A tripodal ammonium ionophore with improved selectivity and lipophilicity for potentiometric detection of ammonium ions in whole blood

Ammonium ions (NH 4 + ) are important in agriculture, biochemical diagnostics, the understanding of the nitrogen cycle in aquatic systems and enzyme reaction products of biosensors. Ion-selective electrodes (ISEs) are among the most widely employed methods for NH 4 + determination. Their the sensitivity and selectivity are crucial performance factors that are largely governed by the properties of the ionophore. In this work, we report on a new ammonium ionophore, 1,1′,1″-((2,4,6-trihexylbenzene-1,3,5-triyl)tris(methylene))tris(1H-pyrazole), a 6-fold substituted tripodal benzene derivative. Thin-membrane ion transfer voltammetry was used to characterize the fundamental properties of the ionophore, including the response to NH 4 + , ion selectivity, and binding stoichiometry. The ionophore exhibits superior selectivity for NH 4 + over K + ( log K NH 4 + , K + pot = − 2.00 ± 0.02 ) and is found to form 1:1 complexes with ammonium. It outperforms most previously reported ionophores including nonactin. Potentiometric measurements in undiluted whole blood further demonstrated its long-term stability and applicability in real sample analysis.