Carbonaceous materials-based aloe vera leaf waste as magnetic adsorbents for pre-concentration selective serotonin reuptake inhibitor antidepressant drugs from aqueous solutions

This study successfully synthesized, characterized, and applied magnetic activated carbon derived from aloe vera leaf waste and modified with an alkaline activator for the pre-concentration of selective serotonin reuptake inhibitor antidepressant drugs (escitalopram, fluoxetine, paroxetine) in water. A range of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), specific surface area analysis, and Fourier transform infrared spectroscopy (FTIR), were employed to investigate the physical and chemical properties of the synthesized materials. Response surface methodology, specifically Plackett-Burman and Central Composite Design, was utilized to explore synergistic factors influencing the magnetic solid-phase extraction method. The optimal conditions for pre-concentrating the target analytes were determined to be a sample volume of 15 mL, a water temperature of 23 °C, 1 g of activated carbon, a stirring speed of 400 rpm, and a pH of 9.0. Under these conditions, a high recovery of 90 % was achieved, with a desirability value of 0.90. Quantification of the analytes was performed using high-performance liquid chromatography equipped with a diode array detector. The method demonstrated low limits of detection and quantification, ranging from 0.35 to 1.83 ng/mL and 1.15 to 6.73 ng/mL, respectively. Extraction recoveries at three spiked concentration levels varied from 72 % to 92 %, while intra- and inter-day precision exhibited low bias, with relative standard deviations (RSDs) below 10 %. Regeneration studies revealed recovery losses of <10 % after four cycles of use. Freundlich isotherm (R² >0.992) and pseudo second order kinetic (R² >0.980) models were best fitted with experimental results. Furthermore, the magnetic dispersive micro solid-phase extraction method proved to be environmentally sustainable, achieving an overall AGREEnness score of 0.68, a Blue Applicability Grade Index of 65.0, and a Sample Preparation Metric Sustainability score of 7.26, highlighting its green credentials.