Sub-monolayer assemblies of octanethiol and octadecylthiol at gold electrodes for the direct analysis of 4,4′-oxydianiline in wastewaters and shoe-dyeing samples

Self-assembled monolayers (SAMs) of di-n-octadecyldisulphide (C18) and n-octanethiol (C8) were prepared on gold electrodes. From the studies carried out by cyclic voltammetry and square wave voltammetry, it was observed that the electrochemical behaviour of 4,4′-oxydianiline on these electrodes is affected by the length chain of the alkanethiol. After the optimization of all the variables involved in the electrochemical response of 4,4′-oxydianiline by square wave voltammetry employing the modified electrodes, it is possible the determination of 4,4′-oxydianiline with a detection limit of 0.04 μg/mL (C18) and 0.06 μg/mL (C8) and determination limits of 0.12 and 0.22 μg/mL, respectively. The calculated Er (%)n=10 and R.S.D.(%)n=10 values were minor than 2.2% and 3.7%. The proposed methods were successfully applied to the analysis of oxydianiline in wastewater and shoe-dyeing samples.