Metal organic framework/chitosan/polyethylene oxide composite columnar foam as a sorbent for the enrichment and determination of estrogens in environmental aqueous solutions

Abstract

In this work, a metal organic framework/chitosan/polyethylene oxide composite MIL-53(Al)/CS/PEO columnar foam was successfully designed and fabricated, in which polyethylene oxide (PEO) was applied to serve as a porogen to improve the MOF loading capacity of the MIL-53(Al)/CS/PEO foam. The inherent characteristics, e.g. mechanical strength and stability of the modified foams, were also significantly improved. The MIL-53(Al)/CS/PEO columnar foam was chosen as a sorbent to develop a vortex-assisted solid phase extraction (VA-SPE) for the first time. The adsorption performance of the MIL-53(Al)/CS/PEO columnar foam was measured by choosing two typical estrogens as models to discuss the adsorption behavior. The maximum adsorption capacities of estradiol (E2) and ethinyloestradiol (EE2) are 75.2 and 42.0 μg g⁻¹, respectively. The efficient method was then successfully applied for the extraction of trace levels of four estrogens (estrone, estradiol, estriol and ethinyloestradiol) in bulk volume environmental water, followed by high-performance liquid chromatography-fluorescence detection (HPLC-FLD). Satisfactory results of the methodology validation were obtained. Under the optimum conditions, the linear ranges were 0.02 to 40 μg L⁻¹ with a coefficient of determination (R²) from 0.9953 to 0.9996. The method showed a lower limit of detection in the range of 0.3–6.6 ng L⁻¹. In addition, the recoveries ranged from 73.5% to 116.7% with relative standard deviations smaller than 8.6%. The proposed columnar foam was durable, and the method employed was simple and environmentally friendly. Moreover, the foam can maintain its adsorption ability after recycling several times. The novel method proposed in this work could provide a simple and efficient sample preparation and has great application potential for sample pretreatment in a bulk mass aqueous sample.