Portable multiple-channel ion-selective sensor

Spectrum-based sensors such as inductively coupled plasma optical emission spectroscopy (ICP-OES) and ion-selective sensors (ISS) are commonly used for ion concentration measurement. Compared with the spectrum-based method, ISS has the advantage of integrating multiple ion sensors and device package miniaturization. For this reason, ISS can be more portable than the spectrum-based sensor. In this study, we developed a portable multiple-channel ion-selective sensor with a detachable sensing probe where the electrodes are configured to potassium and nitrate sensors. This portable design aims to replace only the necessary sensor components, which are the ion-selective and reference electrodes. The conductive polymer used in this study are polyaniline (PANI) or poly(3-octylthiophene) (POT). The electrodes with and without conductive polymers between the ion-selective membranes and gold (Au) electrodes are evaluated. The sensitivity, internal resistance and capacitance are compared. Electrodes coated with PANI have lower resistance and higher conductivity. The capacitance of nitrate electrode, when coated with PANI, POT and without coating, are 149uF, 0.88uF and 1.1uF, respectively. Meanwhile, when coated with PANI, POT and without coating, the potassium electrode's capacitance is 108uF, 0.65uFand 1.22uF, respectively. The conductivity of nitrate and potassium electrodes coated with PANI are larger than 1.73 uF. The result suggests that polyaniline coating allows effective potential measurement, which minimizes the drifting <1mV/day) of the sensor's reading.