Every Peptide Reference Question Answered, in 19 Studies

19 referenced articles

• Are Peptides Legal in the UK?1 sources
• Are Peptides Steroids?1 sources
• Are Peptides Safe? It Depends Entirely on Which One2 sources
• Peptides and Muscle Growth: Claims Against Evidence2 sources
• Endotoxin: The Contaminant That Is Not a Protein3 sources
• What a Clean Mass Spectrum Does Not Prove3 sources
• Aspartimide Formation and Why It Hides3 sources
• The Method That Measures Peptide Directly2 sources
• Net Peptide Content: The Number That Says How Much You Have3 sources
• Research Peptides and Collagen Peptides Compared3 sources
• Oligopeptide, Polypeptide, Protein2 sources
• Peptide Terminology: The Words That Recur2 sources
• Lyophilisation: Why Peptides Arrive as Powder2 sources
• How to Read a Certificate of Analysis3 sources
• HPLC and Mass Spectrometry: What Each Answers3 sources
• HPLC Testing for Peptides3 sources
• How Peptides Are Made3 sources
• Peptides: A Complete Reference Guide3 sources
• What Is a Peptide?2 sources

Open research questions

• What is a research peptide?
• How is peptide purity measured?
• Why is HPLC the standard purity assay?
• What information is on a peptide CoA?
• Why are research peptides lyophilised?

Deep dive: what 'peptide' actually means

A peptide is a short chain of amino acids linked by peptide bonds, typically 2–50 residues. Above that boundary the molecule is usually called a protein. Peptides can be endogenous (produced by the body) or synthetic (manufactured by solid-phase peptide synthesis, SPPS). The 'research peptide' category refers specifically to synthetic peptides supplied for laboratory use — not medicines, not supplements.

Why HPLC and mass spec together

HPLC (High-Performance Liquid Chromatography) reports the purity of a batch by measuring what percentage of the sample matches the target peptide's retention time. Mass spectrometry independently confirms the target's molecular weight. Together they answer two different questions: 'is it clean?' and 'is it the right molecule?'. A CoA that reports only one is incomplete.

How to read a Certificate of Analysis

A complete peptide CoA lists: batch number, HPLC purity (area %), mass-spec measured mass vs theoretical, water content (Karl Fischer), acetate/counterion content, appearance, and often endotoxin and residual solvents. Learn to spot the missing fields — that's usually where quality claims fall apart.

Handling checklist

• Confirm HPLC ≥98% and mass-spec identity on CoA
• Store lyophilised at −20 °C long-term
• Reconstitute with bacteriostatic or sterile water only
• Aliquot to minimise freeze/thaw cycles
• Label vials with date, concentration, and batch

Common mistakes

Buying a peptide without a CoA

Insist on an in-batch HPLC + mass-spec certificate before purchase.

Using DI water for reconstitution

Use bacteriostatic (0.9% benzyl alcohol) or sterile water only.

Storing lyophilised vials at room temperature long-term

Freeze at −20 °C; short-term 2–8 °C is acceptable for weeks, not months.