Inter-lab variability in peptide testing — July 2024

Dr.AddMedPHL said:

I tested my certificates of analysis batch through Janoshik — 97.3% purity.

My vendor review relevant to certificates of analysis: ordered 6 times from my current compounder. Consistency has been excellent.

Shipping: 3-day with temperature monitor
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 99.3% average across orders (Janoshik verified)
Customer service: Responsive within 1 hours
Price: $155/month for semaglutide 1.7mg equivalent

nancy_portland said:

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

This answered a question I did not know how to ask. I will report back once I have actually tried it.

Dr.AddMedPHL said:

I tested my certificates of analysis batch through Janoshik — 97.3% purity.

Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 46 submitted tests:

• 82% tested at ≥98% purity
• 12% tested at 95-98% purity
• 6% tested at <95% purity (concerning)

The vendors with consistently high purity results are listed in the Vendor Directory. We update monthly based on new community submissions.

PedsEndoPhilly said:

I have a certificate reporting 99.2% purity and 6.1mg content on a vial sold as 5mg, and I cannot work out whether those two numbers are consistent or…

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: 99.4% purity, 0.0% total related substances. Clean chromatogram with single sharp peak at expected retention time. Exactly what you want to see.

Moderator note: a couple of off-topic posts removed.