M.V. Sangaranarayanan

In recent years, there has been significant interest in the design of electrodes for enhanced electrochemical sensing platforms towards selective and sensitive detection of biological steroid hormones. We report here a facile, template-free electrodeposition of tin nanorods on glassy carbon electrodes and analyse its efficacy for the sensing of progesterone using voltammetric and amperometric techniques. The physicochemical properties of the tin-nanorods modified glassy carbon electrodes are characterized by electron microscopic studies, UV–vis spectral analysis, X-ray diffraction and electrochemical impedance spectroscopy. The mechanism involved in the reduction of progesterone has been elucidated using quantum chemical calculations and the influence of the cationic surfactant (cetyltrimethylammonium bromide) is pointed out. The estimation of progesterone is carried out with differential pulse voltammetry and amperometry. The electrode exhibits an impressive response towards the sensing of progesterone in terms of higher sensitivity, linear calibration regime varying from 40 to 600 μM with the lowest detection limit being 0.12 μM. The effect of other interfering agents such as testosterone, 17β-estradiol, creatinine, uric acid and ascorbic acid is also analysed using differential pulse voltammetry. The analysis of progesterone assay in commercial pharmaceutical formulations has also been carried out and reveals a satisfactory agreement.

The electrochemical behaviour of thyroxine (T4) is analysed using the disposable screen-printed carbon electrode (SPCE) in the neutral phosphate buffer solution with cyclic voltammetric technique. The Differential Pulse Voltammetry and Chronoamperometry were employed for sensing of T4. The lowest detection limit of 3nM was obtained from the differential pulse voltammetric method without preconditioning. The Density Functional Theoretical study of T4 was performed to elucidate the mechanism of oxidation. The analysis of the commercial pharmaceutical samples indicates the validity of the proposed method.