Accepted answer
The question to ask is not whether a vendor is good but what evidence exists, of what kind, about which lots, from whom. Reputation is a compression of that evidence and it compresses badly.
Cost per milligram, worked honestly: a 10 mg vial at £34 is £3.40 per nominal milligram. If the content assay says 9.2 mg, that is £3.70 per actual milligram. If you then lose 4 µL of dead space per draw from a 2 mL fill across twenty draws, that is 80 µL or four per cent of the fill, taking you to £3.85. Add a £110 content assay amortised across the vial and it is £14.85 per milligram for the first vial of a new lot and £3.85 thereafter. The testing dominates, which is the actual argument for buying larger lots.
Certificate red flags and what each implies
| Observation | Implication | How to check |
|---|
| Lot number not on the vial | Certificate cannot be tied to your material | Photograph vial and certificate together |
| No method section | The number is not reproducible | Request column, gradient, wavelength |
| Purity to two decimals, no chromatogram | False precision | Request the trace |
| Test date before manufacture date | Certificate belongs to a different lot | Compare dates |
| Identical figures across lots | One certificate reused | Compare two lots side by side |
| “Sterile filtered” with no sterility test | Process claim substituted for a result | Ask for the sterility report |
What a verification listing at VendorInvestigate or a rating at PeptideMeter actually evidences is that some process was applied — which is more than nothing and considerably less than an audit. The useful question is what the process consists of and whether its inputs are independently obtained samples or vendor-supplied ones.
Where VendorInvestigate has documented verification processes, the value is in the audit trail rather than in the badge, and reading the process description is more informative than reading the outcome.
The limitation of the red-flag approach is that it is asymmetric: it identifies bad documentation reliably and good material only weakly.
The evidence you want is boring: the same result, from an independent laboratory, across more than one lot, over more than one year.
6Thank you — the worked example is what makes this usable. – s_bhattacharya 2 months ago 7Related: the same reasoning applies to the counter-ion question. – kwn_analytical 3 months ago add a comment