Coulometric back titration based on all-solid-state electrodes for phenylephrine hydrochloride determination

Existing coulometric titration generally used liquid reference electrodes, with limitations of frequent maintenance and liquid leakage risk and requiring vertical working position. Herein, we proposed an all-solid coulometric titration based on the glassy carbon electrode (GCE) and preliminarily utilized it in phenylephrine hydrochloride (PHE) analysis with a universal back titration program. Subsequently, the long-term stability of the GCE in bromine and iodine solution was evaluated comprehensively by electrochemical characterization and titration measurement. The results presented an excellent linear relationship between electrolysis time and PHE concentration from 0.3 to 20 mM, with a limit of detection of 0.07 mM (3 S₀/S). It also showed an excellent standard recovery rate and a short testing time within 10 min. Compared with bromometry in the pharmacopoeia, the all-solid coulometric titration exhibited higher accuracy and precision in formulation detection with simpler operation. The long-term stability experiments indicated that the potential difference mutation was unaffected by the electrochemical property of the GCE. Conclusively, this enabling work provided an all-solid coulometric titration for drug determination without maintenance in the long term and contributed to its further integration and industrialization.