The Novel Three-Layer Electrode Based on Poly(Neutral Red) for Potentiometric Determination of Citrates

Abstract

The three-layer electrode consisting of the inner, middle, and outer layers of polythiophene (PTh), polyaniline (PANI), and poly(neutral red) (PNR), respectively, was developed, characterized, and tested as a potentiometric sensor for citrates. The spectroscopic and morphological findings based on Raman spectroscopy and scanning electron microscopy, respectively, demonstrated the consecutive formation of individual polymeric layers derived from PTh, PANI, and PNR in the multilayer system. The sharper and narrower peak profiles of PNR in the case of the three-layer system revealed a more organized structure than for the PNR layer alone. The PNR layer in such a novel arrangement shows the highest selectivity towards citrates among the tested carboxylates. Simultaneously, the unwanted influence of the underlying Pt surface is eliminated. The potentiometric characteristics of the proposed potentiometric sensor were examined at the detection of citrates in the real-world samples, compared with results for PNR simple electrode, and corresponded with the reference capillary electrophoresis and literature-based spectrophotometric method.