Third party lab testing not in house only

Proper HPLC or LC MS results included

Consistent crystal appearance fine uniform powder

No discoloration or clumping

Correct melting point range listed

Matching CAS number and molecular formula

Clear manufacturer origin not unknown source

Supplier reputation and history matter

No exaggerated purity claims e.g 100% pure

Transparency supplier answers technical questions confidently

Feedback from experienced users labs aligns

Absence of fillers or cutting agents

Low residual solvent levels