Understanding Peptide Purity: HPLC, Mass Spec & COAs

Peptide purity is one of the most critical factors in ensuring reliable and reproducible experimental results. This guide explains the analytical methods used to verify purity and how to interpret the results.

High-Performance Liquid Chromatography (HPLC)

HPLC is the gold standard for peptide purity analysis. It separates a peptide sample into its individual components based on their physicochemical properties, allowing researchers to quantify the percentage of the target peptide versus impurities. Research-grade peptides should show ≥98% purity on the HPLC chromatogram.

Mass Spectrometry (MS)

Mass spectrometry confirms the molecular identity of the peptide by measuring its mass-to-charge ratio. The observed molecular weight should match the theoretical value calculated from the amino acid sequence. Electrospray ionization (ESI-MS) and MALDI-TOF are the most common techniques used for peptide characterization.

Reading a Certificate of Analysis (COA)

A proper COA should include: - Peptide sequence and molecular formula - HPLC purity percentage with chromatogram - MS data confirming molecular weight - Batch/lot number for traceability - Appearance and solubility data - Testing laboratory name and date

At CopenhagenChems, we provide COAs from independent third-party laboratories for every batch, ensuring complete transparency and scientific integrity.

Why Purity Matters

Even small impurities can dramatically affect experimental outcomes. Truncated sequences, deletion peptides, and oxidized variants may exhibit different binding properties, leading to false positives, inconsistent dose-response curves, or misattributed biological activity. Always verify purity before starting critical experiments.