Design of a stable solid-contact ion-selective electrode based on polyaniline nanoparticles as ion-to-electron transducer for application in process analytical technology as a real-time analyzer

• Novel use of SC-ISEs based on PANI nanoparticles as transducer layer in pharmaceutical analysis.
• The inclusion of PANI nanoparticles added more stability to the electrical signal due to their excellent electronic and chemical properties.
• The fast ion-to-electron transduction allows obtaining short response times.
• The hydrophobic behavior of PANI nanoparticles avoids the formation of thin water layers at the electrode/membrane interface.
• Good piece to piece reproducibility allow its future use as real-time analyzer in PAT applications.

Process Analytical Technology (PAT) is an essential step forward in the pharmaceutical industry. Real-time analyzers will provide timely data on quality properties. The aim of this work was to develop a junction between the pharmaceutical industry and recent advances in designing stable and reproducible solid-contact ion selective electrodes (SC-ISEs). Those sensors can be used as bench-top real-time analyzer for in-process tracking of the concentration of active pharmaceuticals. We have exploited the long-term stability of the chemically prepared polyaniline (PANI) nanoparticles to be applied as an ion-to-electron transducer layer between an ionophore-doped PVC membrane and glassy carbon electrodes. The inclusion of PANI nanoparticles added more stability to the electrical signal due to their excellent electronic and chemical properties. Moreover, the fast ion-to-electron transduction allows obtaining short response times and the hydrophobic behavior avoids the formation of water layers at the electrode/membrane interface. These results enabled the production of a series of SC-ISEs with improved piece-to-piece reproducibility where the potential was stable over 30 days with drift of 0.7 mV h−1. The electrodes were utilized for distigmine bromide determination as a model pharmaceutical drug; the linear range was 1.0 × 10−6–1.0 × 10−2 mol L−1 with a detection limit of 2.1 × 10−7 mol L−1.

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