A novel hybrid organic–inorganic silsesquioxane and cobalt(ii) tetrasulphophthalocyanine material as an efficient electrochemical sensor for the simultaneous determination of the anti-hypertensive nifedipine and its metabolite

Abstract

In this study, a novel ionic silsesquioxane (Si4DMAP⁺Cl⁻) was developed through a facile synthetic sol–gel method and utilized as a recoating layer with the cobalt(II) tetrassulphophthalocyanine (CoTsPc) compound in order to modify a glassy carbon electrode (GCE) substrate. The silsesquioxane material was characterized using ²⁹Si and ¹³C NMR, FTIR, TGA, fluorescence and UV-Vis spectroscopic techniques. Additionally, the GCE/CoTsPc–Si4DMAP⁺Cl⁻ electrode platform was applied as an electrochemical sensor for the determination of nifedipine (NIF), an anti-hypertensive drug, and its main metabolite, dehydronifedipine (dHNIF). DFT calculations were also performed to evaluate the redox properties of NIF and dHNIF. Individual and simultaneous determinations of NIF and dHNIF were performed in the range of 0.015–1.75 μmol L⁻¹ using optimized supporting electrolyte conditions and stripping differential pulse voltammetry as an analytical tool. The limit of detection (LoD) values for both analytes were 6.2 nmol L⁻¹ for NIF and 4.5 nmol L⁻¹ for dHNIF, respectively. The proposed method was applied for the determination of NIF and dHNIF in synthetic urine and serum samples with a recovery range between 101–110% (n = 3). The GCE/CoTsPc–Si4DMAP⁺Cl⁻ electrode platform is presented here as a biomedical testing tool considering therapy-resistant conditions of hypertensive patients.