Reading a certificate of analysis
The certificate of analysis is the only hard evidence you have about a peptide. But only if you know what you are looking at, because a nice figure without context says little.
What belongs on it
- The name of the substance and the full amino acid sequence.
- The lot number, which must match the number on your vial.
- The date of analysis.
- An HPLC result with the purity figure and preferably the chromatogram itself.
- An MS result: the measured molecular weight next to the calculated weight.
- Appearance and net content.
If the lot number is missing, or differs from the one on your vial, you do not have a certificate for your product but a sample one. That is the difference between evidence and marketing.
What 99% actually means
The purity figure from an HPLC run is the area of your substance peak divided by the area of all peaks together. So it says: of everything the column saw, 99 percent was this one molecule.
That is exactly where it stops. The figure says nothing about substances the detector does not see, and nothing about how much of the vial is peptide. A freeze dried powder almost always contains salt and residual moisture as well. A vial can be 99 percent pure and still be part salt.
Purity is the ratio between your substance and other substances present. Content is how many milligrams of peptide are actually in the vial. The second question is rarely answered and is, for any calculation, the more important one.
Why MS has to be there
HPLC counts peaks but does not know what is in them. A substance that separates neatly and gives a fine narrow peak could be something quite different from what the label says. Mass spectrometry weighs the molecule and compares that with the weight belonging to the stated sequence.
If that weight does not match, the substance does not match, however high the HPLC figure. A certificate without MS leaves that question open.
What a chromatogram looks like
A chromatogram is a graph with time on the horizontal axis and signal on the vertical. Your substance appears as a peak. What you want to see is a tall, narrow, symmetrical peak with a flat line around it.
Watch for a peak with a shoulder on one side: that points to a second substance leaving the column at almost the same moment, often a chain missing one amino acid. Watch too for a run of small peaks just before the main one; those are usually degradation products.
Mixtures follow different rules
Blends, thymalin and cerebrolysin consist of several substances. A single purity figure is meaningless there: 99 percent of what? What you want to see for such a product is that each component was measured separately and that the ratio between components was established.
If a blend comes with a certificate carrying a single number, that is not an analysis of the product but at best of one of its ingredients.
What you can check yourself
- Does the lot number on the certificate match the vial?
- Is there both an HPLC and an MS result?
- Is the measured weight shown next to the calculated weight, and are they close?
- Is the chromatogram included, or only a number?
- Is the analysis date recent enough relative to the production date?
This site is made by the team behind Apex Bio Research, a Dutch supplier of research peptides with a certificate of analysis per batch.
Visit the shopThis site explains what the scientific literature says about peptides. It is not medical advice and not a set of instructions. The substances discussed here are research compounds: they are not approved for use in humans or animals. If you have a health question, see a doctor.
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