Epoxy-based all-solid-state poly(vinyl chloride) matrix membrane calcium ion-selective microelectrodes

Abstract

Calcium ion-selective microelectrodes have been constructed from PVC matrix membranes containing a calcium bis{di[4-(1,1,3,3-tetramethylbutyl)phenyl]phosphate} electroactive component with dioctyl phenylphosphonate, tripentyl phosphate or trioctyl phosphate as a plasticising solvent mediator, and from the Philips IS 561/SP membrane. The electrode membranes are backed with a silver-based conductive epoxy implanted with a copper wire for electrical contact. Of the three types of electrodes designed, namely, glass capillaries with a pre-formed membrane (type A) or an applied membrane (type B) and infrared heat-drawn Perspex capillaries with applied membrane (type C), the most functional are types B and C, which have functional lifetimes of 6 and 10 d, respectively.The electrodes have tip diameters of 1–3 µm for glass and 5–10 µm for Perspex, the bevelled tip in the latter ensuring a sharp edge.