Modification of polyvinyl chloride ion-selective membrane for nitrate ISFET sensors

Abstract

In this work, a Polyvinyl Chloride (PVC) ion-selective membrane was modified to detect nitrate based on Ion Selective Field Effect Transistor (ISFET) sensing technology in order to eliminate chloride interference. A modification was done with ethylenediamine solution to achieve animated PVC, which was then oxidized with sodium tungstate to form nitrone coated PVC membrane. The modified PVC was characterized using FTIR, 1H NMR, GPC, FE-SEM and EIS. The FTIR spectrum of animate PVC demonstrated -NH2 bending at 1580 cm−1, NO2 asymmetric stretching at 1650 cm−1 and NO out-of-plane deformation vibration at 837 cm−1. GPC analysis of the modified PVC showed that the PVC molecular weight was shifted to a high molecular weight. The PVC ion-selective membrane was immobilized on the ISFET to create nitrate sensors with the following characteristics. The Nitrate-Nitrogen detection limit is 1.20 ppm with linear range from 3−20 ppm at sensitivity of 56 ± 2 mV/dec. The sensor is useful for detecting small amount of nitrate in a mixed solution, which usually is the case in most situations. This sensor could be applied in many applications, such as agricultural industry, water reserve management and medical field as well.