Beginner Guides • February 2, 2026
How to Evaluate a Peptide Vendor
COAs, purity testing, and red flags to watch for.
Part of the PeptidesATX Research Hub
Why Vendor Selection Matters
The quality of your research peptides directly affects the reliability of your results. A reputable vendor provides consistent, high-purity compounds with proper documentation. An unreliable vendor may supply degraded, contaminated, or incorrectly synthesized peptides that can waste time and resources.
This guide walks you through the key factors to consider when evaluating peptide suppliers.
Understanding Certificates of Analysis (COA)
A Certificate of Analysis is the most important document for verifying peptide quality. Here's what to look for:
Essential COA Components
- Purity percentage: Should be 98% or higher for research-grade peptides
- HPLC chromatogram: Visual data showing the purity analysis
- Mass spectrometry (MS) data: Confirms the correct molecular weight
- Batch/lot number: Allows traceability to specific production runs
- Date of analysis: Shows when testing was performed
- Physical appearance: Description of the lyophilized powder
How to Read HPLC Data
High-Performance Liquid Chromatography (HPLC) separates compounds based on their chemical properties. On a COA:
- Look for a single dominant peak (the target peptide)
- The area under this peak should represent 98%+ of total area
- Small additional peaks may indicate impurities or degradation products
Understanding Mass Spectrometry
Mass spectrometry confirms that the peptide has the correct molecular weight:
- The observed mass should match the theoretical mass for that peptide
- Small variations (typically <1 Da) are normal
- Significant differences suggest incorrect synthesis or contamination
Key Quality Indicators
1. Purity Level
Research-grade peptides should have:
- Minimum 98% purity for standard research applications
- 99%+ purity may be needed for specialized applications
- Purity should be verified by HPLC, not just claimed
2. Third-Party Testing
Independent testing provides unbiased verification:
- U.S.-based analytical laboratories are preferable
- Look for accredited testing facilities
- Third-party results should be available upon request
3. Batch-Specific Documentation
Every batch can vary slightly. Quality vendors provide:
- COA specific to each batch, not generic documents
- Unique lot numbers for traceability
- Consistent documentation format
4. Proper Storage and Shipping
How peptides are handled affects their quality:
- Lyophilized powder in sealed, light-protected vials
- Appropriate packaging for shipping
- Clear storage instructions provided
- Cold shipping when necessary
Red Flags to Avoid
Warning signs of unreliable vendors:
Documentation Issues
- No COA available or "upon request only" with no follow-through
- Generic COAs not specific to your batch
- Missing key data (purity, MS, or lot number)
- Documents that look altered or unprofessional
Pricing Concerns
- Prices significantly below market rate (quality has a cost)
- No pricing transparency
- Pressure to buy large quantities
Communication Problems
- Cannot answer questions about testing methods
- Unwilling to provide sourcing information
- No customer support or slow response
- Makes therapeutic claims about research compounds
Compliance Issues
- Provides dosing or administration instructions
- Claims products treat or cure conditions
- Doesn't clearly label products as research-only
Questions to Ask a Vendor
Before purchasing, consider asking:
- Can you provide a batch-specific COA?
- What purity level do you guarantee?
- Is testing performed in-house or by third parties?
- What are your storage recommendations?
- How are peptides shipped to maintain quality?
- What is your return policy for quality issues?
Evaluating Online Reviews
While reviews can be helpful, evaluate them critically:
- Look for detailed reviews that mention specific products
- Be wary of reviews that seem promotional or generic
- Consider reviews on multiple platforms
- Look for responses from the vendor to complaints
Our Quality Standards
At PeptidesATX, we provide:
- Batch-specific COAs for every product
- U.S.-based third-party laboratory testing
- Minimum 98% purity on all research peptides
- Clear labeling for research use only
- Responsive customer support
View our Certificates of Analysis or browse our research products.
Frequently Asked Questions
What should I look for in a peptide vendor?
Key factors include: batch-specific Certificates of Analysis (COA), third-party testing, transparent business practices, proper storage and shipping methods, clear labeling, and responsive customer support. Avoid vendors who cannot provide documentation or make therapeutic claims about research compounds.
How do I read a peptide COA?
A COA should show: purity percentage (look for 98%+), HPLC chromatogram data, mass spectrometry results confirming molecular weight, batch/lot number, date of analysis, and physical description. Compare the stated molecular weight to the expected value for that peptide.
What are red flags when buying research peptides?
Red flags include: no COA available, generic or non-batch-specific documentation, prices significantly below market rate, therapeutic claims or dosing instructions, poor packaging, no customer support, and inability to answer questions about testing methods or sourcing.
Why is third-party testing important?
Third-party testing provides independent verification of peptide quality. In-house testing can be accurate but may have bias. Independent laboratories provide unbiased confirmation of purity and identity, which is valuable for research reproducibility.
What purity level should research peptides have?
Research-grade peptides should typically have 98% purity or higher, verified by HPLC analysis. Some specialized applications may require even higher purity. Lower purity peptides may contain impurities that could affect research results.
How should peptides be shipped?
Lyophilized peptides should be shipped in sealed, light-protected vials. For temperature-sensitive compounds or longer shipping times, cold packs or dry ice may be appropriate. Packaging should protect against physical damage and contamination.
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Quality-Verified Research Peptides
All PeptidesATX products include batch-specific COAs and U.S. laboratory testing.
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This compound is intended for laboratory research use only. It is not approved for human or veterinary use.
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