Voltammetric behavior of ethopropazine and the influence of sodium dodecylsulfate on its accumulation on gold electrodes

Surfactants are sometimes used to improve the accumulation of some electroactive organic compounds, but anionic surfactants have seldom been utilized for such a purpose yet. In this paper, the influence of the anionic surfactant sodium dodecylsulfate (SDS) on the accumulation of ethopropazine (EPZ) at a polycrystalline gold electrode has been studied. EPZ exhibits an anodic peak at about 0.67 V (vs. SCE) and a shoulder in pH 3.5 citric acid–biphthalate buffer solution. In the absence of SDS, the peak is small and ill defined, but it becomes high and well shaped when SDS is added. This results from the adsorption of EPZ in the SDS membrane, which forms spontaneously on the gold electrode surface. For both cases EPZ shows the same electrode reaction mechanism, which is similar to that of promethazine (PMZ). The influence of other factors, such as pH value, variety and concentration of buffers, other surfactants, accumulation potential and time etc has been discussed. It was found that only the anionic surfactants had an enhancement effect on the EPZ accumulation. Also, the solution should be acidic or neutral so as to maintain the interaction due to its electrostatic nature. The optimum SDS concentration for EPZ accumulation is about 0.1 mM regardless of whether or not an accumulation potential is adopted. When all the experiment conditions are optimized, the peak current of the anodic peak changes linearly with the concentration of EPZ over the range 0.4–4 μM, and is thus of analytical significance.