Simultaneous determination of halide and thiocyanate ions by potentiometric precipitation titration and multivariate calibration

Halide and thiocyanate ions can be determined by a precipitation titration with silver nitrate as the titrant, and the end-point can be evaluated by a potentiometric method, in which generally a silver indicator electrode is used as the indicator electrode and a double-junction Ag-AgCl electrode as the reference electrode. However, when mixtures of halide and thiocyanate a re titrated, it is difficult to determine these components individually for there are overlapping steps in the potentiometric titration curves, especi ally in the case that there are obvious differences between concentrations of the components. In this paper, the linear equation for the potentiometri c precipitation titration of a mixture of halide and thiocyanate ions was d eveloped and it was then used for determining the components in the mixture s simultaneously with the aid of multivariate calibration methods. By appli cation of this model, 27 synthetic mixtures with three- and four-component combinations of chloride, bromide, iodide and thiocyanate with low concentr ation levels from 1.8x10(-4) to 6.2x10(-4) mol l(-1) were analyzed and acce ptable results were obtained. (C) 1999 Elsevier Science B.V. All rights res erved.