Detection and adsorption of florfenicol in milk using bifunctional carbon dot-doped molecularly imprinted polymers.

Detection of florfenicol (FF) residues in animal-derived foods, as one of the most widely used antibiotics, is critically important to food safety. The fluorescent molecularly imprinted polymer (MIP) was synthesized by surface-initiated atom transfer radical polymerization technique with poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres, 4-vinylpyridine, ethylene glycol dimethacrylate, and FF as the matrix, functional monomer, crosslinker, and template molecule, respectively. Meanwhile, N-S co-doped carbon dot (CD) was synthesized with triammonium citrate and thiourea as precursors under microwave irradiation at 400 W for 2.5 min and then integrated into FF-MIP to obtain CD@FF-MIP. For comparison, non-imprinted polymer (NIP) without FF was also prepared. The adsorption capacity of CD@FF-MIP to FF reached 53.1 mg g-1, which was higher than that of FF-MIP (34.7 mg g-1), whereas the adsorption capacity of NIP was only 17.3 mg g-1. The adsorption equilibrium of three materials was reached within 50 min. Particularly, CD@FF-MIP exhibited an excellent fluorescence quenching response to FF in the concentration range of 3-50 µmol L-1. As a result, CD@FF-MIP was successfully utilized to extract FF in milk samples, which were analyzed by high-performance liquid chromatography. The standard recoveries were 95.8%-98.2%, and the relative standard deviation was 1.6%-4.2%. The method showed the advantages of simple operation, high sensitivity, excellent selectivity, and low cost, and also demonstrated a great application prospect in food detection.

Preparation and chromatographic evaluation of hydrophilic polymer brushes grafted-silica with post modification of silicon/carbon dots as a green liquid chromatography stationary phase.

Polar stationary phases were prepared by grafting hydrophilic acrylamide (Am) polymer brushes with post modification of carbon dots (CDs) and silicon dots (SiDs) onto SiO2 particles. The prepared stationary phases, SiO2-PAm-CDs, SiO2-PAm-CDs/SiDs, and SiO2-PAm-SiDs, were packed as chromatographic columns, respectively. Using nucleic bases, organic acids, and ß-agonists as target substances to investigate the influence of chromatographic conditions on retention and separation, the packed columns showed the partitioning and adsorption of mixed retention behavior in hydrophilic interaction liquid chromatography mode and successfully separated the polar compounds. Most importantly, under per aqueous liquid chromatography mode (using 100% water as mobile phase), those columns still had good separation ability toward nucleic bases, ß-agonist, and organic acids. Because AM is a temperature-sensitive monomer, the resulting van't Hoff curves exhibited a nonlinear relationship, having temperature-responsive chromatographic characteristic under pure water separation. Hence, building on temperature-sensitive characteristics and pure water of separation conditions, the separation selectivity toward hydrophilic compounds greatly improved. Compared with the commercial hydrophilic columns, the efficiency of our developed column had the superior ability in separation and detection of betaine in Goji berry with the enhanced resolution achieved in the proposed green separation method (just using pure water as mobile phase).

Selective adsorption and identification of penicillin G sodium in milk by molecularly imprinted polymer doped carbon dot.

A carbon dot (CD) was prepared by o-phenylenediamine and water, which showed bright yellow fluorescence under ultraviolet light irradiation (λ = 580 nm), and verified good fluorescence quenching effect on penicillin G sodium (Png-Na). Using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, and Png-Na as a template, a kind of composite microsphere combining CD and molecularly imprinted polymer (MIP) was synthesized by surface-initiated atomic transfer radical polymerization (SI-ATRP). For reasons of comparison, we also prepared MIP without CD and non-imprinted polymers (NIPs). Through static and dynamic adsorption experiments, the maximum adsorption capacity was 47.05 mg g-1 and the equilibrium time was 30 min. High-performance liquid chromatography (HPLC) was utilized to determine the content of Png-Na in the spiked milk samples. A sensitive, rapid, and simple method for determination of Png-Na in food samples was developed. The utilized approach enabled the quantification of Png-Na within the concentration range 20-1000 µg L-1 (with a limit of detection of 5 µg L-1). The recoveries achieved were in the range 93.3-98.2%, with a relative standard deviation of 1.2-4.2%. The results demonstrated that CD@MIP possessed the capability of specific adsorption and fluorescence detection of Png-Na, enabling simultaneous detection and enrichment of Png-Na in real samples.

