Development of a robust, fast screening method for the potentiometric determination of iodide in urine and salt samples

In this work, a potentiometric flow injection method is described for the fast bi-parametric determination of iodide and iodate in urine and salt samples. The developed methodology aimed for iodine speciation with a potentially portable system (running on batteries). The iodate reduction to iodide was effectively attained in line within the same manifold. The iodide determination was accomplished in the dynamic range of 2.50×10⁻⁶–1.00×10⁻³ M and the total iodine dynamic range, resulted from iodide plus iodate, was 3.50×10⁻⁶–2.00×10⁻³ M. The calculated limits of detection were 1.39×10⁻⁶ M and 1.77×10⁻⁶ M for iodide and iodate, respectively. A determination rate of 21 h⁻¹ for the bi-parametric iodide and iodate determination was obtained for sample injection. The urine samples (RSD <5.8% for iodide and RSD <7.0% for iodate) results were in agreement with those obtained by the classic Sandell-Kolthoff reaction colorimetric reference procedure (RD <7.0%) and standard samples from Centers for Disease Control and Prevention, Atlanta, USA (CDC) international inter-laboratory EQUIP program. The developed flow method was also successfully applied to the iodide and iodate determination in salt samples (RSD <3.1% for iodate and iodide), with comparable results to conventional procedures. No significant interferences were observed interference percentage <9% for both determinations.