  Mass-dependent and field shift components of the isotopic shift are
determined to high accuracy for the ground $1^1S-$states of some light
two-electron Li$^{+}$, Be$^{2+}$, B$^{3+}$ and C$^{4+}$ ions. To determine the
field components of these isotopic shifts we apply the Racah-Rosental-Breit
formula. We also determine the lowest order QED corrections to the isotopic
shifts for each of these two-electron ions.
