Determination of Topiramate and Carbamazepine in Plasma by Combined Dispersive Liquid-Liquid Microextraction and Gas Chromatography-Mass Spectrometry

Dispersive liquid-liquid microextraction, an environmentally friendly extraction technique, followed by gas chromatography-mass spectrometry operating in selected ion monitoring (SIM) mode, is here presented for the simultaneous determination of two anticonvulsant drugs in plasma, Topiramate and Carbamazepine. Experimental parameters affecting the recovery of the proposed extraction method, such as the extraction and dispersion solvent, the extraction and dispersion volume, the sample amount, the pH of the aqueous phase, the ultrasound time, the centrifugation time and ionic strength, were investigated. The limits of detection for Topiramate and Carbamazepine were 0.01 and 0.025 mu g mL-1, and the limits of quantification were 0.025 mu g mL-1 and 0.05 mu g mL-1, respectively. The method is shown to be selective, accurate, precise and linear over the concentration ranges of 0.025-8 mu g mL-1 for Topiramate and 0.05-3 mu g mL-1 for Carbamazepine. The extraction recovery of the analytes ranged from 91.5% to 113.9%. The analytical method was successfully applied to real plasma samples received by the Forensic Toxicology Service of the Forensic Science Institute of Santiago de Compostela.