[en] The Thomas binary encounter approach (BEA) has been applied to obtain modified energy transfer limits in ion-atom collisions. These limits can be used in the Gryzinski model to calculate cross sections of single charge transfer and single impact ionisation. A suitable three-dimensional correction factor is found to follow directly from the Thomas BEA, providing a consistent means of calculating both cross sections from the electron removal cross sections. The present analysis is discussed in comparison with some recent papers. (author)