Transport extraction based on solvent sublation has been used for a 400-fold preconcentration of iodide from aqueous samples into an immiscible organic solvent. Separation efficiencies amounting up to 95% were obtained for iodide concentrations of 1-10 mg/l, independent of the volume of the aqueous samples in the range of 1-4 l. Iodide was oxidized to iodine, which was subsequently transport-extracted as an ionic associate with the cationic surface-active agent N-cetylpyridinium chloride into 10 ml of benzene. The effect of various parameters (concentration of iodide, bubbling time, N2-gas flow-rate, volume of the aqueous phase) on transport extraction was investigated. Kinetic investigations showed that the transport-extraction process essentially follows a modified Langmuir adsorption model, which makes it possible to calculate the mass-transfer rate constant of the process for each particular case.
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