Reading a Certificate of Analysis: HPLC Purity, Mass Spec & Red Flags Explained

A Certificate of Analysis (COA) is a document issued by a testing laboratory stating the results of analytical testing performed on a specific batch of peptide. It is the primary quality document in peptide research — it tells you what’s in the vial, how pure it is, and whether the compound is what the vendor claims. A COA from a reputable independent lab, interpreted correctly, is the closest thing to assurance you can get about the product you’re using. A COA from an unvetted or in-house source may be meaningless or fabricated.

HPLC Purity: The Core Metric

High-performance liquid chromatography (HPLC) separates compounds in a sample by their chemical properties (polarity, charge, size) as they pass through a column under pressure. The result is a chromatogram showing peaks corresponding to compounds in the sample. The area under each peak is proportional to the quantity of that compound. Purity % = (area of target peptide peak / total peak area) × 100.

A purity of ≥98% by HPLC means the target peptide constitutes at least 98% of all UV-absorbing (at 220–254 nm) material in the sample. What the remaining 2% consists of is unknown without further testing — it could be unreacted amino acids, deletion sequences, oxidized variants, or residual solvent. For research purposes, ≥98% HPLC purity is the generally accepted minimum for injectable peptides. ≥99% is preferred.

Mass Spectrometry Confirmation

Mass spectrometry (MS) measures the mass-to-charge ratio of ions and can confirm the molecular weight of the peptide. A COA that reports both HPLC purity and MS confirmation provides two independent data points: purity (HPLC) and identity (MS). The reported observed mass should match the calculated theoretical molecular weight of the peptide. For example, BPC-157 has a theoretical MW of 1419.53 Da; an MS result of [M+H]+ = 1420.5 m/z confirms the correct peptide.

Note that MS confirms identity but not purity: a sample could be 50% pure and still show the correct molecular weight peak if the target peptide is present at all. This is why HPLC and MS together are stronger than either alone.

Peptide Content vs. Net Peptide: Water and Acetate

Lyophilized peptides absorb water and retain counterions from synthesis (commonly trifluoroacetate from HPLC purification, sometimes converted to acetate). A vial labeled “5 mg” contains 5 mg of crude material by weight — but the net peptide content (actual peptide mass excluding water and salt counterions) may be 80–95% of the labeled amount. Some vendors report net peptide content separately. A COA that quantifies water content (by Karl Fischer titration) and counterion content (by ion chromatography or NMR) provides a more accurate picture of actual peptide yield per vial.

Red Flags: Signs of a Fraudulent or Inadequate COA

Missing test methods: A legitimate COA identifies the specific analytical method used (e.g., “RP-HPLC, C18 column, 220 nm detection”). A COA that simply states “Purity: 98.5%” with no method citation cannot be verified or replicated. Unsigned COAs: Reputable labs issue COAs with a signature or stamp from the responsible analyst or QC manager. An unsigned, unsigned-format PDF should be treated with skepticism. Vendor name mismatch: The COA should name the testing lab, not just the peptide vendor. If a COA is printed on the vendor’s own letterhead without a third-party lab name, it is likely in-house testing — which is a conflict of interest.

Wrong compound name: Occasionally a vendor uses a COA from one compound for a different compound (fraud). Check that the peptide name on the COA matches the peptide you ordered, including the specific sequence variant (e.g., BPC-157 is a specific sequence — not any “gastric pentadecapeptide”). Expired COA: COAs are issued for specific lots; a COA dated 2–3 years ago for a compound you’re receiving today may represent an entirely different production batch. A COA should match the current lot number on the vial. No lot number: If neither the vial nor the COA carries a lot number, there is no audit trail.

Trusted Labs: What to Look For

Janoshik Analytical (janoshik.com), Analytical Forensic Intelligence (AFI), and Chromate Scientific are among the most frequently referenced independent testing labs in the peptide research community. These labs accept direct submissions from individuals, publish results under verifiable order numbers, and have established track records. Testing services from labs with ISO/IEC 17025 accreditation (the international standard for testing laboratories) provide the highest level of methodological assurance. When evaluating a vendor, check if their COAs link to verifiable lab order numbers that can be independently confirmed on the lab’s website.

Pepticker’s methodology and resources pages at /methodology explain our vendor COA verification standards in detail. We cross-reference vendor-provided COAs with independently submitted lab tests where available, and flag discrepancies in our vendor news at /vendornews.