Definitions and methods of calculation of the temperature-programmed retention index, ITP III. A simplified calculation method based on the extended kováts definition

When the temperature-programmed retention index, I_TP, of a compound is calculated according to the Extended Kováts Definition, the net retention volume, V, of the compound should be used. However, it has been found that I_TP values calculated from the net retention time, t, are almost the same as those from V, and in general the differences are less than 0.5 i.u. The mathematical justification for this is presented. Therefore, for the calculation of I_TP, the substitution of t for V in the Extended Kováts Definition is not only very convenient in practice but also reasonable in principle.