Fabrication of molecularly imprinted resin via controlled polymerization applied in the enrichment of bisphenol A for plastic products.

The addition of bisphenol A has been frequently used in industrial manufacturing because it imparts plastic products with characteristics such as transparency, durability, and excellent impact resistance. However, its widespread use raises concerns about potential leakage into the surrounding environment, which poses a significant risk to human health. In this study, molecularly imprinted polymers with specific recognition of bisphenol A were synthesized through surface-initiated atom transfer radical polymerization using poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) as the substrate, bisphenol A as the template molecule, 4-vinylpyridine as the monomer, and ethylene glycol dimethacrylate as the cross-linker. The bisphenol A adsorption capacity was experimentally investigated, and the kinetic analysis of the molecularly imprinted polymers produced an adsorption equilibrium time of 25 min, which is consistent with the pseudo-second-order kinetic model. The results of the static adsorption experiments exhibited consistency with the Langmuir adsorption model, revealing a maximum adsorption capacity of 387.2 µmol/g. The analysis of molecularly imprinted polymers-enriched actual samples using high-performance liquid chromatography demonstrated excellent selectivity for bisphenol A, with a linear range showing 93.4%-99.7% recovery and 1.1%-6.4% relative standard deviation, demonstrating its high potential for practical bisphenol A detection and enrichment applications.

Controllable preparation of a hydrophilic/ion-exchange mixed-mode stationary phase by surface-initiated atom transfer radical polymerization using a mixture of two functional monomers.

Mixed-mode chromatographic stationary phases require functionalization with at least two functional groups to yield multiple interactions with analytes. Departing from reported methods, a mixture of two different monomers, glycidyl methacrylate and 2-dimethylaminoethylmethacrylate, was grafted onto the surface of silica by a one-step surface-initiated atom transfer radical polymerization to prepare a novel hydrophilic interaction/anion-exchange mixed-mode chromatographic stationary phase. The grafted amounts of functional groups were controlled via varying the ratio of monomers in the polymerization system. The influences of water content, salt concentration and pH in the mobile phase were investigated to illustrate the mixed interaction between the stationary phase and analytes. The retention of various solutes on three columns, especially acidic and basic solutes, showed an obvious dependence on the ratio of the two monomers in the polymerization system. The results indicated that the strategy proposed in this work was beneficial to develop various types of mixed-mode chromatographic stationary phases with adjustable selectivity to meet the needs of complex samples. Finally, the column was successfully employed in the isolation of melamine in liquid milk.

Novel bis(5-methyltetrazolium)amine ligand-bonded stationary phase with reduced leakage of metal ions in immobilized metal affinity chromatography of proteins.

Immobilized metal affinity chromatography (IMAC) has been widely used for the specific separation of biopolymers. However, leakage of metal ions from IMAC adsorbents is of concern in IMAC. In this study, we designed a novel tridenate bis(5-methyltetrazolium)amine (BMTA) to reduce the leakage of metal ions by improving the affinity to immobilized metal ions. The ligand was bonded onto silica via three-step reaction to prepare a high-performance IMAC stationary phase. The chromatographic behaviors of ribonuclease A, cytochrome c, and lysozyme on the Cu(II)-, Ni(II)-, and Zn(II)-chelated stationary phase were investigated with respect to pH effect and elution with an imidazole gradient. The retention times of these three proteins increased by increasing the pH of the mobile phase but decreased by increasing the concentration of the competitive displacer. The retaining strength of the three proteins on the chelated stationary phase were in the order Cu(II) > Ni(II) > Zn(II). The behavior of these three proteins was consistent with the properties of a typical IMAC. The BMTA ligand exhibited a much stronger affinity for Cu(II) and Ni(II) than iminodiacetic acid (IDA), which is often regarded as a standard tridentate IMAC ligand. Quantum mechanical calculations at the B3LYP/6-31G level were used to image the coordination mode of the protein-metal ions-BMTA complex. In addition, a fused histidine-tagged cecropin b-human epidermal growth factor (CB-EGF) from Escherichia coli crude extract was purified by the Ni(II)-chelated stationary phase, and the purity of the CB-EGF was determined to be at least 90 %. These results suggest that the BMTA ligand may have potential applications in the preparation of therapeutics. Graphical Abstract A novel ligand of tridenate bis(5-methyltetrazolium)amine (BMTA) was designed to reduce the leakage of metal ions from the column in immobolized metal affinity chromatography (IMAC).

