Separation and enrichment of fingolimod and citalopram active drug ingredients by fabric phase sorptive extraction followed by high performance liquid chromatographic analysis with diode array detection.

Multiple Sclerosis (MS) is a chronic disorder affecting the central nervous system. The treatment of MS often involves a combination of pharmaceutical agents, including Fingolimod (FIN) and Citalopram (CIT). The analysis of these drug compounds plays a crucial role in various stages of health sciences, ranging from drug development to therapeutic monitoring. In this study, a rapid and sensitive analytical method was developed for the trace determination of FIN and CIT using fabric phase sorptive extraction (FPSE) as a sample pretreatment technique, followed by high-performance liquid chromatography coupled with diode array detection (HPLC-DAD). Key FPSE parameters-including pH, adsorption and desorption conditions, and extraction time-were systematically optimized. Analytical performance characteristics of the proposed method were evaluated under optimized conditions in accordance with international guidelines. Chromatographic separation of FIN and CIT was achieved via isocratic elution using a mobile phase composed of acetonitrile, pH 3.0 phosphate buffer, and methanol (50:40:10, v/v/v) at a flow rate of 1.0 mL min. The limits of detection (LOD) for FIN and CIT were determined to be 7.46 ng mL and 5.97 ng mL, respectively. The method demonstrated good precision, with relative standard deviation (RSD) values below 6.0 % for spiked samples. Recovery rates from synthetic urine and saliva matrices ranged between 93.1 % and 105.0 % for both analytes, confirming the method's accuracy and applicability to biological samples.