  Using the collective variables method we revisit the estimates of the
Ginzburg temperature for the Coulomb-dominated models of ionic fluids. We
consider the charge-asymmetric primitive model supplemented by short-range
attractive interactions in the vicinity of the gas-liquid critical point. For
this model, we derive the effective Ising-like $\phi^{4}$-model Hamiltonian
expressed in terms of the collective variables describing the fluctuation modes
of the total number density. We obtain the explicit expressions for all the
Hamiltonian coefficients within the framework of the same approximation,
namely, the one-loop approximation which produces the mean-field critical
parameters. Based on this Hamiltonian, we consistently calculate the reduced
Ginzburg temperature $t_{G}$ for both the pure Coulombic model (a restricted
primitive model) and the pure solvophobic model (a hard-sphere square-well
model) as well as for the model parameters ranging between these two limiting
cases. Contrary to the previous theoretical estimates, we obtain the reduced
Ginzburg temperature for the pure Coulombic model to be about 20 times smaller
than for the pure solvophobic model. For the full model including the
short-range attractive and long-range Coulomb interactions, we show that
$t_{G}$ approaches the value found for the pure Coulombic model when the
strength of the Coulomb interactions becomes large enough. Our results suggest
a key role of the Coulomb interactions in the crossover behaviour observed
experimentally in ionic fluids as well as confirm the Ising-like criticality in
the Coulomb-dominated ionic systems.
