Electrochromatographic separation of hydrophobic amino acid enantiomers by molecularly imprinted capillary columns

Monolithic capillary electrochromatographic enantioseparation system for dichlorprop based on a novel nanomaterial synthesized by chiral metal organic frameworks and racemic-templated chiral molecular imprinted polymers

Dichlorprop (DCPP), a chlorophenoxy herbicide with two enantiomers, shows distinct biological and toxicological properties: R-DCPP is highly effective as a herbicide, while S-DCPP lacks herbicidal activity and is toxic to non-target organisms. Efficient enantioseparation methods for DCPP are crucial for precise herbicide use, reduced agrochemical consumption, and minimized environmental impact. To achieve this purpose, a novel capillary monolithic column (L-His-ZIF-8@CMIP(rac-DCPP/PG-EDMA)@capillary) was fabricated using the nanomaterials synthesized by chiral molecularly imprinted polymers (CMIPs) and chiral metal-organic frameworks (CMOFs, L-His-ZIF-8) as stationary phases. Based on this innovative column, a capillary electrochromatography (CEC) system was established, enabling highly efficient enantioseparation of DCPP, precise chiral purity determination, and accurate quantitative analysis of individual enantiomers in complex real-world samples. During the synthesis of CMIPs, a novel functional monomer, allyl-β-d-Pyrone galactoside (PG), demonstrated unique "pre-chiral recognition" capability towards the racemic template (rac-DCPP) in the CMIP premix. This innovative approach enabled the successful synthesis of chirally selective CMIPs using rac-DCPP as template, rather than conventional single-enantiomer templates, in combination with ethylene dimethacrylate (EDMA) as the cross-linker. This synthesis strategy offers significant advantages, including substantial reduction in production costs and simplified synthesis procedures. To the best of our knowledge, this represents the first reported application of such methodology in CEC worldwide, as confirmed by comprehensive literature review. L-His-ZIF-8@CMIP(rac-DCPP/PG-EDMA)@capillary demonstrates remarkable enantioseparation capabilities through synergistic interactions between its components. Furthermore, the enantioseparation mechanism was systematically investigated through molecular docking and static adsorption experiments, providing fundamental insights into the chiral recognition process. This study establishes a groundbreaking approach for the development of racemic template-based CMIPs and the synthesis of advanced chiral stationary phases, offering significant potential for practical applications in chiral separation science.

Enantioseparation system based on a novel nanomaterial synthesized from chiral molecularly imprinted polymers and achiral metal-organic frameworks by capillary electrochromatography

A novel nanomaterial synthesized by chiral molecularly imprinted polymers (CMIPs) and achiral metal-organic frameworks (MOFs) was designed as stationary phase to prepare L-TRP@MIP(APTES-TEOS)@UiO-66-NH2@capillary for tryptophan enantioseparation in open tubular capillary electrochromatography. Compared with the capillary column coated only with CMIPs or achiral MOFs, this column remarkably improved the enantioseparation ability of tryptophan (resolution, 0.92/0 → 3.68). The chromatographic conditions (buffer pH, applied voltage, organic additive content) were optimized. Additionally, through static adsorption experiments, a conclusion was reached that the materials of stationary phase had stronger adsorption capacity for L-TRP than that for D-TRP, which revealed chiral separation mechanism of CEC system. This study opens up creative ideas for coating the novel nanomaterial in CEC system, which has good application prospects in the field of chiral separation.

Three-dimensional fluorinated covalent organic frameworks coated capillary for the separation of fluoroquinolones by capillary electrochromatography

