Peptide Quality Testing: HPLC Purity, MS Identity & Lot Documentation

BluGen releases research peptides on documentation, not on trust. Before a lot enters inventory it is characterized by four analytical methods and re-tested at receiving. This page explains what each test measures, the acceptance criteria a lot must meet, and how the results reach you on the lot-specific certificate of analysis (CoA).

The four numbers that define a lot

A research-grade peptide lot is defined by identity, purity, net peptide content, and water content, with a residual-solvent panel underneath. Each is produced by a different instrument because each answers a different question.

1. Identity — ESI mass spectrometry

Electrospray-ionization mass spectrometry (ESI-MS) confirms that the molecule in the vial is the sequence on the label. The observed mass is compared against the calculated monoisotopic mass for the published sequence; modifications (acetate counterion, palmitoylation, C-terminal amidation) are confirmed by the expected mass shift. A lot only releases when the observed mass aligns within method tolerance and the charge-state envelope is consistent with a single peptide species.

2. Purity — reverse-phase HPLC

RP-HPLC at 214 nm (the peptide-bond absorbance) separates the target peptide from synthesis-related impurities and reports an area-percent purity. The standard release specification is ≥98% area purity, and most catalog lots test at ≥99%. The exact figure is printed on each lot CoA — see the CoA Library to verify a specific lot.

3. Net peptide content

HPLC purity is not the same as mass-on-vial. A lyophilized cake contains water, counterion, and trace solvent, so the gross vial mass overstates active peptide. Net peptide content (reported as a percentage) lets you calculate the true molar amount for reconstitution. The reconstitution calculator uses this to convert vial size and diluent volume into concentration.

4. Water content — Karl Fischer

Coulometric Karl Fischer titration measures residual water in the lyophilized cake. Water content drives both stability and the net-peptide calculation, and is reported on every CoA.

Residual solvents — gas chromatography

Synthesis solvents (acetonitrile, TFA, DMF, methanol) are quantified by GC against ICH Q3C class-3 limits. Lots over the limit are not released.

Re-testing at receiving

Every incoming lot is independently re-tested at receipt against the manufacturer CoA for HPLC purity, MS identity, and water content before it enters inventory. Lots that fail re-test never ship. The full chain — manufacturer lot, re-test record, inventory lot, shipped lot — is retained for the advertised stability window. See supplier qualification for the upstream process.

FAQ

Can I get the HPLC chromatogram, not just the summary?

Yes. Lot chromatograms are available to qualified institutional buyers on request alongside the standard CoA.

Why does the homepage say ≥99% but the methodology page says ≥98%?

≥98% is the release floor every lot must clear; ≥99% is what most lots actually test at. The CoA reports the exact measured purity for the lot you receive.

Do you test every lot or sample across lots?

Every lot is tested and re-tested. Documentation is lot-specific, not batch-averaged.