More than likley to be on the safe side . This is because they sometimes put additives in there nitromethane from methanol to oil. I would think a 99% mixture would still have something added to it. Distill it, see if anything comes over better to be safe than sorry . Also there is some good information in this post about nitromethane.
https://www.thevespiary.org/rhodium/Rhodium/chemistry/mdma.drdrool.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/mdma.drdrool.html)