Graphene oxide coated capillary for chiral separation by CE: CE and CEC

Surface modified nanoparticles and their applications for enantioselective detection, analysis, and separation of various chiral compounds

The development of efficient enantioselective detection, analysis, and separation relies significantly on molecular interaction. In the scale of molecular interaction, nanomaterials have a significant influence on the performance of enantioselective recognitions. The use of nanomaterials for enantioselective recognition involved synthesizing new materials and immobilization techniques to produce various surface-modified nanoparticles that are either encapsulated or attached to surfaces, as well as layers and coatings. The combination of surface-modified nanomaterials and chiral selectors can improve enantioselective recognition. This review aims to offer engagement insights into the production and application of surface-modified nanomaterials to achieve sensitive and selective detection, better chiral analysis, and separation of numerous chiral compounds.

A graphene oxide-molybdenum disulfide composite used as stationary phase for determination of sulfonamides in open-tubular capillary electrochromatography

A graphene oxide-molybdenum disulfide (GO-MoS₂) composite was synthesized and utilized as the highly efficient stationary phase of open-tubular capillary electrochromatography (OT-CEC). The characterization results indicated that GO-MoS₂ composite was successfully synthesized. The GO-MoS₂-coated capillary column was prepared by covalent immobilization method for the determination of seven sulfonamides. The baseline separation of seven sulfonamides was achieved by GO-MoS₂-coated capillary column. The linear range was 0.05-100 μg/mL for sulfisomidine, sulfathiazole, sulfamerazine, phthalylsulfathiazole and sulfacetamide, 0.1-100 μg/mL for sulfamonomethoxine and sulfachloropyridazine with a satisfactory correlation coefficients (R²) > 0.9994. This developed OT-CEC method was successfully applied to determinate of seven sulfonamides in environmental water and milk samples with good recoveries of 85.77% - 109.10% and 80.03% - 109.97%, respectively. These results indicated that GO-MoS₂-coated capillary column possessed good stability and repeatability.

Rapid preparation and evaluation of chiral open-tubular columns supported with bovine serum album and zeolite imidazolate framework-8 for mini-capillary electrochromatography

In this work, a class of novel and eco-friendly open-tubular (OT) chiral column was presented for the first time by one step preparation with zeolite imidazolate framework-8 (ZIF-8) and bovine serum album (BSA) based on electrostatic adsorption and adsorption affinity. This stationary phase materials combined the features of large surface areas and adsorption affinity of ZIF-8, and also the multiple chiral binding sites of BSA, which contributes to the π-interaction and hydrophobic interaction with the analytes. The separation performance of BSA@ZIF-8-OT chiral columns was evaluated with a miniaturized capillary electrochromatography and amperometric detection (mini-CEC-AD) system; in particular, nine groups of model molecules, including homologues, structural isomers, and chiral compounds, were baseline separated under the certain optimum conditions. The RSDs of run-to-run, day-to-day, column-to-column, and batch-to-batch reproducibility were less than 13.8 %. Furthermore, the prepared OT columns were successfully applied to fast analysis of ephedrine isomers in Chinese herb ephedra, and the LODs achieved 1.5-2.0 ng mL^-1 (S/N=3) by an electrophoretic stacking technique of moving chemical reaction boundary. This mini-CEC-AD system with BSA@ZIF-8-OT chiral columns provides a promising potential in pharmaceutical analysis due to its fast, sensitive, enantioselective, and low-cost characteristics.

Zeolite silica nanoparticles-supported open-tubular columns for isomer and chiral separation using capillary electrochromatography coupled with amperometric detection

Zeolite SiO₂NPs OT columns with/without BSA were used for the separation of structural isomers, epimers and enantiomers by CEC-AD.

Ambient temperature fabrication of a covalent organic framework from 1,3,5-triformylphloroglucinol and 1,4-phenylenediamine as a coating for use in open-tubular capillary electrochromatography of drugs and amino acids

A covalent organic framework (COF) named TpPa-1 was designed and synthesized at ambient temperature by an ultrasound-assisted method from 1,3,5-triformylphloroglucinol (Tp) and 1,4-phenylenediamine (Pa-1). It was utilized as a stationary phase in open-tubular capillary electrochromatography (OT-CEC). The column was coated with TpPa-1 using a covalent bonding strategy. The coated capillary was characterized by morphology, crystallography, and mesoporous analysis to confirm the successful fabrication. The OT-CEC method was utilized for the analysis of tetracyclines, sulfonamides, cephalosporins and amino acids with high-resolution (Rs > 1.81) and good precision (RSD < 4.9%). It takes about 12 h from COF preparation to OT-CEC separation. Graphical abstract A covalent organic framework (COF) named TpPa-1 was synthesized at ambient temperature by an ultrasound-assisted method from 1,3,5-triformylphloroglucinol (Tp) and 1,4-phenylenediamine (Pa-1). COF-TpPa-1 modified capillary column was utilized for the analysis of tetracyclines, sulfonamides, cephalosporins and amino acids with high-resolution and good precision.

