Inter-lab variability in peptide testing — July 2024

Adding the clinical framing, because it changes how the question reads.

My vendor review relevant to certificates of analysis: ordered 4 times from my current compounder. Consistency has been excellent.

Shipping: 2-day priority with gel ice
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 99.5% average across orders (Janoshik verified)
Customer service: Responsive within 4 hours
Price: $157/month for semaglutide 1.7mg equivalent

Dr.PulmRoch said:

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

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

• Janoshik: Gold standard for peptide community, ~$156, 10-14 day turnaround
• Valitech: US-based, ISO 17025 accredited, ~$206
• Eurofins: Full pharmaceutical testing suite, more expensive but comprehensive
• ChemTox: Basic identity and purity testing, ~$116

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.

One thing that is still open after Dr.PulmRoch’s answer:

How would you tell the difference between that and the alternative explanation?

DataDave said:

Third-party testing services for certificates of analysis besides Janoshik: Janoshik: Gold standard for peptide community, ~$156, 10-14 day turnaround…

Reconstituted peptide stability data for certificates of analysis: I had Janoshik test my reconstituted vial at day 1, day 14, and day 28 stored in the refrigerator.

Day 1: 99.2% purity
Day 14: 98.6% purity
Day 28: 98.4% purity

Minimal degradation over 28 days when properly refrigerated. This confirms the standard 28-day beyond-use date is appropriate. Beyond 28 days, I'd reconstitute a fresh vial to be safe.

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