At atmospheric pressure (AP)ions are subject to a high frequency of collisions with bulk gas particles and other species present.Due to the high number of collisions,even relatively slow chemical reactions may become relevant in an AP ion source.The length of the ion migration path is directly correlated with the absolute number of collisions, therefore it may serve as a figure of merit to estimate the relevance of individual chemical interactions. In addition the experimental investigation of ion transfer times allows the verification of complex numerical models, which consider transport due to electrical fields and viscous gas flow.