Abstract :
Plasticized poly(vinyl chloride) (PVC) membranes of different compositions were tested for use in the construction of potentiometric flow detectors for triiodide. A membrane with a 2:1 (w/w) 2-nitrophenyl octyl ether to PVC ratio was selected. The influence of thiosulphate in the carrier solution composition and of the flow-injection variables on the determination of triiodide was studied. In the selected conditions, a linear relationship between peak height and log[I3-] was obtained between 5 * 10^-6 and 1 * 10^-4 mol l^-1 triiodide. Peak height relative standard deviations for 2 * 10^-5 and 1 * 10^-4 mol l^-1 triiodide were ±0.4 and ±1.8%, respectively, and sampling frequency was 80 samples per hour. The method proposed was applied satisfactorily to the iodometric determination of different chlorine-containing disinfectants, among them trichloroisocyanuric acid and dichloroisocyanurate in several types of commercial sample.
