysis (COA) documents the identity, purity and composition of a specific product. The key word is specific: a good COA is tied to the exact batch (lot) you receive, not a generic template or a "representative" document for the peptide in general. Look for a lot number that matches the vial label, a test date, the analytical methods used, and — ideally — testing by an independent third-party laboratory rather than only the seller's own claim. Red flags: no COA at all; a COA with no lot number; a single COA reused across every batch; blurry or editable PDFs; or a result stated only as "≥99%" with no chromatogram or spectrum attached. Independent, batch-specific documentation is the single most informative signal of a serious supplier.
2. Is purity confirmed by HPLC and identity by mass spectrometry?
Two complementary analyses answer two different questions. High-performance liquid chromatography (HPLC) tells you how much of the material is the target compound — purity is the main peak area divided by the total area of all peaks. Mass spectrometry tells you what the compound actually is, by measuring its molecular mass, often to within a few parts per million (ppm). The two are not interchangeable: a peptide can read 99% pure by HPLC yet carry the wrong sequence, or show a correct mass while impurities hide under a single peak. A credible COA shows both, ideally with the actual chromatogram and spectrum. Research-grade material is typically expected at ≥95–98% purity by HPLC. Red flag: a purity figure with no method named, no chromatogram, and no mass confirmation.
3. Is the batch (lot) traceable?
Traceability means every vial can be linked back through a documented chain: lot number, synthesis or fill date, the analytical records for that lot, and the storage history. It is what lets you reproduce an experiment, compare results over time, and — if something looks off — determine which batch was involved. In falsified-medicine research, the batch number is one of the core elements used to verify authenticity, and its absence is treated as a warning sign. A good supplier prints a lot number on the vial that matches the COA and can retrieve records on request. Red flags: unlabelled vials, lot numbers that do not match the paperwork, or a shop that cannot tell you when and where a specific lot was made and tested.
4. Where and under what conditions is the product made and stored?
Peptides are chemically fragile. Published reviews document degradation via hydrolysis, deamidation, oxidation, β-elimination and aggregation, and note that these are accelerated by heat, moisture, oxygen and light. That makes production and handling conditions part of quality, not an afterthought. Formulation literature stresses controlled processing, oxygen exclusion, and a cold chain — lyophilised material kept frozen, with minimal temperature excursions. A serious supplier can describe where material is synthesised, how it is lyophilised and filled, and at what temperature it is stored and shipped. Red flags: no information on origin or storage, room-temperature shipping of material that should be cold, vials with moisture or discolouration, and vague answers about handling. Ask specifically how the product is stored and transported.
5. Is the price suspiciously low — and why?
Rigorous analytics — independent HPLC, mass spectrometry, per-batch documentation and cold-chain logistics — cost money. A price far below the market usually means one of those steps was skipped. Substandard and falsified products are, by definition, misrepresented on identity, composition or source, and an implausible price is a classic signal of that. Treat a bargain as a reason to check the COA harder, not as a win. And a critical distinction: a supplier that provides human dosing instructions, reconstitution-for-injection guidance, or "how to use it" protocols is showing a red flag, not offering a service. Research peptides are laboratory reagents; framing them for human use reveals a seller who ignores the regulatory line, and that same disregard tends to extend to quality control.
Closing: research use only and verified quality
All peptid.si products are supplied strictly for research use only (RUO) — they are laboratory reagents, not medicines, and are not intended for human or veterinary use, diagnosis or treatment. The five questions above are simply the checklist a careful researcher applies to any supplier. peptid.si is built around exactly these answers: laboratory-verified purity by HPLC, identity confirmation by mass spectrometry, and a public, batch-specific certificate of analysis for every lot — collected in the COA Vault, where you can review the documentation for the material you receive before you rely on it.
References / Links
- Lian Z, Wang N, Tian Y, Huang L (2021). Characterization of Synthetic Peptide Therapeutics Using Liquid Chromatography-Mass Spectrometry: Challenges, Solutions, Pitfalls, and Future Perspectives. Journal of the American Society for Mass Spectrometry. PubMed
- Zapadka KL, Becher FJ, Gomes dos Santos AL, Jackson SE (2017). Factors affecting the physical stability (aggregation) of peptide therapeutics. Interface Focus (Royal Society). PubMed
- Nugrahadi PP, Hinrichs WLJ, Frijlink HW, Schöneich C, Avanti C (2023). Designing Formulation Strategies for Enhanced Stability of Therapeutic Peptides in Aqueous Solutions: A Review. Pharmaceutics (MDPI). MDPI
- El-Dahiyat F, Fahelelbom KMS, Jairoun AA, Al-Hemyari SS (2021). Combatting Substandard and Falsified Medicines: Public Awareness and Identification of Counterfeit Medications. Frontiers in Public Health. Frontiers
