HPLC vs Mass Spectrometry: How Research Peptides Are Tested
When a supplier says a peptide is "third party tested," the two methods behind that claim are almost always HPLC and mass spectrometry. They are complementary. One measures purity, the other confirms identity.
HPLC: how pure is it?
High performance liquid chromatography pushes a dissolved sample through a packed column under high pressure. Different molecules travel through the column at different speeds, so they exit at different times. A detector records each one as a peak.
- The target peptide appears as the main peak.
- Impurities such as truncated sequences, deletion sequences, or leftover protecting groups appear as smaller peaks.
- Purity is calculated as the main peak area divided by the total peak area.
HPLC is excellent at telling you how clean a sample is. What it cannot tell you on its own is whether that main peak is the correct molecule.
Mass spectrometry: is it the right molecule?
Mass spectrometry ionizes the sample and measures the mass to charge ratio of the resulting ions. From that, the instrument determines the molecular weight. Every peptide sequence has a predictable theoretical mass, so if the observed mass matches, the identity is confirmed.
Why you need both
| Question | HPLC | Mass spec |
|---|---|---|
| How pure is the sample? | Yes | Limited |
| Is it the correct sequence? | No | Yes |
| Detects related impurities? | Yes | Partially |
A sample that passes HPLC but skips mass spec could be a very pure version of the wrong compound. A sample that passes mass spec but skips HPLC could be the right compound mixed with a large share of impurities. Combining the two, often as LC-MS, gives a complete picture.
What "third party tested" should mean
Independent testing means the analysis is performed by a laboratory that is not the manufacturer. That separation reduces the risk of biased results. When you review a COA, look for the testing lab, the methods used, and a batch number that matches your vial.
The Peptide Mart publishes batch specific results for every product. You can review them on our Quality page.
All products sold by The Peptide Mart are intended strictly for laboratory research use only. They are not for human or veterinary use, and nothing in this article is intended as medical advice.