A metal-organic framework of type MIL-101(Cr) for emulsification-assisted micro-solid-phase extraction prior to UHPLC-MS/MS analysis of polar estrogens

A seamless two-step extraction procedure integrating ultrasound-assisted emulsification microextraction (USAEME) and vortex-assisted micro-solid-phase extraction (-SPE) was developed. A highly porous metal-organic framework of type MIL-101(Cr) is used as the sorbent, and ultra-high-performance liquid chromatography in combination with tandem mass spectrometry is used for detection. The steroid hormones estrone 17-estradiol, estriol, and 17-ethynylestradiol were extracted from water samples by using this method. These steroids are polar and do not pass through the polypropylene membrane that is conventionally used in -SPE. In the method presented here, 1-octanol is used in USAEME to extract and pre-concentrate the steroids. This facilitates the transfer to the MIL-101(Cr) phase retained by the membrane in the subsequent -SPE step. MIL-101(Cr) was characterized by various methods, and the parameters affecting the overall extraction efficiency were optimized. Under the most favorable conditions, the limits of detection are between 0.95 and 23ngL(-1). Good intra-day and inter-day precisions were obtained, with relative standard deviations of 9.9%. Enrichment factors are between 34 and 52. The method was applied to genuine environmental water samples in which estrone was detected. Relative recoveries ranged between 85.4% and 120.8%.