Enhanced Electrochemical Sensing Platform Based on Mixed Oxide SiO2/Al2O3/Sb2O5 for Determination of Vitamin D3

Vitamin D is essential for health, and its quantification in supplements is important for immune support and disease prevention. The aim of this study was to develop an electrochemical sensor based on a glassy carbon electrode modified with the ternary oxide SiO 2 /Al 2 O 3 /Sb 2 O 5 for the determination of vitamin D3 in dietary supplements. The material was characterized by scanning electron microscopy, specific surface area analysis, and pore volume and diameter measurements. The analyses revealed spherical irregular particles, a high surface area of 339 m 2 g − 1 , a pore volume of 0.19 cm³ g − 1 , and an average pore diameter of 1.14 nm. These features enhance analyte adsorption and increase the electroactive area of the sensor. The electrochemical study, performed using cyclic voltammetry and differential pulse voltammetry, showed a shift in the oxidation potential of vitamin D 3 from +0.7 V (bare GCE) to +0.5 V with the modified electrode, along with a 65% increase in peak current, indicating a significant electrocatalytic effect. The sensor exhibited high selectivity and excellent sensitivity, with a detection limit of 0.12 µmol L − 1 and a linear range from 0.67 to 50.0 µmol L − 1 . Additionally, no significant interference from other fat‐soluble vitamins (A, E, and K) was observed. Therefore, the developed sensor proved to be effective for the trace‐level determination of vitamin D3 in commercial supplement samples.