Electrochemistry of dopamine at the polarised liquid|liquid interface facilitated by an homo-oxo-calix[3]arene ionophore

The homo-oxo-calix[3]arene-facilitated electrochemistry of dopamine at the polarised liquid|liquid interface is presented. Cyclic voltammetry indicated that the dopamine: homo-oxo-calix[3]arene complex formed at the interface between water and 1,2-dichloroethane had a 1:2 stoichiometry, which was confirmed by 1H NMR titration. The electrochemically-determined association constants for the homo-oxo-calix[3]arene complexes with dopamine (log β 8.3), Na+ (8.0) and K+ (7.5) showed that the ionophore was more selective for dopamine over the two alkali metal cations than the dibenzo-18-crown-6 ionophore. Square wave voltammetry was employed for assessment of low concentration measurements, with a limit of detection of 3.8 μM dopamine achieved. These results show that oxo-calixarene-based ionophores are useful reagents for the detection of dopamine at the interface between two immiscible electrolyte solutions.