Enantiomeric Recognition and Separation by Chiral Nanoparticles

Chiral molecules are stereoselective with regard to specific biological functions. Enantiomers differ considerably in their physiological reactions with the human body. Safeguarding the quality and safety of drugs requires an efficient analytical platform by which to selectively probe chiral compounds to ensure the extraction of single enantiomers. Asymmetric synthesis is a mature approach to the production of single enantiomers; however, it is poorly suited to mass production and allows for only specific enantioselective reactions. Furthermore, it is too expensive and time-consuming for the evaluation of therapeutic drugs in the early stages of development. These limitations have prompted the development of surface-modified nanoparticles using amino acids, chiral organic ligands, or functional groups as chiral selectors applicable to a racemic mixture of chiral molecules. The fact that these combinations can be optimized in terms of sensitivity, specificity, and enantioselectivity makes them ideal for enantiomeric recognition and separation. In chiral resolution, molecules bond selectively to particle surfaces according to homochiral interactions, whereupon an enantiopure compound is extracted from the solution through a simple filtration process. In this review article, we discuss the fabrication of chiral nanoparticles and look at the ways their distinctive surface properties have been adopted in enantiomeric recognition and separation.

Mechanistic evaluation of anti-arthritic activity of β-methylphenylalanine in experimental rats

Arthritis is a common chronic joint disorder, with general symptoms including stiffness and joint pain. β-methylphenylalanine is a well-known non-proteogenic unnatural amino acid. This study analyzes the anti-arthritic activity of β-methylphenylalanine in experimental rats. The experimental groups were as follows: group I, sham; group II, control; group III, 100 mg/kg of β-methylphenylalanine; and group IV, 200 mg/kg of β-methylphenylalanine. Lipid peroxidation, glutathione peroxidase (Gpx), reduced glutathione (GSH), superoxide dismutase (SOD), catalase, prostaglandin E₂ (PGE₂), matrix metalloproteinase-3 (MMP-3), ceruloplasmin, zinc, copper, mRNA, and protein expression of inducible nitric oxide synthase (iNOS) and nuclear factor-kappa B (NF-κB) were determined. Supplementation with β-methylphenylalanine significantly reduced lipid peroxidation, copper, PGE₂ and MMP-3 levels, whereas GSH, Gpx, catalase, SOD and zinc levels were increased. Supplementation with β-methylphenylalanine significantly reduced NF-κB mRNA expression by 26% and 47.8% in groups III and IV, respectively (P < 0.045), while iNOS mRNA expression was reduced by 14.3 and 47.6% in groups III and IV, respectively. NF-κB and iNOS protein expression increased by 160% and 120% respectively, in the control rats compared to the sham rats. However, supplementation with β-methylphenylalanine significantly reduced NF-κB protein expression by 27% and 50% in groups III and IV, respectively, while iNOS protein expression was reduced by 22.7% and 45.4% in groups III and IV, respectively. Taken together, our data show that supplementation of β-methylphenylalanine was effective against arthritis in a rat model.

Polyethylene Glycols for the Dispersion Development of Graphene in an Aqueous Surfactant Solution Studied by Affinity Capillary Electrophoresis

Water-soluble nonionic polymers of polyethylene glycol (PEG), poly(vinyl alcohol) (PVA), and polyvinylpyrrolidone (PVP) were examined to develop the dispersion of graphene in an aqueous surfactant solution. Sodium dodecylbenzenesulfonate was used as an anionic surfactant to disperse graphene in an aqueous solution and to give negative charge on it. The dispersion of graphene was monitored through the electropherograms in affinity capillary electrophoresis; a broad peak for the dispersed graphene and shot signals for the aggregated one. When PEG was added in the separation buffer as an affinity reagent, the number of the shot signals in the electropherogram was reduced; PEG can develop the dispersion of graphene in an aqueous surfactant solution. The dispersion was also developed with PVP or PVA. The effective electrophoretic mobility of the dispersed graphene was reduced by using the polymer as an affinity reagent. The result suggested that the anionic surfactant on the graphene surface was competitively substituted with the nonionic polymer. The degree of the decrease in the effective electrophoretic mobility was larger with PEG with a high-molecular mass. The broad peak of the dispersed graphene got narrower by the addition of PEG, and the number of theoretical plates was improved.

