HPLC: The Purity Standard

High-performance liquid chromatography (HPLC) is the gold standard for measuring peptide purity. The peptide sample is pushed through a column under high pressure; different components travel at different speeds based on their chemical properties. The detector produces a chromatogram — a graph of peaks. The target peptide's peak area divided by the total area of all peaks gives the purity percentage.

Mass Spectrometry: Identity Confirmation

Mass spectrometry (MS) confirms identity, not purity. It measures the molecular weight of the compound and confirms it matches the theoretical molecular weight of the target sequence. HPLC + MS together answer both questions: this compound is the right molecule (MS) and it makes up ≥98% of the sample (HPLC).

What purity level should research peptides be?

The research standard is ≥98% purity, verified by HPLC (high-performance liquid chromatography). This level ensures that contaminants and synthesis byproducts are minimal enough to not interfere with research outcomes.

What is HPLC and why does it matter for peptides?

HPLC (high-performance liquid chromatography) is the gold-standard analytical method for measuring peptide purity. It separates the components of a sample and produces a chromatogram showing the percentage of the target compound vs. impurities.

What is mass spectrometry (MS) verification for peptides?

Mass spectrometry confirms the molecular identity of a peptide by measuring its molecular weight. HPLC tells you purity (how much of the compound is present); MS confirms identity (that the compound is what it's supposed to be). Together, HPLC + MS provide the most complete quality verification available.

What is a Certificate of Analysis (CoA) for peptides?

A Certificate of Analysis (CoA) is a document from the synthesizing or testing laboratory confirming the peptide's identity, purity (HPLC%), molecular weight (MS), and often additional properties. A legitimate CoA should be from a third-party or accredited lab.

What are common peptide synthesis impurities?

The most common impurities in synthetic peptides are deletion sequences, truncation sequences, oxidized residues (particularly methionine and cysteine), deamidated residues, and unreacted reagents. HPLC at ≥98% keeps these to a minimum.

Does peptide purity affect research results?

Yes, significantly. Impurities can have their own biological activity, creating off-target effects that confound results. For reproducible, interpretable research, ≥98% purity is the minimum reliable standard.

What should I look for on a peptide supplier's CoA?

Look for: HPLC purity ≥98%, MS confirmation of molecular weight, recent test date, testing laboratory name (third party or accredited), batch/lot number, and amino acid sequence. Reject suppliers who cannot provide a CoA or only provide manufacturer self-certification.

Peptide Purity: What ≥98% HPLC Means and Why It Matters for Research

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