Peptide purity testing by HPLC

What a purity test answers

Synthesis leaves things behind: truncated and deletion sequences, incomplete deprotection, oxidized residues, residual solvent. HPLC is what separates “mostly the peptide” from “90% the peptide”, and a single percentage point matters. 99% and 98% are different specifications.

How we run it

Purity runs on reversed-phase HPLC with UV detection at 214 nm, the wavelength the peptide bond absorbs at, using area normalization. That is the same basis suppliers quote their own figures on, so our number and theirs can be compared directly.

Column chemistry, gradient and detection wavelength are printed on the certificate. If you want to reproduce the work elsewhere, you have what you need.

Reading the number

HPLC purity is area percent: a relative measure of the UV-absorbing species in the sample. It says nothing about water, salts or counter-ions, which is why a 98% peptide can still be well under 98% of the vial by weight. If the amount in the vial matters to your work, add a content test.

We do not issue a grade. The certificate carries the measured area percent and the full peak table, and the conventional purity bands are explained on our home page.

What the certificate reports

• Purity as HPLC area % at 214 nm
• An annotated chromatogram and the full peak table
• Column, gradient and detection conditions
• The named analyst
• A COA number anyone can check at Verify a COA

How to order

1. Create a free account. Individual or business; an individual account needs only an email address.
2. Build the order and submit it. One row per sample. Choose a package that includes purity, or add it to any sample.
3. Get your chain-of-custody form and payment link. Both are emailed the moment you submit and saved on the order in your account.
4. Post the vials. Write each Sample ID on its vial and on the package, and add your tracking number to the order.

Sample requirements

For lyophilized powder, 2 mg or more per vial is ideal; we can usually work with less and will tell you before we start if the amount is marginal. For reconstituted solution, send at least 0.5 mL. This test is subdivided from the same vial as the sample’s other tests. Pro 7X takes two vials of the same sample, because it includes sterility.