Advantages of the incorporation of 2-hydroxyl propyl beta cyclodextrin and calixarene as ionophores in potentiometric ion-selective electrodes for rivastigmine with a kinetic study of its alkaline degradation

Three selective electrodes were investigated for rivastigmine (RIV). Sensor 1 was fabricated using ammonium reineckate (RNC) as a cation exchanger without incorporation of any ionophore. Sensors 2 and 3 used 2-hydroxy propyl β-cyclodextrin and 4-sulfocalix-8-arene as ionophores respectively in addition to RNC as a cation exchanger. Linear responses of RIV within the concentration ranges of 10−5 to 10−2, 10−6 to 10−2 and 5 × 10−7 to 10−2 M with Nernstian slopes of 51.5 ± 0.8, 54.6 ± 0.7 and 56.8 ± 0.4 mV/decade over the pH range of 4-7 were obtained using sensors 1, 2 and 3, respectively. The utility of ionophores had a significant influence on increasing the membrane sensitivity and selectivity of sensors 2 and 3 compared to sensor 1. The proposed sensors displayed useful analytical characteristics for the determination of RIV in pharmaceuticals, biological fluids and in the presence of its degradation product and thus could be used for stability-indicating assays. Sensor 3 was used to study the kinetics of RIV alkaline degradation that was found to follow a pseudo first-order reaction. The activation energy could be estimated from the Arrhenius plot to be 9.864 kcal mol−1.