Adding the clinical framing, because it changes how the question reads.
Vendor quality matters when discussing certificates of analysis. I've tested my last 5 batches through Janoshik and purity has ranged from 98.6% to 99.6%. Consistency is key.
For anyone new: always request the COA, and consider independent verification. The $300 for a Janoshik test is worth the peace of mind.
Dr.SportsMedIN said:My vendor review relevant to certificates of analysis: ordered 5 times from my current compounder.
Third-party testing services for certificates of analysis besides Janoshik:
- Janoshik: Gold standard for peptide community, ~$148, 10-14 day turnaround
- Valitech: US-based, ISO 17025 accredited, ~$218
- Eurofins: Full pharmaceutical testing suite, more expensive but comprehensive
- ChemTox: Basic identity and purity testing, ~$118
Janoshik is the community standard but any ISO-accredited analytical lab can verify peptide identity and purity. The key is independence — don't rely solely on the vendor's own testing.
Sigma-Aldrich — Research-Grade Standards
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference Standardskate.chem said:Inter-laboratory variation comes from real methodological differences, not sloppiness: which reference standard was used and how it was itself…
My HPLC chromatogram analysis for certificates of analysis — I sent my batch to Janoshik and here's what the results showed:
Main peak retention time: 15.2 minutes (consistent with semaglutide reference standard)
Peak purity: 99.1%
Related substances: 0.8% (single impurity at 9.1 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.6 (matches expected molecular weight)
This is a clean result. The mass spec confirmation is particularly important — it proves the molecule is actually semaglutide and not a substitution.