# A New Way to Use Hydrophobic Deep Eutectic Solvents: Improved Lead Detection Using an Ion‐Selective Electrode with a Polymer Membrane Modified by them

## TL;DR

This paper introduces a new method for detecting lead using a sensor modified with hydrophobic deep eutectic solvents, which improves detection accuracy and selectivity.

## Contribution

The first use of terpene-based hydrophobic deep eutectic solvents in lead-sensitive ion-selective electrodes is demonstrated.

## Key findings

- Electrodes with 5 wt% HDES in the membrane showed optimal performance with a detection limit and excellent selectivity (log K ≤ −4.4).
- The sensor successfully detected lead in real environmental water samples after pretreatment with XAD-7 resin.
- The HDES-modified membrane improved sensor stability, reversibility, and resistance to interfering species.

## Abstract

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.

First use of hydrophobic deep eutectic solvents (HDESs) in the preparation of polymeric membrane lead‐sensitive ion‐selective electrodes is presented. It is found that enrichment of the membrane with HDES additive improves the electrode's parameters, primarily lowering the detection limit and increasing selectivity. The proposed electrodehas been successfully used to the analyse real samples.© 2025 WILEY‐VCH GmbH