Square wave voltammetric detection of 2,4,6-trinitrotoluene and 2,4-dinitrotoluene on a gold electrode modified with self-assembled monolayers

A rotating disc gold electrode, either bare or modified with an alkanethiol self-assembled monolayer, was used to measure the simultaneous square wave voltammetric differential current response of the electrochemical reduction of the two ordnance-related compounds (ORCs) 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT). On bare electrodes, background currents limited sensitivity to ppm levels. In order to suppress these interfering currents, the gold electrodes were modified with alkanethiols of various chain lengths, from 3 to 12 carbons, with hydrophilic (hydroxyl) or hydrophobic (methyl) end groups presented to the electrolyte. Gold electrodes endowed with hydroxyl-terminated monolayers enabled clear detection of TNT and DNT from mixtures of these two compounds. In addition, longer alkanethiols allowed extension of the working potential range to more negative values than achieved with shorter alkanethiols.