Dr.DermMIA said:

My vendor review relevant to certificates of analysis: ordered 3 times from my current compounder.

HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean:

• Purity %: Should be >97%. Below 95% is concerning.
• Retention time: Should match reference standard for the peptide
• Related substances: Degradation products should be <2% total
• Single impurity: No individual impurity should exceed 1%

My last batch: 99.3% purity, 0.3% total related substances. Clean chromatogram with single sharp peak at expected retention time. Exactly what you want to see.

LindaRN_retired said:

One addition: an unstated method makes a report close to uninterpretable.

Genuinely useful, thank you. I had the facts and not the framework.

Dr.DermMIA said:

My vendor review relevant to certificates of analysis: ordered 3 times from my current compounder.

Third-party testing services for certificates of analysis besides Janoshik:

• Janoshik: Gold standard for peptide community, ~$124, 10-14 day turnaround
• Valitech: US-based, ISO 17025 accredited, ~$244
• Eurofins: Full pharmaceutical testing suite, more expensive but comprehensive
• ChemTox: Basic identity and purity testing, ~$114

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.

Dr.EndoIndy said:

Two reports on the same product from two laboratories, four percentage points apart, and no method stated on either.

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: 15.8 minutes (consistent with semaglutide reference standard)
Peak purity: 98.1%
Related substances: 0.4% (single impurity at 9.6 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.

Moderator note: good thread. Keeping it here rather than moving it, because the question is general enough to be useful.