Luminescent Ln-MOFs for Chemical Sensing Application on Biomolecules.

At present, the application of rare-earth organic frameworks (Ln-MOFs) in fluorescence sensing has entered rapid development and shown great potential in various analytical fields, such as environmental analysis, food analysis, drug analysis, and biological and clinical analysis by utilizing their internal porosity, tunable structural size, and energy transfer between rare-earth ions, ligands, and photosensitizer molecules. In addition, because the luminescence properties of rare-earth ions are highly dependent on the structural details of the coordination environment surrounding the rare-earth ions, and although their excitation lifetimes are long, they are usually not burst by oxygen and can provide an effective platform for chemical sensing. In order to further promote the development of fluorescence sensing technology based on Ln-MOFs, we summarize and review in detail the latest progress of the construction of Ln-MOF materials for fluorescence sensing applications and related sensor components, including design strategies, preparation methods, and modification considerations and initially propose the future development prospects and prospects.

Zwitterionic polymers grafting of metal organic framework encapsulated boronic acid carbon dots as antibiofouling fluorescent probe for baicalin monitoring.

The sensitivity and accuracy of fluorescence probes for biological samples are affected by not only interfering molecule compounds but also the nonspecific adsorption of proteins and other macromolecules. Herein, fluorescence probe based on zwitterionic sulfobetaine methacrylate polymer (PSBMA) as an antibiofouling layer and amino boric acid carbon dots encapsulated in the metal-organic framework UiO-66-NH2 (UiO-66-NH2/BN-CDs) as a target recognition site was designed for the detection of baicalin (BAI). Owing to the introduction of BN-CDs into UiO-66-NH2 with high specific surface area, the prepared UiO-66-NH2/BN-CDs@PSBMA probe exhibited a high adsorption capacity of 78.9 mg g-1, while presented fluorescence enhancing and superior fluorescence selectivity to BAI at excitation and emission wavelengths of 400 and 425 nm, respectively. Connecting PSBMA with good hydrophilicity to UiO-66-NH2, resulted in an anti-protein capacity of over 96.3 %, effectively inhibiting protein interference with the fluorescence signal. By virtue of its good antibiofouling and recognizing capacities, the fluorescence probe exhibited a satisfactory detection range of 10-80 nmol L-1, with a fairly low detection limit of 0.0064 µmol L-1. Using the method to detect BAI in Goji berry, Sophora and Yinhuang oral solution, demonstrating its potential for the accurate and quantitative detection of BAI in complex biological samples.

The distribution and enrichment characteristics of rare earth elements between coals and coal ashes from four coal-fired power plants.

Coal and coal ash (slag and fly ash) have emerged as important potential sources for rare earth elements (REY). The distribution and enrichment of REY during coal combustion from coal-fired power plants are of great significance for the recovery of REY. In this study, the concentration of REY in coal and coal ash from four coal-fired power plants in China was determined using microwave digestion-inductively coupled plasma mass spectrometry. The distribution and enrichment characteristics of REY in coal and coal ash were studied. The coal ash contains 310-683 µg g-1 of REY, and the proportion of critical REY was greater than 30%, which is higher than the extraction concentration (300 µg g-1) recommended by the United States Department of Energy, indicating significant REY recovery potential. The concentration of REY in coal was positively correlated with ash yield, which could be explained by the fact that REY are mainly distributed in minerals. Coal and coal ash show similar REY distribution patterns, indicating that REY were not fractionated during the coal combustion. In addition, the enrichment coefficient of REY in fly ash was greater than that in slag, which revealed that REY were mainly enriched in fly ash. Therefore, the REY in fly ash has more recycling potential.

