Electrochemical detection of hydrochlorothiazide in the prescence of amlodipine and valsartan using FeMOF/g-C3N5−Modified Carbon Paste Electrode

Abstract

A novel electrochemical sensor based on a carbon paste electrode (CPE) modified with nitrogen-doped graphitic carbon nitride and an iron-based metal-organic framework (FeMOF/g-C₃N₅) was developed for the sensitive detection of hydrochlorothiazide (HCTZ). The synthesized FeMOF/g-C₃N₅ nanocomposite was characterized using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), which confirmed its successful synthesis and structural integrity. Electrochemical characterization through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated significantly enhanced electron transfer properties, reducing the charge transfer resistance from 8865 Ω (bare CPE) to 517 Ω and increasing the peak current from 9.59 μA cm⁻² to 61.17 μA cm⁻². Under optimized conditions (PBS 0.1 M, pH 7.0, scan rate of 0.1 V/s, 250 mV modulation amplitude, 25 mV step potential), the sensor showed a linear response to HCTZ over two ranges: 0.005–0.7 µM and 5.00–100.0 µM, with a detection limit of 1.30 nM and a sensitivity of 41.475 μA/μM. Chronoamperometric analysis indicated an irreversible diffusion-controlled process with a diffusion coefficient of 2.4 × 10⁻⁵ cm²/s. The sensor exhibited excellent selectivity, enabling the simultaneous determination of HCTZ, amlodipine, and valsartan, with well-separated signals. Recovery studies in pharmaceutical tablets, human plasma, and urine samples yielded values between 93.33 % and 110 %, confirming the accuracy of the method for complex matrices. The synergistic integration of FeMOF and g-C₃N₅ provides a high-performance sensing interface, offering a cost-effective and sensitive approach for the electrochemical detection of HCTZ in clinical and pharmaceutical applications.