Xanthates enhance the separation of valuable metals from minerals in hydrometallurgical processes. They degrade to structurally related decomposition products under the chemical and physical conditions in flotation processes, which minimizes the extraction recovery of metals. To monitor low quantities of the decomposition products, the flotation process requires sensitive, qualitative, or even quantitative controlling. The goal of the present research was to develop a sensitive separation method for on-line monitoring of the degradation of collector chemicals in the waters of a gold concentrator plant. To that end, an on-line coupling of capillary electrophoresis with a pressure-assisted field-amplified sample injection (PA-FASI) was developed. The purpose of the overall system set-up was to fortify concentrations during sample introduction in order to study xanthates and thiocarbonate directly in flotation waters during the process. The system developed from these methods was reliable and reproducible, enabling detection of below 10 mg L-1 quantities for ethyl and isobutyl xanthates as well as for isobutyl thiocarbonate. (C) 2015 Elsevier Ltd. All rights reserved.