Development of a Magnetic Solid-Phase Extraction Sorbent for Enhanced UV-Vis Spectrophotometric Detection of Riboflavin in Vitamin Tablets

A UV-Vis spectrophotometric method was developed for the determination of riboflavin (Vitamin B2), employing magnetic solid-phase extraction (MSPE) for preconcentration. A novel magnetic material (Fe₃O₄@TEOS-Captopril) was synthesized for this purpose and characterized using Fourier-Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). All parameters affecting the MSPE efficiency, such as sample pH, contact time, and elution conditions, were optimized. The determination of the preconcentrated riboflavin was carried out using a UV-Vis spectrophotometer at three characteristic wavelengths: 268, 370, and 446 nm. The absorbance at 446 nm consistently provided the highest signal intensity and was therefore selected for all quantitative analyses to maximize sensitivity. Under the optimized conditions at this wavelength, the method exhibited a linear range of 125.00–2500.00 ng mL⁻¹. The limit of detection (LOD) and limit of quantification (LOQ) were calculated as 37.88 ng mL⁻¹ and 113.64 ng mL⁻¹, respectively. The method's accuracy and robustness against matrix effects were evaluated through recovery studies via the standard addition method on commercial pharmaceutical tablet samples, yielding satisfactory results between 93.7% and 100.4%. The overall procedure was evaluated using the Blue Applicability Grade Index (BAGI), achieving a score of 65. This score reflects a favorable balance, confirming the method's robustness against matrix effects and its relatively green profile, facilitated by the magnetic solid-phase extraction which reduces solvent consumption.