Commentary on 'time-dependent selected reaction monitoring-based GC-MS/MS method for estimation of genotoxic impurities in a new antibacterial agent: alalevonadifloxin mesylate'

The references cited in this article to justify the analysis of alkyl mesylates in alalevonadifloxin mesylate (ALA) are considered totally inappropriate since they all present evidence showing that such esters are not formed during the synthesis of a sulfonic-acid salt using an alcohol as solvent. Relevant mechanistic and kinetic data, first published over a decade ago, demonstrate that no alkyl-sulfonate impurities are produced when an equimolar amount of methanesulfonic acid is added to the base form of a drug substance dissolved in ethanol (or a similar alcohol solvent), and so confirmatory assay data should not be required.