HPLC vs LC-MS: How Peptide Purity and Identity Are Tested
For in vitro laboratory research use only. This article explains analytical methods only. Peptix makes no claims about the effects of any material it sells.
Two questions come up for any research peptide: is it the right compound, and how much of the sample is that compound? They sound similar, but they are answered by different analytical methods. On most peptide certificates, purity comes from HPLC-UV and identity comes from LC-MS.
Purity: HPLC-UV
HPLC stands for high-performance liquid chromatography. A small amount of the sample is prepared for analysis and pushed under pressure through a column packed with fine particles. Different components of the sample travel through the column at different speeds, so they come out (elute) at different times.
A UV detector at the end of the column records how much UV light is absorbed as each component comes out. The result is a chromatogram: a trace with a peak for each component.
Purity by HPLC-UV is the share of the main peak in the chromatogram, reported as a percentage. If the main peak accounts for 99.26% of the total peak area, the purity is reported as 99.26%.
What it tells you: how dominant the main component is in the tested sample.
What it does not tell you on its own: what that main component actually is.
Our HPLC purity explainer goes into more detail on reading a chromatogram.
Identity: LC-MS
LC-MS combines liquid chromatography with mass spectrometry. The chromatography step separates the sample as in HPLC. The mass spectrometer then measures the mass of the molecules coming off the column.
Every peptide has an expected molecular mass based on its amino acid sequence. LC-MS checks that the measured mass matches the expected compound. The result line on the certificate names what was identified.
What it tells you: whether the compound in the sample is the one expected.
What it does not tell you on its own: the purity percentage.
Why both are needed
Each method answers one half of the question:
| HPLC-UV | LC-MS | |
|---|---|---|
| Question answered | How much of the sample is the main component? | Is the compound the expected one? |
| Detection | UV absorbance | Mass |
| Typical result | Purity as a percentage | Identity named on the result line |
| Raw trace on COA | Chromatogram | Mass spectrum |
A high purity result alone could describe a sample made mostly of the wrong compound. A correct identity result alone could describe a sample with a lot of other material in it. Reported together, they give a fuller picture of the sample tested.
Size and mass
Mass also explains why identity results are so specific. BPC-157 is a 15-amino-acid peptide of about 1.4 kDa, while thymosin beta-4 is 43 amino acids and about 5 kDa. LC-MS identifies them at very different masses.
How this appears on Peptix certificates
The current lots listed on our COA page report both methods:
| Product | Lot ID | Purity (HPLC-UV) | Identity (LC-MS) | Measured net content per COA |
|---|---|---|---|---|
| BPC-157 10 mg | BC-20260521-01 | 99.26% | BPC-157 | 12.71 mg (labeled 10 mg) |
| TB-500 10 mg | TB-20260521-01 | 99.79% | thymosin beta-4 | 12.15 mg (labeled 10 mg) |
| BPC-157 / TB-500 20 mg | BB-20260521-01 | 99.15% | BPC-157 and thymosin beta-4 | 13.68 mg BPC-157 + 11.17 mg thymosin beta-4 (labeled 10 mg + 10 mg) |
Source: the Peptix COA page, Freedom Diagnostics reports dated July 8, 2026. A certificate reports results for the sample tested. It is not a guarantee for other lots.
The blend lot reports one purity figure and identifies both BPC-157 and thymosin beta-4 by LC-MS.
You can check each certificate on the peptide COA lookup page, or view the TB-500 10 mg product with its lot certificate. Browse all research peptides.
Frequently asked questions
What is the difference between HPLC and LC-MS?
HPLC-UV is used to measure purity, reported as the share of the main peak in the chromatogram. LC-MS is used to confirm identity by checking that the measured mass matches the expected compound.
What does HPLC purity mean?
HPLC purity is the share of the main peak in the chromatogram measured by high-performance liquid chromatography with UV detection, reported as a percentage.
Does HPLC confirm identity?
No. HPLC-UV shows how dominant the main component is. Identity is confirmed separately, usually by LC-MS.
Which methods are on Peptix certificates?
Current Peptix certificates report purity by HPLC-UV and identity by LC-MS.
For research use only. Not for human or animal use.
