Purity Testing

Peptide Basics

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How do you know what’s actually in a peptide vial? Here’s how the industry tests for identity, purity, and safety — and what to look for in a Certificate of Analysis.

What to Look for in a Certificate of Analysis (CoA)

HPLC purity ≥ 95% (98%+ preferred for research)

Mass spectrometry (MS) confirmation of molecular weight

Lot/batch number matching the vial

Third-party laboratory name and accreditation

Endotoxin / LAL test result (EU/mg)

Water content (Karl Fischer)

Net peptide content (after water deduction)

Date of analysis

HPLC Purity Tiers

≥ 99%

Pharmaceutical Grade

Used in clinical trials and FDA-approved drugs. Rarely available for open-market research supply.

≥ 98%

Research Grade Premium

Highest quality routinely available. Preferred for critical assays and demanding research.

≥ 95%

Research Grade Standard

Acceptable for most research applications. The baseline minimum for reputable suppliers.

90–94%

Sub-Standard

Borderline acceptable. 5–10% unknown impurities. Seek higher purity when available.

< 90%

Unacceptable

Significant impurity load. Not suitable for serious research. Avoid.

Storage & Stability

Quick Reference

Educational Content Only. All Peptide Basics content is for research and educational purposes only. Nothing constitutes medical advice or instructions for human use.

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