There are some other topics regarding this, but not specifically about "clean" kratom. There were some lab tests, but most of them won't show you all the info you need. I can tell you that at the moment EUkratom I regard highly, TheWildKratom is offline atm, and I trust ThomThom, but they let me down lately regarding effect quality, can't talk about how clean any of them are because it's hard to get those kind of tests...for me at least.