Adsorptive Stripping Measurements of Chromium and Uranium at Iridium-Based Mercury Electrodes

Abstract

Iridium-based mercury electrodes are shown to be very suitable for adsorptive stripping measurements of chromium and uranium in the presence of the DTPA and propyl gallate complexing agents. The well-adhered mercury hemispherical electrode offers remarkable durability to withstand various manipulations expected under field deployment and the “pure” mercury surface essential for efficient adsorptive accumulation of the corresponding metal chelates. An electrochemical “cleaning” step ensures complete removal of the adsorbed metal chelate at the end of each run. The same hemispherical surface is thus used over a prolonged period of over five weeks, performing hundreds of runs with RSDs lower than 10%. Detection limits of 0.4 μg/L uranium and 0.5 μg/L chromium are obtained following a 10 min adsorptive accumulation. The electrode responds rapidly to the “switching” between solutions of low and high concentrations of chromium or uranium. Proper choice of the constant current used for stripping potentiometric m...