Metal organic framework ZIF-90 modified with lactobionic acid for use in improved open tubular capillary electrochromatographic enantioseparation of five basic drugs

Zeolitic imidazolate frameworks (ZIFs): Advanced nanostructured materials to enhance the functional performance of food packaging materials

Zeolite imidazole framework (ZIF) materials are a class of metallic organic framework (MOF) materials that have several potential applications in the food and other industries. They consist of metal ions or clusters of metal ions coordinated with imidazole-based organic linkers, creating a three-dimensional solid structure with well-defined pores and channels. ZIFs possess several important features, including high porosity, tunable pore sizes, high surface areas, adjustable surface chemistries, and good stabilities. These characteristics make them highly versatile materials that can be used in a variety of applications, including smart and active food packaging. Based on their controllable compositions, dimensions, and pore sizes, the properties of ZIFs can be tailored for a diverse range of applications, including energy storage, sensing, separation, encapsulation, and catalysis. In this article, we focus on recent progress and potential applications of ZIFs in food packaging materials. Previous studies have shown that ZIFs can significantly improve the optical, mechanical, barrier, thermal, sustainability, and preservative properties of packaging materials. Moreover, ZIFs can be used as carriers to encapsulate, protect, and control the release of bioactive agents in packaging materials. ZIFs are capable of selectively adsorbing and releasing molecules based on their size, shape, and surface properties. These unique characteristics make them particularly suitable for smart or active food packaging applications. By selectively removing gases (such as oxygen, carbon dioxide, water, or ethylene) ZIFs can improve the shelf life and quality of packaged foods. In addition, they can be employed to control the growth of spoilage microorganisms and minimize oxidation reactions, thereby enhancing the freshness and extending the shelf life of foods. They may also be used to create sensors capable of detecting and indicating food spoilage. For instance, ZIFs that change color or release specific compounds when spoilage products are present can provide visual or chemical indications of food deterioration. This feature is especially valuable in ensuring the safety and quality of packaged food, as it enables consumers and retailers to easily identify spoiled products. ZIFs can be functionalized using various additives, including antioxidants, antimicrobials, pigments, and flavors, which can improve the preservative and sensory properties of packaged foods. Moreover, ZIF-based packaging materials offer sustainability benefits. Unlike traditional plastic packaging, ZIFs are biodegradable and can easily be disposed of without causing harm to the environment, thereby reducing the adverse effects of plastic waste materials. The application of ZIFs in smart/active food packaging offers exciting possibilities for enhancing the shelf life, quality, and safety of foods. With further research and development, ZIF-based packaging could become a sustainable alternative to plastic-based packaging in the food industry. An important aim of this review article is to stimulate further research on the development and application of ZIFs within food packaging materials.

Evaluation of deep eutectic solvents chiral selectors based on lactobionic acid in capillary electrophoresis

Recently, deep eutectic solvents (DESs) have attracted considerable interest in analytical chemistry. This work described the enantioseparations of twenty amino alcohol drugs with several DESs based on lactobionic acid (LA) as the sole chiral selector in capillary electrophoresis (CE) firstly. Compared to the single LA system and the ionic liquid/LA synergistic system, the DES system exhibited considerably improved separations. The influences of some key parameters on separations were investigated in detail. This work also experimentally demonstrated that the carboxyl group was indispensable in the process of chiral recognition. The mechanisms of the improvements of DESs on enantioseparations were studied via ultraviolet spectroscopy. Furthermore, the proposed method was used to determine the enantiomeric purity of propranolol hydrochloride successfully. This is the first time that chiral DESs were utilized as the sole chiral selectors in CE, and this strategy has opened up a new prospect for the use of DESs in enantioseparation.

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.

Evaluation of kasugamycin as a chiral selector in capillary electrophoresis

The discovery of novel chiral selectors always fascinates us. This work describes the chiral separation performances of a new chiral selector (kasugamycin, KAS) in capillary electrophoresis (CE) for six pairs of stereoisomers, including ephedrine and pseudoephedrine, quinine and quinidine, cinchonine and cinchonidine, and amlodipine, promethazine and ofloxacin enantiomers. Kasugamycin, an aminoglycoside antibiotic in agriculture, shows significant biological activity against rice blast with low toxicity. As it turns out, this new chiral selector possesses good CE compatibility and stereoselectivity towards model analytes. In this work, we systematically investigated several separation parameters including kasugamycin concentration, buffer pH, separation voltage and the composition of the buffer solution. A detailed discussion about the chiral recognition mechanism was made based on Statistical Product and Service Solution (SPSS) analysis, NMR experiments (1D and 2D) and molecular modeling. This is the first time that kasugamycin is utilized as a chiral selector in CE, and the development of new chiral selectors from agricultural or veterinary antibiotics deserves more attention.

Recent applications and chiral separation developments based on stationary phases in open tubular capillary electrochromatography (2019–2022)

Capillary electrochromatography (CEC) plays a significant role in chiral separation via the double separation principle, partition coefficient difference between the two phases, and electroosmotic flow-driven separation. Given the distinct properties of the inner wall stationary phase (SP), the separation ability of each SP differs from one another. Particularly, it provides large room for promising applications of open tubular capillary electrochromatography (OT-CEC). We divided the OT-CEC SPs developed over the past four years into six types: ionic liquids, nanoparticle materials, microporous materials, biomaterials, non-nanopolymers, and others, to mainly introduce their characteristics in chiral drug separation. There also added a few classic SPs that occurred within ten years as supplements to enrich the features of each SP. Additionally, we discuss their applications in metabolomics, food, cosmetics, environment, and biology as analytes in addition to chiral drugs. OT-CEC plays an increasingly significant role in chiral separation and may promote the development of capillary electrophoresis (CE) combined with other instruments in recent years, such as CE with mass spectrometry (CE/MS) and CE with ultraviolet light detector (CE/UV).

