Pastor Peptide
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Mass Testing

Mass and Purity

1. Mass Testing (Identity Confirmation)

Purpose:

  • To confirm the molecular weight matches the intended peptide sequence.
  • Ensures the compound isn’t mislabeled, mis-synthesized, or degraded.

How it’s done:

  • LC-MS (Liquid Chromatography–Mass Spectrometry) is the gold standard.
    • Liquid Chromatography (LC): Separates the sample into individual components.
    • Mass Spectrometry (MS): Measures the molecular mass of each component.
  • The resulting spectrum shows a peak at the expected mass (± a small error margin).
  • Example: A 1,295.6 Da peptide should have a dominant peak at ~1,295.6, confirming it’s correct.

What to look for in a COA:

  • “Observed mass” should match the “Theoretical mass” within 0.1–0.5 Da.
  • Sometimes shown as a % “Mass Match” score.

2. Purity Testing

Purpose:

  • Measures how much of your sample is the target peptide versus impurities.
  • Impurities can include:
    • Truncated sequences (shorter peptides from incomplete synthesis)
    • Side products from incorrect amino acid coupling
    • Residual solvents or synthesis reagents

How it’s done:

  • HPLC (High-Performance Liquid Chromatography) is most common.
    • Separates components by polarity and retention time on a chromatography column.
    • The output chromatogram shows peaks for each substance.
    • The area under the main peak vs. all peaks combined = purity %.

What to look for in a COA:

  • Purity is usually given as a percentage:
    • ≥ 98% = Pharmaceutical grade
    • 95–98% = High research grade
    • < 95% = Lower research quality (may be fine for some in vitro work but not in vivo)
  • Example: “Purity (HPLC): 98.4%” means 98.4% of the sample is the intended peptide.

Why this matters for peptides

  • Mass testing makes sure you have the right molecule.
  • Purity testing makes sure you have mostly that molecule and not a bunch of byproducts.
  • Without both tests, you could have:
    • Wrong sequence entirely (wasted research)
    • Impurities that affect biological results
    • Dangerous contaminants if injected