Supplier evaluation for research materials comes down to what a supplier can evidence rather than what they assert. Marketing language is cheap; a matching batch record is not.
Ask first for documentation tied to a specific batch. A supplier able to produce a certificate that matches a batch number you name is demonstrating a working system. One that offers only generic documentation, or the same document for every batch, is not.
Ask how storage and handling are managed between receipt and dispatch. You do not need a facility tour, but you should get a specific answer rather than a reassurance.
Ask what happens when something is wrong. A supplier with a defined process for damaged, incorrect, or undocumented material has thought about failure; one that has never considered it will improvise at your expense.
Be realistic about which gaps matter. A newer supplier may not yet have certificates uploaded for every historical batch, and saying so openly is a better signal than a complete-looking set of documents that cannot be verified. What should disqualify a supplier is a claim they cannot support when asked directly.
References
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