Extended Data Fig. 1: Electron impact ionization mass spectrum of CH₃F.

There is no interference between the spectrum and CH₃D tracing at m/z 17 or other species in the m/z 16-30 range. The lack of interference and our near-perfect carbon mass balance confirm that there is no need for a full mass range scan to search for possible unknown species, as such species were either not present or did not interfere with mass traces associated with reactants and the primary product. The authors of ref. ¹ referred to the same database when raising their self-contradictory argument. We carefully consider EI fragmentation in our studies and select mass traces with minimum overlap (when possible). If present, EI interferences are readily addressable using the expected reaction rates and overlap percentages (available from the literature). Figure adapted with permission from ref. ²⁰, NIST Mass Spectrometry Data Center.