Sequential injection system for simultaneous determination of chloride and iodide by a Grans plot method

This paper describes an automated set-up based on the sequential injection analysis (SIA) concept with potentiometric detection for the determination of chloride and iodide at low concentrations. The assessment of both ion concentrations is accomplished by titration with silver ions using the Granʹs plot approach. The proposed procedure enables chloride and iodide to be determined simultaneously in the range 6.0×10^-6 to 1.0×10^-4 mol l^-1 if a minimum silver concentration in the volumetric solution is chosen (5×10^-5 mol l^-1). Conventional titrations based on the first derivative evaluation of the equivalence points applied to the same solutions fail, especially for chloride determinations. Although, a comparison of results obtained for higher analyte concentrations shows that they have similar accuracy and precision.