  We analyze the diffusion of charged and neutral tracers suspended in an
electrolyte embedded in a channel of varying cross-section. Making use of
systematic approximations, the diffusion equation governing the motion of
tracers is mapped into an effective $1D$ equation describing the dynamics along
the longitudinal axis of the channel where its varying-section is encoded as an
effective entropic potential. This simplified approach allows us to
characterize tracer diffusion under generic confinement by measuring their mean
first passage time (MFPT). In particular, we show that the interplay between
geometrical confinement and electrostatic interactions strongly affect the MFTP
of tracers across corrugated channels hence leading to alternative means to
control tracers translocation across charged pores. Finally, our results show
that the MFPTs of a charged tracer in opposite directions along an asymmetric
channel may differ. We expect our results to be relevant for biological as well
synthetic devices whose dynamics is controlled by the detection of diluted
tracers.
