The development of new heavy-ion accelerators has enabled a wider range of short-lived isotopes to be produced. To measure
yields of these isotopes and study nuclear reaction mechanisms has demanded fast on-line chemical separations from chemists.
This article reviews some of the techniques that have been introduced in recent years to achieve this. Reference is made to
the use of on-line mass separators, helium gas jets and more classical methods carried out in second time scales.