STRIPPING VOLTAMMETRIC DETERMINATION OF IODIDE WITH SYNERGISTIC ACCUMULATION AT A CARBON-PASTE ELECTRODE

Carbon paste electrodes (CPEs) of various compositions were studied to elucidate the stripping voltammetric behavior of iodide. At an accumu lation potential of +0.7 V (vs. Ag/AgCl), the CPE containing tricresyl phosphate as a pasting liquid was able to preconcetrate iodide effect ively via ion-pairing reaction followed by oxidation to iodine and its extraction onto pasting liquid. In a supporting electrolyte containin g 0.5 M NaCl and 0.1 M HCl, the reduction signal was proportional to i odide concentration from 5 x 10(-6) to 5 x 10(-7) mol/L with a detecti on limit of approximately 2.5 x 10(-7) mol/L (accumulation for 5 min). Other halides and pseudohalides did not interfere with the determinat ion, except for a high concentration excess of thiocyanate and bromide (100:1). The method was tested on model solutions and was applied to determine total iodine in samples of table salts and mineral water. Th e results were compared to those obtained by reference methods.