Fabrication of Liquid-Contact Polymeric Membrane Ion-Selective Microelectrodes with a Long Lifetime

The lifetime of polymeric membrane ion-selective microelectrodes is one of the key factors limiting their practical applications. Herein, we report a simple strategy for the fabrication of liquid-contact ion-selective microelectrodes with a long lifetime by increasing the thickness of the polymeric sensing membrane via filling the membrane solution from the back of the micropipette tip. A lead ion-selective microelectrode (Pb²⁺-ISμE) was used as a model sensor. The geometry of the electrode tip and the amount of membrane solution were optimized. The microelectrode exhibited a Nernstian response slope of 27.4 ± 0.7 mV decade^-1 over the concentration range from 1.0 × 10^-7 to 1.0 × 10^-3 M with a detection limit of 4.2 × 10^-8 M. Notably, the response slope of the microelectrode decreased by only 2.2% in 30 days.