Indirect voltammetric detection of fluoride ions in toothpaste on a comb-shaped interdigitated microelectrode array

A novel technique based on dynamic electrochemistry for the detection of fluoride ions was developed. It is based on its strong complexation with ferric ion. Formed fluoroferric complex is cathodically inactive at the potential of the reduction of free ferric aquo ion. The voltammetric and amperometric response of platinum comb-shaped interdigitated microelectrode array is decreased after fluoride addition. This decrease serves for the quantification of fluoride ions added to the solution. The detection limit of 4.5 × 10⁻⁵ mol dm⁻³ was achieved when one of the segments of interdigitated microelectrode array (IDA) was used as an indicating electrode. The detection limit is about one order of magnitude lower than in the case of conventional platinum macroelectrode. In comparison with ISE electrodes this method is faster and also avoiding large error resulting from the antilogarithmization of ISE Nerstian response. The method was applied to the analysis of toothpaste.