Tetracaine – selective electrodes with polymer membranes and their application in pharmaceutical formulation control

Abstract

The construction and electrochemical response characteristics of poly(vinyl chloride) (PVC) membrane electrodes for tetracaine hydrochloride (TCH) are described. The sensing membranes incorporating ion-association complexes of tetracaine cation with phosphotungstic acid (PTA) or phosphomolybdic acid (PMA) or Sodium tetraphenyl borate (NaTPB) as electroactive materials and di-n-butyl phthalate (DBPH) or tri-n-butyl phosphate (TBP) as a plasticizer in PVC matrixes were evaluated. The results obtained show the electrodes based on PTA or PMA as electroactive compounds and DBPH as plasticizer with a fast, stable and near-Nernstian response over a wide concentration range (1 × 10⁻⁵–5 × 10⁻² M), with cationic slopes of 55.02 and 52.05 mV decade⁻¹ over a pH range of (2.5–6.5). The electrodes show good discrimination of tetracaine from several inorganic cations and sugars. The electrodes were successfully applied for the determination of tetracaine in pharmaceutical formulations.