In-situ surfactant-functionalized magnetic SBA-15 for the efficient extraction of cardiac glycosides in human plasma

A novel method of in-situ functionalized magnetic dispersive solid phase microextraction was established and coupled with high performance liquid chromatography-ultraviolet detection to determine four cardiac glycosides in human plasma. The adsorbent was prepared by in-situ functionalization of Fe₃O₄/SBA-15 with surfactant during the extraction process. The synthesized material was characterized using N₂ physisorption, infrared spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. Key parameters affecting extraction efficiency, including type of surfactant, concentration and volume of hexadecyl trimethyl ammonium bromide, adsorbent dosage, pH of sample solution, salt addition, extraction time, elution program, were systematically evaluated and optimized. The method demonstrated good linearity, satisfactory lower limit of quantification (deslanoside at 8.0 ng/mL, lanatoside C at 2.0 ng/mL, digoxin and digitoxin each at 1.6 ng/mL), high precision (RSD between 0.6% and 9.0%), good accuracy (RE within -8.8% to 11%), and acceptable extraction recoveries (56.1%-70.3%) under optimal conditions. Additionally, the method showed no significant matrix effect in human plasma, and the stability of the analytes was confirmed. The proposed method features simple and convenient adsorbent preparation and extraction processes, as well as high extraction efficiency for cardiac glycosides, making it a promising approach for trace analysis in complex matrices.