Kinetic-photometric monitoring of the formation of MnO2 nanoparticles and their application to the determination of iodide

We describe a method for kinetic-spectrophotometric monitoring of the formation of MnO₂ nanoparticles (NPs) by reduction of permanganate ion. Iodide was selected as a model analyte. The NPs were characterized by atomic force microscopy, transmission electron microscopy, powder x-ray diffraction, energy-dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy and nitrogen physisorption surface area analysis. The change in absorbance at 415 nm over time serves as the analytical signal, and experimental variables that affect the slope have been studied. The slope is linearly related to iodide concentrations in the range from 0.2 to 3 μg⋅mL‾¹, and the limits of detection and quantification are 0.05 and 0.17 μg⋅mL‾¹, respectively. The intraday and interday precision (given as relative standard deviations for n = 5) are 1.4 and 3 %, respectively. The method has been successfully applied to the determination of iodide in a pharmaceutical product. In our perception, this is the first model where the monitoring of the early stages of the formation of NPs has been exploited as analytical signal.