In the present study the effect of adding sodium di-ethyldithiophosphate (DTP) to sodium isobutyl xanthate (SIBX) as a co-collector in the flotation of a platinum group mineral (PGM) ore was studied with a view to investigating whether there was any evidence of a synergistic beneficial effect resulting from the use of the mixture. Flotation tests were carried out using single collectors as well as various mixtures of the collectors at different but constant total molar concentrations. Size-by-size analyses of the concentrates were carried out in all cases. After deconvoluting the results of the different flotation tests there was no conclusive evidence of a synergistic effect when using mixtures. The DTP was shown to cause an increase in the recovery of fine particles (<25 mu m) and this is ascribed to its effect on the behaviour of the froth phase. It was concluded that the effect of the addition of the DTP was to stabilise the froth phase and that this was a parallel reaction and not a result of any synergistic interaction between the SIBX and DTP. (C) 2012 Elsevier Ltd. All rights reserved.