The lines on a peptide certificate
| Line | What it records | What to check |
|---|---|---|
| Product name and sequence | Which peptide was tested | It matches your order, including any Ac- at the start or -NH₂ at the end |
| Salt form | The counter-ion, usually acetate or trifluoroacetate (TFA) | It matches what you asked for, if you asked |
| Batch or lot number | The production run the results belong to | The same number on vial, box, delivery note and certificate |
| Dates | Manufacture, testing, and retest or expiry | Testing follows manufacture, and your batch is within its date |
| Appearance | How the material looked, for example a white freeze-dried powder | Yours looks the same |
| Molecular formula and weight | Values calculated from the sequence | They fit the sequence; the peptide calculator checks them |
| Mass spectrometry (MS) | The measured mass | It matches the calculated mass for the ion stated |
| HPLC purity | The target peptide's share of the material the detector sees | The figure, the method, the wavelength, and ideally the chromatogram |
| Net peptide content | The share of the powder's weight that is peptide | Needed to know any real concentration |
| Water and counter-ion | What else is in the powder | Part of the mass balance below |
| Specification | The limit each result is judged against | Every result meets its limit |
| Storage | The recommended condition | It matches the label |
| Laboratory and release | Who tested and who approved the batch | A named laboratory and a named approver or signature |
A worked example
Bachem, a large peptide manufacturer, publishes an example for bradykinin acetate. Its figures are set out below as a certificate would show them, with the values that follow from the sequence. It is an illustration, not one of our batches.
| Line | Entry | What it tells you |
|---|---|---|
| Product | Bradykinin acetate | The peptide, and acetate as its counter-ion |
| Sequence | H-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg-OH (RPPGFSPFR) | Nine residues, with a free amino group at the start and a free acid at the end |
| Molecular formula | C₅₀H₇₃N₁₅O₁₁ | The peptide alone, without acetate or water |
| Molecular weight (average) | 1060.22 g/mol | The figure for weighing and molar calculations |
| Monoisotopic mass | 1059.56 Da | The figure a mass spectrometer looks for in a small peptide |
| Expected ions | [M+H]⁺ 1060.57; [M+2H]²⁺ 530.79 | The measured peak should match one of these within the instrument's tolerance |
| HPLC purity | 98.7% | 98.7% of the material absorbing at 220 nm is bradykinin |
| Net peptide content | 85.0% | 85.0% of the powder's weight is peptide; the rest is acetate and water |
Now combine the last two lines. By Bachem's own sum, 5 mg of this powder holds 4.195 mg of bradykinin, or 3.956 µmol. Made up to 10 mL, that is about 0.40 mmol/L, where the gross weight alone suggests 0.47 mmol/L: a difference of about 16%, found only by reading the certificate.
Identity: the mass spectrum
Mass spectrometry measures mass divided by charge. Two points cause most of the confusion.
Charge. A peptide carrying one extra proton appears at its mass plus about 1 (1.00728 Da); with two, at about half its mass plus 1. So bradykinin can show at 1060.57 or at 530.79, and a good certificate names the ion it reports.
Monoisotopic or average. Small peptides are usually reported by monoisotopic mass, larger ones by average mass. For bradykinin the two differ by 0.66 Da, so compare like with like. Amino acid codes gives both kinds of residue mass.
A correct mass shows that the molecule is present. It does not show how much else is there.
Purity: the chromatogram
HPLC separates the dissolved sample, and a UV detector draws each component as a peak. Bachem defines HPLC purity as the percentage of the requested peptide relative to all material absorbing at 220 nm. The small peaks are mostly near relatives of the target from synthesis, such as chains missing one amino acid.
A peak shows that something is there, not what it is. Two compounds can leave the column together under one peak. That is why HPLC and mass spectrometry together tell you far more than either alone. Peptide purity explained goes further.
Content: what the powder is made of
A freeze-dried peptide is a salt that holds some water, and net peptide content is the peptide share of its weight. GenScript gives a check that a full set of results should pass: target peptide + peptidic impurities + counter-ion + water = 100%. If all four are printed, add them up.
What a certificate does not tell you
- Sterility or endotoxin, unless a result is printed.
- How the material has been kept since testing. That depends on transport and on your own storage.
- Anything about use in people or animals. A certificate describes a batch of material. It does not make a research material suitable for a body.
Certificate of analysis, Certificate of Conformity, state testing
Three documents and checks in Iraq have similar names or purposes. Keep them apart.
- The certificate of analysis is the manufacturer's record of one batch, sometimes backed by a report from an independent laboratory.
- The Certificate of Conformity is issued under Iraq's Conformity Assessment Programme for each imported consignment of regulated products, which include chemicals and cosmetics. It is issued before shipment and concerns the consignment's conformity. It is not a batch analysis.
- State testing applies to medicines. The National Center for Drug Control and Research tests medicines for registration and usually examines each batch before release, by US, British or European pharmacopoeia methods where they exist. Research materials and cosmetic raw materials have no such step, so their certificate, and who issued it, carry the whole weight.
Whichever report you hold, check that it names the laboratory and carries a report number that laboratory can confirm.
Signs a certificate may not be genuine
- No batch number, or one that does not match the goods.
- The same certificate for every batch or every strength.
- Dates that do not fit: testing before manufacture, or a certificate years older than the goods.
- No named laboratory, or one that cannot be found.
- A measured mass that does not fit the sequence.
- Results that are too tidy: purity of exactly 100%, or identical figures batch after batch.
- A purity figure with no method, and no chromatogram when asked.
None of these proves a forgery on its own. Each is a reason to ask before you buy.
Our certificates
The manufacturer's certificate of analysis comes with every batch, and certificates of analysis explains how we keep them. Testing explains who tests what. We supply businesses and institutions in Iraq, not individuals.
Questions people ask
- What is a certificate of analysis?
A laboratory's record of test results for one batch: for a peptide, identity, purity and content, with the methods, limits, dates and the name of whoever released the batch.
- Is a certificate of analysis the same as a specification?
No. A specification sets the limits a product must meet. A certificate records the actual results for one batch against those limits.
- Is a Certificate of Conformity the same as a certificate of analysis?
No. The Certificate of Conformity is a consignment document under Iraq's import programme. The certificate of analysis records the tests on a batch.
- Can I ask for the chromatogram and the mass spectrum?
Yes. A supplier whose batches are properly tested can send both.