The established assessment of purity inventions has been that increased purity of chemical compounds was only considered novel, if the claimed high purity could not be achieved by conventional means. Recent EPO Board of Appeal decision T0043/18 has ruled that this approach contradicts the overarching principles of novelty, and found instead that novelty can only be destroyed by a clear and unambiguous disclosure in the prior art. This approach was also found in earlier EPO Board of Appeal case T1085/13. Interestingly, this approach is out of line with the current EPO Guidelines for Examination. However, patent applicants should be aware that even if the approach set out in T0043/18 and T1085/13 is followed, it can be difficult to convince Examiners of the inventiveness of purity inventions, especially where a claimed purity level was achievable through conventional means.