In the present study, the effect of the pairing interaction and the isovector correlation between nucleons on the properties of the isobar analogue resonances (IAR) in 112–124Sb isotopes and the isospin admixture in 100–124Sn isotopes is investigated within the framework of the proton–neutron quasi-particle random phase approximation (pnQRPA). The form of the interaction strength parameter is related to the shell-model potential by restoring the isotopic invariance of the nuclear part of the total Hamiltonian. In this respect, the isospin admixtures in the 100–124Sn isotopes are calculated, and the dependence of the differential cross section and the volume integral JF for the Sn(3He,t)Sb reactions at E(3He) =200 MeV occurring by the excitation of IAR on mass number A is examined. Our results show that the calculated value for the isospin mixing in the 100Sn isotope is in good agreement with Colo et al's estimates (4–5%), and the obtained values for the volume integral change within the error range of the value reported by Fujiwara et al (53 ± 5 MeV fm3). Moreover, it is concluded that although the differential cross section of the isobar analogue resonance for the (3He,t) reactions is not sensitive to pairing correlations between nucleons, a considerable effect on the isospin admixtures in N ≈ Z isotopes can be seen with the presence of these correlations.