Potentiometric determination of the neurotransmitter acetylcholine with ion-selective electrodes containing oxatub[4]arenes as the ionophore

Modern liquid membrane based ion-selective electrodes (ISEs) require selective and lipophilic ionophores. For acetylcholine (ACh), an important neurotransmitter, there is still a lack of ionophores. We propose here a family of hydrophobic macrocycle Oxatub[4]arenes as ACh selective ionophores in potentiometric ISEs, which exhibited excellent stability, selectivity, and a lower detection limit of 100±20 nM. The stability constant of the acetylcholine-ionophore complex was determined to be (5.06±0.12) ×10⁵ M⁻¹ in PVC-NOPE membranes. The ACh ISEs were used to monitor the catalytic conversion of ACh to choline by the enzyme acetylcholinesterase. The concentration of ACh in mouse brain homogenate was also successfully measured. The proposed ionophores and ISEs are highly promising for continuous monitoring of ACh concentrations in complex biological samples.