HPLC Purity Explained: What a Purity Percentage Means
HPLC Purity Explained: What a Purity Percentage Means
For in vitro laboratory research use only. This guide is for information only. Peptix makes no claims about the effects of any material it sells.
Certificates of Analysis for research peptides usually report a purity percentage measured by HPLC-UV. This guide explains what that number measures, what it doesn’t, and how it fits with the other results on a certificate.
What HPLC-UV is
HPLC stands for high-performance liquid chromatography. A dissolved sample is pushed through a column that separates its components, and a UV detector records them as peaks over time. The result is a chromatogram.
What the purity percentage measures
On a COA, purity (HPLC-UV) is the share of the main peak in the chromatogram measured by high-performance liquid chromatography with UV detection, reported as a percentage. In simple terms, it compares the size of the main peak with the total of all peaks the detector recorded.
What it doesn’t measure
- Identity. A purity percentage alone doesn’t show what the main peak is. That’s the job of the identity test, which on Peptix certificates is LC-MS (liquid chromatography with mass spectrometry), used to check that the measured mass matches the expected compound.
- Amount. Purity is a proportion, not a quantity. The amount the lab measured in the tested vial is reported separately as net content, as printed on the certificate. It can differ from the labeled amount stated on the product label.
- Components the detector doesn’t see. UV detection records components that absorb UV light under the method’s conditions. Water and some salts, for example, aren’t reflected in the purity percentage. This is one reason purity and net content are reported as separate results.
- Other lots. A certificate reports results for the sample tested. It is not a guarantee for other lots.
Reading purity alongside the rest of the COA
Peptix certificates report purity, identity and net content for one stated lot. Check that all three refer to the lot number on your vial. See How to Read a Certificate of Analysis for a field-by-field walkthrough.
Peptix certificates
The lots listed on our COA page each have a third-party Certificate of Analysis showing the lot number, HPLC-UV purity and LC-MS identity.
Related
All Peptix products are sold for in vitro laboratory research use only. Not for human or animal use.
