Hollow-fiber micro-extraction combined with HPLC for the determination of sitagliptin in urine samples

In this study, a three-phase, hollow-fiber, liquid-phase micro-extraction (HF-LPME) method coupled with high performance liquid chromatography was successfully developed for the determination of trace levels of the anti-diabetic drug sitagliptin (STG) in urine samples. Sitagliptin was extracted from 15 mL of the basic sample solution with a pH of 8.5 into an organic extracting solvent (n-octanol) impregnated in the pores of a hollow fiber and then back extracted into an acidified aqueous solution in the lumen of the hollow fiber with a pH of 3. After extraction, 20 mu L of the acceptor phase was injected into HPLC system. In order to obtain high extraction efficiency, the parameters affecting the HF-LPME, including pH of the source and receiving phases, type of organic phase, ionic strength, stirring rate, extraction time, the volume ratio of donor phase to acceptor phase and temperature, were studied and optimized. Under the optimized conditions, enrichment factors up to 88 were achieved and the relative standard deviation of the method was in the range from 3 to 6 %. The results indicated that the HF-LPME method has an excellent clean-up capacity and a high pre-concentration factor and could serve as a simple and sensitive method for monitoring the drug in urine samples.