When looking at isolate, it is important to verify the purity. While many are in the 99.9+% range with no identifiable amounts of THC, there are lower purity ones (such as 99.5% or lower) that may still have trace amounts that show up on the labs. This small amount is typically negligible, and is nowhere near the amount usually found in full spectrum products. But it’s still something to be aware of for those seeking the purest they can find.
Zuardi, A. W., Crippa, J. A., Hallak, J. E., Bhattacharyya, S., Atakan, Z., Martin-Santos, R., … & Guimarães, F. S. (2012). A critical review of the antipsychotic effects of cannabidiol: 30 years of a translational investigation [Abstract]. Current Pharmaceutical Design, 18(32), 5,131–5,140. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/22716160