A New Way to Use Hydrophobic Deep Eutectic Solvents: Improved Lead Detection Using an Ion-Selective Electrode with a...

In this study, the use of terpene-based hydrophobic deep eutectic solvents (HDESs) in the preparation of polymeric membrane ion-selective electrodes is presented. HDES obtained from terpenes (menthol and thymol) and octanoic acid are used as a new component of polymeric membrane of potentiometric sensors sensitive to lead ions. Electrodes containing different amounts of HDES in the membrane (from 1 to 12 % wt./wt.) are prepared, and potentiometric measurements are carried out for these electrodes to determine the detection limit, the slope of the characteristic, and the response linear range. Based on the analysis of electrode performance, it is found that the optimum concentration of HDES in the membrane is 5 wt%. For such membranes, a more detailed study is carried out using a solid contact sensor. Selectivity toward interfering species as well as potential stability and reversibility, optimum pH range, effect of light, and presence of gases in the sample solution are investigated for such sensors. The obtained measurement results indicate that the tested sensor containing HDES in the membrane has good analytical parameters, and excellent selectivity (log K ≤ -4.4). It has been successfully used to determine lead in real environmental water samples after a brief pretreatment with XAD-7 resin.