Potentiometric Sensors Based on Nafion Membranes Modified by PEDOT for Determining Procaine, Lidocaine, and Bupivacaine in Aqueous Solutions and Pharmaceuticals

Hybrid materials based on perfluorinated sulfonic acid Nafion-type membranes and poly-3,4-ethylenedioxythiophene (PEDOT) with a gradient distribution of the latter along the film length were synthesized by in situ oxidative polymerization. The initial monomer concentration (0.01 and 0.002 M) and the concentration ratio of the monomer to the oxidant (1/1.25 and 1/2.5) were varied. We studied the effect of the equilibrium and transport properties of the obtained materials on the characteristics of cross-sensitive DP-sensors (analytical signal is the Donnan potential) in aqueous solutions of procaine, lidocaine, and bupivacaine hydrochlorides, including those containing sodium chloride, in a concentration range from 1.0 × 10–4 to 1.0 × 10–2 M and pH from 2 to 6. The relative error in determining the active substance in the Novokain preparation using a DP-sensor based on the Nafion/PEDOT membrane (0.002 M, 1/2.5) was 0.4%. An array of DP-sensors based on Nafion and Nafion/PEDOT (0.002 M, 1/1.25) membranes was used to determine bupivacaine hydrochloride and sodium chloride in the Markain® Spinal preparation with an error of 11 and 6%, respectively.