HPLC vs mass spec: what each COA test shows

A certificate of analysis for a research peptide usually reports two numbers that look alike and mean very different things: a purity percentage and a measured mass. They come from two instruments, and each one answers a question the other can't.

HPLC answers: how much of this is the peptide?

High-performance liquid chromatography pushes a dissolved sample through a packed column. Different molecules travel through it at different speeds, so they leave the column at different times. A detector at the end draws a line, the chromatogram, with a peak for every substance it sees.

Purity is the area under the main peak divided by the area under all the peaks. A lot reported at 99.1% means 99.1% of what the detector registered left the column at the time the target peptide does.

What HPLC can't tell you on its own is what that main peak is. A different peptide with similar chemistry could leave the column at nearly the same time.

Mass spectrometry answers: is it the right molecule?

A mass spectrometer turns molecules into charged particles and measures how heavy they are. Every peptide's sequence predicts an exact mass: BPC-157, fifteen amino acids long, should weigh about 1,419.5 daltons.

If the measured mass matches the predicted one within a fraction of a dalton, the lab has confirmed identity. If it doesn't, the vial holds something else, however clean its HPLC trace looks.

Why a good certificate shows both

• Purity without identity can describe a very pure sample of the wrong compound.
• Identity without purity can confirm the right molecule is present without saying how much else is there.
• Both, for the same lot, tell you what the powder is and how much of it is that thing.

What to check on the page

1. The lot number on the certificate matches the lot number on your label.
2. The test date is after the manufacture date.
3. The lab is named, and is not the seller.
4. The mass found is within about one dalton of the mass expected.
5. The purity is reported with its method (HPLC, with the detection wavelength).

Every certificate we publish shows these fields. You can look any lot up on the certificates page.

Not medical or veterinary advice. For informational purposes only. Products we sell are for research use only and are not for human consumption.