Voltammetric detection of iodide after accumulation by Friedel's salt

Friedel's salt, a mineral anion exchanger belonging to the family of the la yered double hydroxides (LDHs), was synthesized and used as a novel electro de modifier for the accumulation of iodide species and their subsequent vol tammetric determination at carbon paste. Beside the preconcentration featur es of Friedel's salt towards iodide species, its presence at the electrode surface allowed to evidence the oxidation of molecular iodine into iodate ( with transient IO-), contrary to most carbon-based electrodes, as demonstra ted by cyclic voltammetry. Preconcentration was achieved at open circuit an d iodide was then detected by differential pulse voltammetry in unbuffered chloride medium. The sensing process was further improved by optimization o f the carbon paste composition, the detection medium, and the accumulation time. The detection limit was 0.06 muM (3a), with linear calibration ranges extending from 0.1 to 1 muM, 1 to 10 muM, and 10 to 50 muM, giving a dynam ic range of over several orders of magnitude. The effect of anionic interfe rences was evaluated and the sensor was applied to iodide analysis in synth etic ground- and seawaters.