A novel capillary electrophoresis method with pressure assisted field amplified sample injection in determination of thiol collectors in flotation process waters

A new capillary electrophoresis method was developed for the quantification of diisobutyldithiophosphate (DTP), diisobutyldithiophosphinate (DTPI) and ethyl and isobutyl xanthates (EX, IBX) all of which are used as thiol collectors in froth flotation. This method uses pressure assisted field amplified sample injection (PA-FASI) to concentrate the analytes at the capillary inlet. The background electrolyte in electrophoretic separation was 60 millimolar (mM) from 3-(cyclohexylamino)propane-1-sulfonic acid (CAPS) in 40 mM NaOH solution. The similar CAPS electrolyte solution has earlier been used for screening for diuretics that contained sulphonamide and/or carboxylic groups. In this study, the functional groups are xanthate, phosphate and phosphinate. The method was developed using actual flotation process waters. The results showed that the water delivered from the plant did not contain significant amount of collectors; therefore, method development was accomplished by spiking analytes in these waters. Separation of analytes was achieved in 15 min. The range of quantification was 0.27–66.6 mg/L (R2 0.9991–0.9999) for all analytes other than ethyl xanthate, for which the range was 0.09–66.6 mg/L (R2 0.9999). LOD (S/N = 3) and LOQ (S/N = 10) values for DTP, DTPI, IBX and EX were 0.05, 0.07, 0.06 and 0.01 mg/L and 0.16, 0.25, 0.21 and 0.04 mg/L, respectively. No interference from the matrices was observed, when the method was tested at a gold concentrator plant.