  Using different parameterizations of the nuclear mass formula, we study the
sensitivity of the isoscaling parameters to the mass formula employed in
grand-canonical calculations. Previous works on isoscaling have suggested that
the symmetry energy implied in such calculations is anomalously smaller than
that suggested by fits to nuclear masses. We show that surface corrections to
the symmetry energy naturally broadens the isotopic distribution thus allowing
for values of the symmetry energy which more closely match those obtained from
nuclear masses.
