Adsorption and selective recognition of 17ß-estradiol by molecularly imprinted polymers

Benzoyl isothiocyanate modified surface of silica gel as the extraction material for adsorbing steroid hormones in water

Steroid hormones have been listed as priority pollutants in the environment, and their detection and pollution control deserve our extensive attention. In this study, a modified silica gel adsorbent material was synthesized by benzoyl isothiocyanate reaction with hydroxyl groups on the silica gel surface. The modified silica gel was used as a solid phase extraction filler for the extraction of steroid hormones from water, which was further analyzed by the HPLC-MS/MS method. The FT-IR, TGA, XPS, and SEM analysis indicated that benzoyl isothiocyanate was successfully grafted on the surface of silica gel to form a bond with an isothioamide group and benzene ring as the tail chain. The modified silica gel synthesized at 40 °C showed excellent adsorption and recovery rates for three steroid hormones in water. Methanol at pH 9.0 was selected as the optimal eluent. The adsorption capacity of the modified silica gel for epiandrosterone, progesterone, and megestrol acetate was 6822 ng mg^-1, 13 899 ng mg^-1, and 14 301 ng mg^-1, respectively. Under optimal conditions, the limit of detection (LOD) and limit of quantification (LOQ) for 3 steroid hormones by modified silica gel extraction with HPLC-MS/MS detection were 0.02-0.88 μg L^-1 and 0.06-2.22 μg L^-1, respectively. The recovery rate of epiandrosterone, progesterone, and megestrol was between 53.7% and 82.9%, respectively. The modified silica gel has been successfully used to analyze steroid hormones in wastewater and surface water.

Molecularly Imprinted Polymers and Magnetic Molecularly Imprinted Polymers for Selective Determination of Estrogens in Water by ESI-MS/FAPA-MS

Qualitative and quantitative analysis of estrogens content in natural water is a difficult task. An important problem in the analysis of hormones in water is the quantitative determination of their individual species. Low detection limits and instability of estrogen derivatives are the main challenges. Magnetic molecularly imprinted polymers (mag-MIPs) in combination with Flowing Atmospheric-Pressure Afterglow Mass Spectrometry (FAPA-MS) were successfully used for analysis of estrogen hormones in water samples. The aim of the study was to obtain mag-MIPs selective to estrone (E1) and β-estradiol (E2) for solid phase extraction and pre-concentration of estrogens. Due to their superior analyte binding properties at low concentrations (0.03 g in 1 g of polymer structure) and possibility of magnetic separation, mag-MIPs were proven to be very convenient and efficient adsorbent materials. In addition, MS analyses were performed using two ionization sources: ESI- and FAPA-MS. For both estrogens, LOD was significantly lower for FAPA-MS analysis (0.135 μg L⁻¹ for E1 and E2) than for ESI-MS analysis (27 μg L⁻¹ for E1 and 13.6 μg L⁻¹ for E2). The total estrogen concentration in the environmental water sample was determined as: cE1 = 0.271 μg L⁻¹ and cE2 = 0.275 μg L⁻¹.

Assessment of molecularly imprinted polymers as phosphate sorbents

Phosphorus (P) is a non-renewable natural resource which is used extensively in agriculture as a fertilizer. Phosphate (PO₄^3-) rocks are mined to meet growing agricultural demands induced by rising global populations. Much of the P used in agricultural fields finds its way into surface waters where it permanently resides, leading to devastating effects on the aquatic ecosystem through eutrophication of the waterbodies. This research was aimed at developing a sorbent that can engender a P reuse cycle by utilizing eutrophic surface waters as viable P sources (mines). The goal was to develop a sorbent which can selectively recover low concentration (≤100 P μg L^-1) typical of eutrophic waters. Molecularly imprinted polymers (MIPs) were identified as a potential technology for accomplishing this goal. Three MIPs were screened for viability by assessing their sorption capacities. After the initial screening, one MIP was selected for further studies. The selected MIP was found to have partial PO₄^3- selectivity and tunable P sorption capacity. Adjusting the template:monomer ratio resulted in an increase in P sorption capacity from ∼11 to ∼28 mg PO₄^3--P g^-1, making this MIP competitive with existing technologies. The MIP was characterized to understand the polymer chemistry and mechanisms of P-removal. The possible mechanisms of aqueous P removal by the MIP were identified as selective chemical binding to the imprinted recognition sites and electrostatic attraction.

Molecularly imprinted polymers for selective adsorption of quinoline: theoretical and experimental studies

The effects of solvent on the synthesis of molecularly imprinted polymers (MIPs) for the selective adsorption of quinoline were evaluated in this work. The MIPs were synthesized by the “bulk” method using the quinoline molecule (IQ) as a template in different solvents, such as toluene (MIPT) and chloroform (MIPC). The adsorbents were characterized by thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and N₂ adsorption/desorption measurements. The influences of time, adsorbate concentration, and temperature on the adsorption of quinoline by MIPT and MIPC were evaluated. Maximum adsorption capacities (q_e) of 35.23 and 24.10 mg g⁻¹ were obtained for MIPT and MIPC, respectively. Thermodynamic studies indicate that occur physisorption and a spontaneous process (Δ_adsG° < 0) entropically directed. Finally, the highest selectivity and reusability of MIPC for quinoline adsorption was ascribed to the better interaction between the chloroform and monomer, which favors the formation of porous adsorbents with higher numbers of adsorption sites.

Molecularly imprinted polymers synthesized by a one-pot synthesis absorb quinoline efficiently and selectively.