What Is a Certificate of Analysis?

A Certificate of Analysis (COA) is a quality assurance document issued by a laboratory that has tested a batch of chemical or biological material. For research peptides, a COA records the results of purity testing (HPLC), identity confirmation (mass spectrometry), and any additional tests performed. It should reference a specific production batch, not a generic product-level certificate, and be issued by an accredited third-party laboratory independent of the manufacturer. A COA that appears to be self-issued by the supplier, references no external laboratory, or lacks a batch number is not a reliable quality document.

Key Fields to Verify

When reviewing a peptide COA, check the following fields in order: (1) Product name, confirm it matches your order including format (e.g. "BPC-157 Acetate" not just "BPC-157"). (2) CAS number, should match the registered CAS for the compound. (3) Batch/lot number, write this down and verify it matches the label on your vial. (4) HPLC purity, should be ≥99% for Stackpure products; values below 95% are inadequate for most research purposes. (5) Observed molecular weight (MS), compare to the theoretical MW listed; should match within ±0.5 Da for ESI-TOF instruments. (6) Testing laboratory name, verify the laboratory is named (e.g. "Tested by XYZ Analytical, ISO 17025 accredited") and not "Tested in-house". (7) Test date, should reflect the batch manufacture date, not a multi-year-old certificate reused across batches.

HPLC Chromatogram Interpretation

A properly prepared COA includes the HPLC chromatogram image alongside the purity percentage. The chromatogram should show a dominant single peak at the expected retention time with the reported purity area. Small secondary peaks ≤1% of total area are acceptable and expected (deletion sequences, oxidised variants). Red flags include: multiple peaks of similar height (indicating a mixture or failed synthesis); a broad, asymmetric main peak (indicating aggregation or poor column resolution); or a chromatogram image that appears too clean (single perfect peak with no minor impurities, potentially fabricated). Retention time should be consistent across batches of the same peptide under the same conditions.

Mass Spectrum Verification

The MS section of a COA should state the theoretical molecular weight (calculated from sequence), the observed molecular weight (measured by MS), and the m/z values of the major ions detected. For ESI-MS of peptides, you will typically see multiply charged species: [M+2H]2+, [M+3H]3+, etc. Each ion gives an m/z reading; multiply by the charge state z and subtract z hydrogens to get the neutral molecular weight. For example: if [M+2H]2+ is observed at m/z 710.5, the neutral MW = (710.5 × 2) − (2 × 1.008) ≈ 1419 Da. This should match the theoretical MW within ±0.5 Da for a correctly synthesised peptide.

Requesting a COA from Stackpure

COAs are available for every Stackpure batch on request. To obtain yours: email sales@stackpure.is with (1) your order number and (2) the batch number printed on your product label (typically in the format SP-XXXXXX or stamped on the vial cap). COAs are returned within 24 hours on business days. If your vial is missing a batch number label, photograph the vial and include the order number in your email, our quality team can identify the batch from order records.