Enhanced voltammetric detection of estriol hormone using poly(l-arginine)-modified carbon nanotube paste as a responsive electrochemical sensor

The current research focused on designing a simple, inexpensive, and green electrochemical sensor for the sensitive estriol hormone (ETL) detection. To achieve this, a bare carbon nanotube paste electrode (BCNTPE) and electrochemically polymerized L-arginine (ARN)-modified carbon nanotube paste electrode (MCNTPE) were developed. The prepared electrochemical sensor was characterized using various techniques, such as field-emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV) methods. The investigation of the electrochemical oxidation nature of ETL in a supporting electrolyte of phosphate buffer solution (PBS) with pH 6.5 was carried out using a modified electrode (PARNMCNTPE) having superior electrocatalytic activity and more electrochemical active spots than the BCNTPE. Significant parameters like the impact of the pH of PBS, potential scan rate, and ETL concentration on the electrochemical behavior of ETL at the surface of the PARNMCNTPE were investigated. The potential scan rate and pH of PBS variation influence that the ETL oxidation at the PARNMCNTPE surface proceeded via pH-dependent and adsorption-controlled reaction pathways. The PARNMCNTPE senses ETL in the range from 2 × 10^–6 to 90 × 10^–6 M with a lower limit of detection (LOD) of 3.25 × 10^–7 M and a limit of quantification (LOQ) of 10.84 × 10^–7 M. The PARNMCNTPE shows decent stability, repeatability, and reproducibility for the detection of ETL. Additionally, the PARNMCNTPE analytical applicability was studied for ETL detection in medicinal samples. Graphical abstract: (Figure presented.)