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When purchasing research peptides, you'll often see purity percentages like ">99%"—but what does this actually mean, and why does it matter for your work?
What is Peptide Purity?
Purity refers to the percentage of the target peptide relative to all other substances in your vial. A peptide with 99% purity contains 99% of the desired sequence, with only 1% consisting of related sequences, deletion sequences, or other impurities.
HPLC: The Gold Standard
High-Performance Liquid Chromatography (HPLC) is the industry standard for measuring peptide purity. This analytical technique separates compounds based on their interaction with a stationary phase, producing a chromatogram that shows:
- Main peak: Your target peptide
- Smaller peaks: Impurities and related sequences
- Area under curve: Quantifies relative amounts
The percentage purity is calculated by dividing the area of the main peak by the total area of all peaks.
Why Purity Matters
- Reproducibility: Higher purity means more consistent results across experiments
- Safety: Impurities can cause unexpected reactions or interference
- Accuracy: Knowing exact amounts is crucial for dose-dependent studies
- Cost-effectiveness: You're paying for active compound, not contaminants
Common Purity Grades
- >95%: Research grade, suitable for most applications
- >98%: High purity, preferred for sensitive assays
- >99%: Pharmaceutical grade, required for clinical applications
What to Look For in a COA
- Your Certificate of Analysis should include:
- HPLC chromatogram with clear peak identification
- Mass spectrometry data confirming molecular weight
- Endotoxin levels (should be <0.1 EU/mg)
- Net peptide content
- Batch number and testing date
Red Flags
- Be wary of suppliers who:
- Don't provide HPLC data
- Show purity without supporting chromatograms
- Can't explain their testing methodology
- Offer prices significantly below market rate
At Pure Peptide Labs, every batch undergoes rigorous HPLC testing with full documentation. Our partnerships with ISO 9001:2015 certified manufacturers ensure you receive consistently high-quality peptides for your research.