  We consider a two dimensional Turing like system with two diffusing species
which interact with each other. Considering the species to be charged, we
include the effect of an electric field along a given direction which can lead
to a drift induced instability found by A.B.Rovinsky and M.Menzinger\cite{9}.
This allows one to study the competition between diffusion and drift as was
done numerically by Riaz et al. We show here that an analytic formula can be
found on the basis of a linear stability analysis that incorporates all the
effects that are known for the system and also allows for some detailed
predictions.
