Ionic Liquid-Based Dispersive Liquid-Liquid Microextraction Coupled with Capillary Electrophoresis to Determine Drugs of Abuse in Urine

A novel method for dispersive liquid-liquid microextraction using ionic-liquid was applied for pre-concentration, separation and simultaneous detection of trace-amount ephedrine and ketamine drugs in urine samples by coupling with high performance capillary electrophoresis. Various experimental conditions, including selection of ionic-liquid and dispersant and their concentrations, the amount of addition of NaOH and HCl in the sample, were investigated and optimized. The pretreated sample (0.5 mL) was added into 3.5 mL 0.2 g L−1 NaOH solution and its extraction was performed within several seconds by using 40 mL [BMIM]PF6 as extraction solvent and 350 mL acetonitrile as dispersant, then the analytes were back-extracted into 60 μL 0.1 M HCl solution. Under the optimum conditions, the good linearity was achieved for detection of ephedrine and ketamine in the range of 0.10–10 μg mL−1 (R2 is 0.9968 for ephedrine and 0.9981 for ketamine). The enrichment factors for ephedrine and ketamine were 28.8 and 16.9, and the LODs were 0.015 and 0.03 μg mL−1, respectively. (S/N = 3). The good repeatability was obtained with RSD less than 6.8% (n = 6). The feasibility of the present method was demonstrated by successful determination of ephedrine and ketamine in urine samples, with spiked recoveries in the range of 79%–90% and LODs (S/N = 3) of 0.21 μg mL−1 for ephedrine and 0.39 μg mL−1 for ketamine. The method has properties such as cheap, easy-to-operate, high enrichment efficiency and detection sensitivity and less interference, and would have valuable potential application in detection of trace-amount drugs in the biological samples.