Dr.PeteFamMed said:They are not contradictory, they measure different things, and this is the single most common misreading of a certificate.
Agreed, and mass spec answers a question purity does not: identity. High purity tells you one thing dominates the chromatogram, not that it is the molecule you ordered. A mass within about a dalton of expected is the identity check.
Dr.SleepRoch said:Right, and one flattering data point from a group buy is not consistency.
This answered a question I did not know how to ask.
Dr.PeteFamMed said:They are not contradictory, they measure different things, and this is the single most common misreading of a certificate.
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.
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Shop Reference StandardsLarryQC_SD said:Six orders from the same supplier over eight months, every one independently tested, and the consistency is the part worth reporting rather than any…
Vendor reputation tracking for vendor vetting: I maintain a personal spreadsheet with every order I've placed — date, vendor, batch number, Janoshik result, personal efficacy assessment (1-5 scale), and any issues.
After 18 orders across 3 vendors: average purity 97.2%, zero sterility concerns, 1 shipping issues (all resolved). This data gives me confidence in my current source and documentation if issues arise.
I encourage everyone to track their orders systematically. Community data aggregation makes us all safer.
Moderator note: good thread. Keeping it here rather than moving it, because the question is general enough to be useful. Thread quality here is what the rules are for. Keep it up.