Abstract:
Using multiple low-cost detectors in flow injection analysis can reduce the cost per analysis. Ion-selective electrodes make good detectors, and electrodes with crystalline membranes often need little maintenance. The response of chloride, bromide, and iodide selective electrodes to the mutually interfering chloride and bromide are modeled by the Nikolskii equation. It is shown that, although the Nikolskii equation do not model the electrode potentials without bias, the precision of the predicted concentrations are determined more by the error propagation properties of the calibration procedure than by the lack of fit of the model to the experimental potentials. Fluoride- and chloride-selective electrodes detect the non-interfering chloride and fluoride ions. The properties of a flow-injection system for the routine determination of fluoride and chloride were investigated and it was found that the flow-cell geometry, electrical earth connection, and streaming potentials influence the quality of analysis.
