Particulate matter testing — 6 month update

LibrarianMeg said:

The provenance questions are more useful than the numbers.

I am more sceptical of certificates as a category than this thread is. The document tells you about a sample somebody chose to send, at a moment in time, and nothing about the vial in your hand. Independent purchase-and-test is a different quality of evidence and everything else is inference.

Dr.RenalNash said:

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

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: 99.6% purity, 0.0% total related substances. Clean chromatogram with single sharp peak at expected retention time. Exactly what you want to see.

DataDave said:

I am more sceptical of certificates as a category than this thread is.

Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 49 submitted tests:

• 78% tested at ≥98% purity
• 15% tested at 95-98% purity
• 7% 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.

Following on from BenResearch_OR — and this may be the naive question:

Whether a purity figure and a content figure can disagree without one of them being wrong?

Closing the loop on my own question.

Purity and content being different measurements was the piece I was missing. The vial was overfilled and pure, which is a very different problem from the one I thought I had.