Study of phenomena related to the fabrication and function of glass nanopore ion-selective electrodes

The development and study of ion-selective electrodes (ISE) with microscopic internal volumes are presented. The specific aim of this research is to characterize the behavior associated with ISE function when the internal volume is microscopic (0.5 to 5 pL). The techniques and methods associated with the fabrication of such devices are also presented. In Chapter 2, phenomena associated with the fabrication and responses of glass nanopore ion-selective electrodes (GNISE) are studied. The dimensions of the microscopic internal components are determined using microscopy and cyclic voltammetry. The Ag/AgCI internal reference electrode is unstable because the current drawn by the voltage-measuring device oxidizes or reduces the reference. AgCI dissolution also contributes to the problem. A AgCI saturated solution and an electrometer with a 200 TQ impedance allow a stable measurement for at least 1 h. K+ GNISEs behave reproducibly for at least 4 weeks. Their sensitivity is 57 +/-1.3 mV/Log aK+ with a lower detection limit of 6 +/- 5.7 x 10"6 M. The lower detection limit of a C a 2 + GNISE is decreased 3 orders of magnitude lower than the detection limit of a commercial Ca2 + ISE. The membrane volume is reduced to subpicoliter values, and dissolves in less than 2 days unless the membrane is sufficiently hydrophobic.