How to read a certificate of analysis

Bachem, one of the large peptide manufacturers, publishes a worked example for bradykinin acetate. Below, its figures are laid out as they would appear on a certificate, with the values that follow from the sequence. It is an illustration, not one of our batches.

Put the last two lines together. Weigh out 5 mg of this powder and you have 5 × 0.850 × 0.987 = 4.195 mg of bradykinin, which is 3.956 µmol at 1060.22 g/mol. Dissolve it in 5 mL expecting 1 mg/mL, and the real concentration is about 0.84 mg/mL.

Mass spectrometry measures mass divided by charge, and two points confuse buyers.

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 the example molecule 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 proves the molecule is present. It says nothing about how much else is there.

HPLC separates the 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 smaller 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, and two compounds can leave the column together under one peak. The EDA's guide for synthetic peptide medicines asks for orthogonal methods, meaning methods based on different physical principles, for exactly that reason. A research certificate is not held to that standard, but the lesson carries over: HPLC and MS together tell you far more than either alone. Peptide purity explained goes further.

A freeze-dried peptide is a salt that holds some water, and net peptide content is the peptide fraction of it. GenScript gives a check a full certificate should pass: target peptide + peptide impurities + counter-ion + water = 100%. If all four figures are printed, add them up.

• Sterility or endotoxin, unless a result is printed.
• How the material has been kept since it was tested. 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.

Most certificates come from the manufacturer, which tests each batch before release. Some suppliers also send samples to an independent laboratory. For a registered medicine imported into Egypt, the EDA goes further: its guide holds the first shipment after registration until the EDA's Central Administration for Drug Control has issued its own analysis. Research materials and cosmetic raw materials have no such step, which is why the certificate, and who issued it, matter so much.

Whichever report you hold, check that it names the laboratory and carries a report number that laboratory can confirm.

1. No batch number, or one that does not match the goods.
2. One certificate used for every batch or every strength.
3. Dates that do not fit: a test before manufacture, or a certificate years older than the goods.
4. No named laboratory, or one that cannot be found.
5. A measured mass that does not match the sequence.
6. Results that are too neat: purity of exactly 100%, or identical figures across batches.
7. A purity figure with no method, and no chromatogram on request.

None of these proves a fake by itself. Each is a reason to ask before you buy.

The certificate for each batch travels with the delivery. How we test explains who tests what. We supply businesses and institutions in Egypt, not individuals.