[en] This work utilizes pseudo-first order kinetics for the determination of iodine at the part per billion (ppb) levels. Flow injection (FI) system was developed and optimised for conditions in which the indicator reaction between Ce(IV) and As(III) gives first order kinetics. This oxidation-reduction reaction is catalysed by iodide ion and has been used for determination of trace levels of iodide for many years. Under pseudo-first order condition, analysis can be made in two ways, either a full kinetic or a fixed-time method. System development is presented as well as the characteristic evaluation of the kinetics. The system, with a simple and interferent-free in-line reduction step, has allowed successful quantitation of iodate, which has never been reported for this kinetic method. The system was used to determine total inorganic iodine in bottled drinking water that had been supplemented with iodate ion to the level of 100 μg I l^-1

[en] The electrochemical determination of iodide was studied at boron-doped diamond thin film electrodes (BDD) using cyclic voltammetry (CV) and flow-injection (FI) analysis, with amperometric detection. Cyclic voltammetry of iodide was conducted in a phosphate buffer pH 5. Experiments were performed using glassy carbon (GC) electrode as a comparison. Well-defined oxidation waves of the quasi-reversible cyclic voltammograms were observed at both electrodes. Voltammetric signal-to-background ratios (S/B) were comparable. However, the GC electrode gives much greater in the background current as usual. The potential sweep rate dependence exhibited that the peak current of iodide oxidation at 1mM varied linearly (r² = 0.998) with the square root of the scan rate, from 0.01 to 0.30Vs^-1. This result indicates that the reaction is a diffusion-controlled process with negligible adsorption on BDD surface, at this iodide concentration. Results of the flow-injection analysis show a highly reproducible amperometric response. The linear working range was observed up to 200μM (r² = 0.999). The detection limit, as low as 0.01μM (3σ of blank), was obtained. This method was successfully applied for quantification of iodide contents in nuclear emergency tablets

No abstract available

No abstract available

[en] A new apparatus, called 'membraneless vaporization' (MBL-VP) unit was designed and developed for direct analysis of solid samples. Solid analyte was converted into a gaseous form which then reacts with an indicator reagent. Change in absorbance was used to quantitate the analyte. Stirring with a magnetic bar was employed to facilitate the evaporation of the gas. Unlike the pervaporation technique, hydrophobic membrane was not required for this MBL-VP technique. Application of the membraneless technique for direct determination of calcium carbonate in calcium supplements, has shown to be very precise (R.S.D. = 2.5% for 0.16 mmol CO₃^2-), with detection limit of 0.5 mg CaCO₃. Results by this method agreed well with flame atomic absorption spectrometric method. Sample throughput was 20 samples h^-1