The influence of acid-base properties of dopants incorporated into the MF-4SC membranes on the characteristics of potentiometric sensors in nicotinic acid solutions
Nicotinic acid (3-pyridinecarboxylic acid) is a B vitamin, and it is a pollutant with respect to the environment. Mass spectrometry and chromatography techniques with various detection methods, as well as electrochemical sensors are known for its determination in food, pharmaceutical and physiological environments. A variety of hybrid materials are used in voltammetry sensors for the determination of nicotinic acid. However, the use of such materials in potentiometric sensors for determining nicotinic acid is not described in the literature. In this work, the possibility of using of hybrid materials based on the perfluorosulfonic acid cation exchange MF-4SC membrane and surface-modified nanoparticles of zirconia and silica for potentiometric determination of nicotinic acid in aqueous solutions was investigated. It was shown that varying the acid-base properties and the volume fraction of the dopants incorporated into the membrane have a significant effect on the cross sensitivity of DP-sensors (sensors with Donnan potential as analytical signal) to nicotinic acid and hydroxonium ions. The presence of 3 wt.% silica with 15 mol.% 3-aminopropyl on the surface in the membrane reduces the sensitivity of DP-sensors to interfering hydroxonium ions by 2 times and the detection limits of nicotinic acid by 6 times compared to those for an unmodified sample. Also, a decrease in the interfering effect of hydroxonium ions on the response of the DP-sensor and a decrease in the detection limit of nicotinic acid are achieved by using a membrane containing 5 wt.% silica with 3-propyl sulfonic acid groups. DP-sensors based on selected membranes are characterized by a high sensitivity to nicotinic acid (30.8 and 29.3 mV/pc). These samples can be used to develop sensory systems for determination nicotinic acid in aqueous solutions and pharmaceuticals.