In this work, a three-dimensional fluorinated covalent organic frameworks (3D FCOFs) JUC-515 was synthesized from tetra(4-aminophenyl)methane (TAM) and 2,3,5,6-tetrafluoroterephthalol (TFA) by an ionic liquid method. JUC-515 was introduced into the capillary column and bonded to the inner wall of the capillary column by chemical bonding. Through a variety of characterization results, JUC-515 was successfully synthesized and introduced into the capillary column. The effects of buffer solution concentration, organic additive content and pH of the buffer solution on the separation of fluoroquinolones (FQs) were investigated in detail. The JUC-515-coated capillary column showed good resolution (>1.5) and reproducibility. The relative standard deviations (RSDs) of the retention time for intraday, interday, column-to-column and interbatch precision were less than 0.88%, 2.45%, 2.74% and 3.32%, respectively. The RSDs of the peak area for intraday, interday, column-to-column and interbatch precision were less than 3.79%, 4.31%, 3.33% and 5.62%, respectively. The JUC-515-coated capillary column could be used no less than 150 times. The results showed that the JUC-515-coated capillary column had good separation performance. In addition, by separating fluorinated β-phenylalanine analogs, β-phenylalanine and trifluoromethyl β-phenylalanine analogs, the separation mechanism based on fluorine interactions was discussed. In conclusion, JUC-515 had good potential as a stationary phase for capillary electrochromatography.

Preparation of Immobilised 17β-Estradiol-Imprinted Nanoparticles onto Bacterial Cellulose Nanofibres to Use for the Removal of 17β-Estradiol from Wastewater

Estradiol, a phenolic steroid oestrogen, is one of the endocrine-disrupting chemicals (EDCs) found in natural and tap waters. The detection and removal of EDCs is attracting attention daily as they negatively affect animals' and humans' endocrine functions and physiological conditions. Therefore, developing a fast and practical method for the selective removal of EDCs from waters is essential. In this study, we prepared 17β-estradiol (E2)-imprinted HEMA-based nanoparticles onto bacterial cellulose nanofibres (E2-NP/BC-NFs) to use for the removal of E2 from wastewater. FT-IR and NMR confirmed the structure of the functional monomer. The composite system was characterised by BET, SEM, µCT, contact angle, and swelling tests. Additionally, the non-imprinted bacterial cellulose nanofibres (NIP/BC-NFs) were prepared to compare the results of E2-NP/BC-NFs. Adsorption of E2 from aqueous solutions was performed in batch mode and investigated via several parameters for optimisation conditions. The effect of pH studies was examined in the 4.0-8.0 range using acetate and phosphate buffers and a concentration of E2 of 0.5 mg/mL. The maximum E2 adsorption amount was 254 µg/g phosphate buffer at 45 °C. The experimental data show that the Langmuir is a relevant isotherm model for E2 adsorption. Additionally, the relevant kinetic model was the pseudo-second-order kinetic model. It was observed that the adsorption process reached equilibrium in less than 20 min. The E2 adsorption decreased with the increase in salt at varying salt concentrations. The selectivity studies were performed using cholesterol and stigmasterol as competing steroids. The results show that E2 is 46.0 times more selective than cholesterol and 21.0 times more selective than stigmasterol. According to the results, the relative selectivity coefficients for E2/cholesterol and E2/stigmasterol were 8.38 and 86.6 times greater for E2-NP/BC-NFs than for E2-NP/BC-NFs, respectively. The synthesised composite systems were repeated ten times to assess the reusability of E2-NP/BC-NFs.

Molecularly imprinted polymers in toxicology: a literature survey for the last 5 years

The science of toxicology dates back almost to the beginning of human history. Toxic chemicals, which are encountered in different forms, are always among the chemicals that should be investigated in criminal field, environmental application, pharmaceutic, and even industry, where many researches have been carried out studies for years. Almost all of not only drugs but also industrial dyes have toxic side and direct effects. Environmental micropollutants accumulate in the tissues of all living things, especially plants, and show short- or long-term toxic symptoms. Chemicals in forensic science can be known by detecting the effect they cause to the body with the similar mechanism. It is clear that the best tracking tool among analysis methods is molecularly printed polymer-based analytical setups. Different polymeric combinations of molecularly imprinted polymers allow further study on detection or extraction using chromatographic and spectroscopic instruments. In particular, methods used in forensic medicine can detect trace amounts of poison or biological residues on the scene. Molecularly imprinted polymers are still in their infancy and have many variables that need to be developed. In this review, we summarized how molecular imprinted polymers and toxicology intersect and what has been done about molecular imprinted polymers in toxicology by looking at the studies conducted in the last 5 years.