Hollow fiber liquid phase microextraction followed by high performance liquid chromatography for determination of some anti-dementia drugs in human plasma, urine and wastewater samples

Three-phase hollow fiber microextraction technique combined with high performance liquid chromatography-ultra violet (HPLC-UV) was applied for the extraction and determination of anti-dementia drugs rivastigmine and donepezil. In hollow fiber liquid phase microextraction (HF-LPME), the organic solvent is injected into the lumen of the porous hollow fiber, and the fiber acts as an interface between the sample solution and the extracting phase. Since very little amounts of the solvent are used, exposure of the operator to toxic organic solvents is minimized.[1] An important advantage of three-phase LPME is an excellent clean-up that enables the extraction of drugs and metabolites from biological matrixes and pollutants from the environmental samples with simultaneous clean-up of the extracts.[2] The target drugs were extracted from 10.0mL of aqueous solution with pH 12.0 (source phase) into an organic extracting solvent impregnated in the pores of a hollow fiber and finally back extracted into 40µL of acidic solution with pH 1 (receiving phase) located inside the lumen of the hollow fiber. The extraction was performed due to pH gradient between the inside and outside of the hollow fiber membrane. Different factors affecting the HF-LPME efficiency were studied and optimized. Under the optimum conditions (n-tetradecan) as membrane impregnation solvent, pHs of the source phase and receiving phase equal to 12.0 and 1, respectively, extraction time of 30 min, stirring speed of 1100rpm and 5% (w/v) NaCl for adjusting the ionic strength. Under the optimized conditions, enrichment factors up to 250 were achieved and the relative standard deviation (R.S.D.%) of the method was in the range of 4.6–9.3%. The calibration curves were obtained in the range of 4–1000 ng mL-1 with reasonable linearity (R2 0.994) and the limits of detection (LODs) ranged between 0.5 and 0.6 ng mL-1 (based on S/N = 3). Finally, the applicability of the proposed method was evaluated by extraction and determination of the drugs in urine, plasma and wastewater samples. The results indicated that hollow fiber microextraction method has excellent clean-up and high-preconcentration factor and can be served as a simple and sensitive method for monitoring of anti-dementia drugs in the biological samples.