Quality Testing Explained
Understanding HPLC, mass spectrometry, COA interpretation, and how to verify peptide quality.
Why Quality Testing Matters
Peptide quality directly impacts research reliability. Poor quality peptides may contain:
- Impurities: Synthesis byproducts, degradation products
- Wrong peptide: Different sequence than labeled
- Contaminants: Bacteria, endotoxins, foreign materials
- Degraded product: Due to poor storage or old stock
Primary Testing Methods
HPLC (High-Performance Liquid Chromatography)
The most common purity test for peptides:
- What it measures: Percentage of target peptide vs impurities
- How it works: Separates compounds by their chemical properties
- Output: Chromatogram showing peaks for each compound
- Good result: 95%+ purity for research peptides, 98%+ for premium
Reading an HPLC Result
- Main peak: Should be dominant (>95% of area)
- Minor peaks: Represent impurities
- Retention time: When the peptide elutes (identifies it)
- Peak shape: Should be sharp, not broad or tailing
Mass Spectrometry (MS)
Confirms the peptide is the correct compound:
- What it measures: Molecular weight of the peptide
- Why it matters: Confirms identity, not just purity
- Output: Mass spectrum showing molecular weight peak
- Good result: Observed mass matches calculated mass (±1 Da)
| Method | Tests For | Limitation |
|---|---|---|
| HPLC | Purity percentage | Doesn't confirm identity |
| Mass Spec | Correct molecular weight | Doesn't show purity % |
| Both together | Identity + purity | Standard for quality |
Additional Testing
Amino Acid Analysis (AAA)
Breaks down peptide to verify amino acid composition:
- Confirms correct sequence building blocks
- More expensive, not always provided
- Important for complex or expensive peptides
Endotoxin Testing (LAL)
Tests for bacterial contamination:
- Important for injectable research compounds
- Measures endotoxin units (EU)
- Should be below detectable limits
Sterility Testing
Confirms absence of microbial contamination:
- Required for sterile-labeled products
- Not all research peptides are tested
Certificate of Analysis (COA)
What a Valid COA Contains
- Product name: Full peptide name and sequence
- Batch/Lot number: Unique identifier for production run
- Manufacture date: When produced
- Test date: When testing was performed
- Purity result: HPLC percentage
- MS result: Observed vs expected mass
- Appearance: Description of powder
- Lab identification: Testing facility name
COA Red Flags
- No batch number or generic "various"
- Same COA for all products
- No testing lab identified
- Missing HPLC chromatogram
- Suspiciously perfect 99.9% on everything
- Test date older than 1 year
Independent Testing
For critical research, consider independent verification:
- Janoshik Analytical: Popular peptide testing service
- University labs: May offer analytical services
- Commercial labs: Offer HPLC/MS testing
Cost Consideration: Independent testing typically costs $50-150 per sample. Worth it for expensive or critical research compounds.
Storage Impact on Quality
Even high-quality peptides degrade with improper storage:
- Lyophilized: Stable at -20°C for years, room temp for months
- Reconstituted: Use within 4-6 weeks, keep refrigerated
- Light exposure: Degrades many peptides - keep dark
- Contamination: Use sterile technique when handling