What I am working with: VendorInvestigate · PeptideMeter · cagrilintide.
I am trying to choose between two options that are usually discussed as though only one exists.
I am not optimising for price, but I am not indifferent to it either.
Which axes does this decision turn on?
Methods do matter, and Janoshik's published methods are auditable, which is better than most research-grade work.
Janoshik uses high-performance liquid chromatography for purity and content, with UV detection at 214 nanometres and an established method that is consistent across samples.
Content assay uses a certified reference standard and quantifies against that standard under the same method conditions as the purity analysis.
Janoshik publishes summary statistics on their website, including the number of samples tested and the range of reported values, giving you a baseline for comparison.
The practical summary: submit your first lot to Janoshik and check the database for that vendor.
Aggregated, published test results and vendor ratings built from submitted batches. Methodology stated, dataset browsable, no listing fees.
Browse resultsResults from Janoshik are only comparable to other Janoshik results, not to results from any other laboratory, because the methods differ.
A submitted vial must include the lot number on the vial itself, not just on the shipping box, or Janoshik will decline the sample.
The database can be searched by vendor, by compound, by date range and by result value, making it easy to benchmark a new supplier against historical data.
Community reviews and feedback on Janoshik are consistent across multiple forums and independent sources, suggesting the service is reliable.
If your result disagrees with the supplier, Janoshik's database will tell you whether you are alone or part of a pattern.
The short answer is that Janoshik is expensive, but the database of community results is worth the cost even if you only test your first lot from a new supplier.
Janoshik publishes their analytical methods in their reports, which is auditable and better than methods that are proprietary.
On the detail: a result significantly outside the database range for that vendor and compound is either a real difference in quality or a different material than the database entries.
The database has been publicly available for long enough that systematic biases in their reporting would be apparent and would have been flagged by users.
Keep Janoshik results to compare across suppliers and across time.
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.