Preparation and evaluation of a polydopamine-modified capillary silica monolith for capillary electrochromatography

A novel capillary silica monolith (CSM) with surface modification was prepared for capillary electrochromatography (CEC) by using polydopamine (PDA) as a functional coating.

Open-tubular capillary electrochromatographic determination of ten sulfonamides in tap water and milk by a metal-organic framework-coated capillary column

In this study, a metal-organic framework (MOF), [Mn(cam)(bpy)], was synthesized and characterized by thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectrometry. An open-tubular capillary column was fabricated from [Mn(cam)(bpy)] via the amide coupling method. Ten types of sulfonamides were separated through the fabricated capillary column, which showed a good limits of detection (<0.07 μg/mL) and linear ranges (1-100 or 5-100 μg/mL) with a high correlation coefficients (R² > 0.9987). The intra-day, inter-day and column-to-column relative standard deviations (RSDs) in the migration times ranged from 0.44 to 4.87%, and the peak area RSDs ranged from 0.80 to 7.28%. The developed capillary electrochromatography method can be successfully utilized for the determination of sulfonamides in tap water and milk samples.

Covalent bonding of Schiff base network-1 as a stationary phase for capillary electrochromatography

Covalent organic frameworks (COFs), featuring low densities, high surface areas, and good thermal and chemical stabilities, are gradually attracting interest in the field of analytical chemistry. A type of microporous polymer network material named Schiff base network-1 (SNW-1) was introduced into a capillary column through covalent bonding. The obtained SNW-1-coated capillary column was characterized by thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Then, the SNW-1-coated capillary column was successfully utilized for the open-tubular capillary electrochromatography (OT-CEC) separation of sulfonamides, cephalosporins, amino acids and parabens. The fabricated capillary column showed good separation efficiency (R_s > 1.4), stability and reproducibility (relative standard deviation (RSD) < 5.88%). To the best of our knowledge, this is the first report of a covalent bonding strategy to bond an SNW material to a capillary column for OT-CEC.

Recent advances in metal-organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF- or COF-based solid-phase extraction (SPE), solid-phase microextraction (SPME), gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.

Graphene nanoparticles as pseudostationary phase for the electrokinetic separation of nonsteroidal anti-inflammatory drugs

The exceptional properties of graphene (G) were exploited here to facilitate capillary electrokinetic separations. Two types of commercially available G consisting of nanoparticles containing-one to three and-four to six G sheets, respectively, were compared for this purpose. Both proved effective in separating the arylpropyl derivatives of nonsteroidal anti-inflammatory drugs. The highest resolution and shortest migration times were obtained with G containing high amount of single and double G nanosheets. G affords higher resolution than other types of nanoparticles; stable suspensions can be easily prepared and used as BGE without the need of adding an additional surfactant. This results in a high reproducibility in migration times and stability in background noise. The LOD and LOQ obtained by using G nanoparticles as pseudostationary phases spanned the range 0.29-1.18 mg/L and 0.95-3.95 mg/L, respectively, and the RSD was less than 4.7% in all instances.

Simultaneous determination of atropine, scopolamine, and anisodamine in Flos daturae by capillary electrophoresis using a capillary coated by graphene oxide

A novel CE method was developed for the separation and determination of three main tropane alkaloids in Flos daturae with a capillary coated by graphene oxide (GO). The GO-coated capillary was characterized by SEM, energy dispersive X-ray spectroscopy, and Raman spectroscopy, and the results indicated that the inner surface of the capillary was partially coated by GO. A phosphate solution (40 mM, pH7.0) containing 20% v/v methanol and 30% v/v acetonitrile was used as the running buffer for the analysis of the atropine, scopolamine, and anisodamine. The linear ranges of atropine, scopolamine, and anisodamine was 0.5-200 μg/mL with satisfactory correlation coefficients (R(2)) > 0.9987, and this novel method provided an efficient separation for three tropane alkaloids as well as a good reproducibility and stability. Finally, the method was successfully applied for the determination of these three tropane alkaloids in plant extracts.