Study of the Ion Transfer of Quaternary Ammonium Ions by SWV

Simple transfer across the water/nitrobenzene interface of three model quaternary ammonium cations: Tetramethylammonium (TMA+), Choline (Ch+) and Tetrabutylammonium (TBA+), was followed by Square Wave Voltammetry (SWV) which constitutes a more sensitive approach to ionic quantification compared to other conventional techniques. A linear and reproducible response was observed in the range of 10 to 100 μM. Detection limits obtained by the ULA-2 method were 5.9, 10.7 and 13.8 μM for the mentioned ions, respectively. The simultaneous and independent analysis of two ions with different hydrophilic characters such as TBA+ and Ch+ is achieved by direct inspection of the resulting voltammograms after background subtraction. We report the particular effect of temperature in the SWV response studied in the range from 288 K to 313 K. The differential peak current shows a significant linear increase with increasing temperatures while background currents show no variation, thus turning the combined enhancement of using a differential pulse method at an optimal temperature into a significant option for quaternary ammonium ion quantitative analysis.