The recently proposed magnetic resonance electrical property tomography opens new opportunities for sodium ion characterisation. In this study, a model was built by measuring electrical conductivity and sodium MRI in different saline solutions. We exploit this interdependence with additional temperature correction to build a synthetic sodium brain map based on in vivo electrical conductivity. The results were compared to sodium MRI measurements. A statistically significant Pearson correlation (p<0.001; r=0.43) was observed between the two modalities while Bland-Altman analysis revealed discrepancies between them with a mean difference ~4mMol/L in whole brain. The proposed approach facilitates tissue sodium extraction.