The progress on porous organic materials for chiral separation

Chiral compounds have similar structures and properties, but their pharmacological action is very different or even opposite. Therefore, the separation of chiral compounds has great significance in pharmaceutical and agriculture. Porous organic materials are novel crystalline porous materials, which possess high surface area, controllable pore size, and favorable functionalization. Therefore, porous organic materials are considered to be an ideal material for chiral separation. In this review, we summarized the progress of chiral porous organic materials for chiral separation in recent years. Furthermore, the applications of chiral porous organic materials as chiral separation medias (chromatography stationary phases and membrane materials) in enantioseparation were highlighted. Finally, the remaining challenges and future directions for porous organic materials in chiral separation were also briefly outlined further to promote the development of porous organic materials in chiral separation.

β-Cyclodextrin covalent organic framework supported by polydopamine as stationary phases for electrochromatographic enantioseparation

In this work, a new open-tubular capillary electrochromatography (OT-CEC) column was prepared using β-cyclodextrin covalent organic framework (β-CD COF) as a stationary phase. Polydopamine was used to assist fabrication of β-CD COF on an inner wall of a fused-silica capillary. The coating layer on the capillary was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Electroosmotic flow (EOF) was also studied to evaluate the variation of the inner wall of immobilized columns. Furthermore, the chiral separation effectiveness of the fabricated capillary column was evaluated by CEC using enantiomers of several related proton pump inhibitors as model analytes, including omeprazole, lansoprazole, pantoprazole and tenatoprazole. The effects of bonding time and concentration of β-CD COF, the type, concentration and pH of buffer, applied voltage were investigated to obtain satisfactory enantioselectivity. In the optimum conditions, the enantiomers of four analytes were resolved within 15 min with resolutions of 1.63-2.62. The relative standard deviation values for migration times and resolutions of the analytes representing intraday and interday were less than 6.75% and 4.24%, respectively. The results reveal that β-CD COF has great potential as chiral-stationary phases for enantioseparation in CEC.

MOFs and PDA-supported immobilization of BSA in open tubular affinity capillary electrochromatography: Prediction and study on drug-protein interactions

Owing to the satisfactory properties such as high specific surface area, finely tunable chemical composition, large yet adjustable pore sizes, and diverse architecture, metal-organic frameworks (MOFs) have the potential to be used as a stable, efficient, reusable and protective biomacromolecule immobilization carrier in capillary electrophoresis. Herein, a novel immobilized receptor open-tubular affinity capillary electrochromatography (OT-ACEC) strategy was developed for the first time to rapidly investigate the interactions between a set of drugs and bovine serum albumin (BSA). To further increase the amount of immobilized BSA and maintain the bioactivity of BSA, BSA was immobilized on the inner capillary surface by using polydopamine (PDA) as the adhesion layer and surface functionalization agent, a MOF namely dresden university of technology-5 (DUT-5) as supporting platform and biomacromolecule immobilization carrier, respectively. The amount of immobilized BSA on the capillary surface of the BSA@capillary and the PDA/MOFs/BSA@capillary column are separately calculated as 0.00756 nmol and 0.01812 nmol. Besides, the PDA/MOFs/BSA@capillary column was applied to investigate the interactions between BSA and flavonoids, fluoroquinolones. Under the optimal interaction conditions, three flavonoids and three fluoroquinolones are able to achieve baseline separation in the PDA/MOFs/BSA@capillary column (with resolution values of three flavonoids, 5.78 and 4.13; three fluoroquinolones, 1.72 and 1.68). The PDA/MOFs/BSA@capillary column shows good stability and reproducibility over 100 runs (relative standard deviation (RSD)＜5%). In addition, the normalized capacity factor (K_RCE) in this method replaced the binding constant and was used as an evaluation index to fast predict the activities of 20 drugs, some of which have not yet been reported for their interactions with BSA. Spectroscopy and molecular docking further illuminated the binding mechanism.

Capillary coated with three-dimensional covalent organic frameworks for separation of fluoroquinolones by open-tubular capillary electrochromatography

The Schiff-base reaction of 1,3,5-triformylphloroglucinol (Tp) and tetra(4-aminophenyl)methane (TAM) was performed for the synthesis of a three-dimensional covalent organic framework named 3D TpTAM, which was obtained by an ultrasound-assisted method for the first time. The morphology and structure of the synthesized TpTAM were characterized through various methods. Then, TpTAM-coated capillary columns were subsequently prepared by a covalent bonding method within a short time and applied for the separation of fluoroquinolones by capillary electrochromatography (CEC) with good resolution and reproducibility. The intraday relative standard deviations (RSDs) of the retention time and peak areas were 0.88%-0.95% and 2.27%-3.81%, respectively. The interday RSDs of retention time and peak areas were 0.71%-0.89% and 0.88%-3.60%, respectively. The column-to-column RSDs of retention time and peak areas were less than 1.90% and 13.56%, respectively. The interbatch RSDs of retention time and peak areas were less than 3.48% and 3.89%, respectively. The TpTAM-coated capillary columns could be used for no less than 100 runs with no observable changes in the separation efficiency. The separation mechanism was also studied, which indicated that π-π stacking effects, hydrophobic interactions and hydrogen bonding were the main factors. The results revealed that 3D TpTAM should have superior potential as the stationary phase in CEC for chromatographic separation.