Peptide purity explained: COA and HPLC

A purity percentage only means something if you know how it was measured. This guide explains what HPLC and mass spectrometry measure, what a proper Certificate of Analysis (COA) contains and how to tell a reliable certificate from a meaningless document.

What HPLC measures

In HPLC (high-performance liquid chromatography) a dissolved sample is pumped through a column under high pressure. Molecules with different properties leave the column at different times and appear as peaks in a chromatogram.

Purity is the area of the main peak (the peptide) divided by the total area of all peaks. A narrow, dominant main peak with hardly any side peaks indicates a pure product.

Mass spectrometry confirms identity

HPLC shows how pure a substance is, not which substance it is. Mass spectrometry (MS) measures the molecular mass; when it matches the peptide's theoretical mass, identity is confirmed. A proper COA includes both.

What a proper COA shows

A reliable certificate lists:

• product name, batch/lot number and manufacturing date
• HPLC result with purity percentage, ideally with the chromatogram
• MS result with measured and theoretical molecular mass
• appearance (for example white lyophilised powder)
• testing laboratory, test date and signature or stamp

≥98% or ≥99%: what's the difference?

One percentage point sounds small, but it can mean up to half the impurities. For reproducible research every fraction counts: impurities may have activity of their own or distort the measured concentration. Every Virexa Labs batch ships at ≥99% purity.

Batch numbers and traceability

The batch number on your vial should match the certificate, so you know the analysis really covers your product. Our verification page explains how to check a Virexa Labs product is genuine.

Red flags on a certificate

Be careful with:

• a COA without batch number or lab name
• exactly 100.00% purity – practically impossible
• an HPLC result with no identity confirmation
• the same certificate for different products or batches

Research peptides at ≥99% purity

• BPC-157
• Semax
• KPV
• MOTS-C

Frequently asked questions

What does ≥99% purity mean?

At least 99% of the peak area in the HPLC chromatogram is the intended peptide.

Why are both HPLC and MS needed?

HPLC measures how pure the product is; mass spectrometry confirms which molecule it is.

Can I request the COA for my batch?

Yes – contact us with your order and batch number and we'll send the certificate.