Electrochemical sensing of doxepin using acylthiourea-modified glassy carbon electrode

Acylthiourea (ATU) compounds 4-(3-(furan-2-carbonyl)thioureido)benzoic acid (1), 4-(3-(thiophene-2-carbonyl)thioureido)benzoic acid (2), and 4-(3-(benzoyl)thioureido)benzoic acid (3) were synthesized and characterized by NMR (H-1 and C-13), FT-IR, UV-Vis and mass spectrometry. The molecular structures of compounds 1 and 2 were confirmed by single crystal X-ray diffraction studies. An electrochemical method employing Nafion (Nf)-ATU (1-3)-multi-walled carbon nanotubes (MWCNTs)-modified glassy carbon (GC) electrode (Nf/ATU/MWCNTs/GC) has been developed for the determination of DHCl. Electrochemical studies were carried out in phosphate buffer by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DHCl was detected at 1.1 V vs Ag/AgCl (3 M KCl). The proposed sensor for the determination of DHCl was investigated with three acylthiourea derivatives (1, 2, and 3) under optimized experimental conditions using blood plasma samples. The lowest detection limit toward DHCl was 0.09 mM.