Bifunctional fluorescent molecularly imprinted resin based on carbon dot for selective detection and enrichment of 2,4-dichlorophenoxyacetic acid in lettuce.

The work provided a method for synthesizing a simple fluorescent molecularly imprinted polymer by surface-initiated atom transfer radical polymerization (SI-ATRP) and its application in real sample. Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres were selected as a matrix, 4-vinylpyridine, ethylene glycol dimethacrylate, 2,4-dichlorophenoxyacetic acid (2,4-D) as functional monomer, cross-linker and template molecule, respectively, to fabricate MAR@MIP with core-shell structure. For comparison, carbon dot (CD) as a fluorescence source was synthesized with o-phenylenediamine and tryptophan as precursors via hydrothermal method and integrated into MIP to acquire MAR@CD-MIP. MAR@CD-NIP was also prepared without adding the template molecule. The adsorption capacity of MAR@CD-MIP reached 104 mg g-1 for 2,4-D, which was higher than that of MAR@MIP (60 mg g-1). However, the adsorption capacity of MAR@CD-NIP was only 13.2 mg g-1. The linear range of fluorescence detection for 2,4-D was 18-72 µmol/L, and the limit of detection (LOD) was 0.35 µmol/L. The fluorescent MAR@CD-MIP was successfully applied in enrichment of lettuce samples. The recoveries of the three spiked concentrations of 2,4-D in lettuce were tested by fluorescence spectrophotometry and ranged in 97.3-101.7 %. Meanwhile, the results were also verified by HPLC. As a result, bi-functional molecularly imprinted resin was successfully fabricated to detect and enrich 2,4-D in real samples, and exhibited good selectivity, sensitivity and great application prospect in food detection.

Detection and adsorption of 2-methyl-4-chlorophenoxyacetic acid in vegetables via dual-functional molecularly imprinted polymer doping with carbon dot.

2-Methyl-4-chlorophenoxyacetic acid (MCPA) is one of the most widely used herbicides, so adsorption and detection of MCPA in the environment is critical. Blue fluorescent carbon dot (CD) was synthesized from citric acid and urea, which could be quenched by MCPA. Herein, bifunctional molecularly imprinted polymer (CD@MIP) was prepared on monodisperse poly (glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres, with 4-vinylpyridine as the functional monomer, ethylene glycol dimethacrylate as the cross-linking agent, and doped with CD. The enrichment ability of CD@MIP for MCPA and fluorescence detection performance were determined. The maximum adsorption amount of MCPA was 93.9 mg g-1 as determined by isothermal adsorption experiments and was in accordance with the Langmuir adsorption model. The results of the kinetic experiments showed that the adsorption equilibrium reached within 30 min, which possessed a relatively fast adsorption rate and was in accordance with the pseudo-second-order adsorption model. Both MIP without CD and non-imprinted polymers were also fabricated and tested as references. Fluorescence experiments showed good linearity of CD@MIP in the range of 0-80 µmol. The cabbage samples were analyzed by high performance liquid chromatography with a linear range of 0.02-15 µg mL-1, recoveries of 90.5%-98% and low relative standard deviations (RSD, n = 3) of 1.5%-5.9%. CD@MIP with excellent performance provides a feasible practical application in the detection and enrichment of MCPA.

Internal multiple interactions-adsorption and external zwitterionic polymer-exclusion of restricted access materials as adsorbent for offline and online extraction of neonicotinoid pesticides in Goji samples.

A method based on novel restricted access materials (RAMs) for the determination of neonicotinoid pesticides in Goji samples using offline and online solid phase extraction (SPE) coupled with high-performance liquid chromatography (LC). RAMs were synthesized using poly(chloromethylstyrene-co-divinylbenzene) (PVBC/DVB) microspheres as substrate, styrene (St) and n-vinylpyrrolidone (NVP) were first copolymerized on the interior to construct adsorption sites, and sulfobetaine methacrylate (SBMA) was then polymerized on the exterior to form exclusion sites via two-step surface initiated-atom transfer polymerization. The prepared PVBC/DVB@poly(St-co-NVP)@poly(SBMA) RAMs could efficiently extract neonicotinoid pesticides and automatically exclude proteins. Under the optimized conditions, the developed methods of offline (magnetic SPE and SPE column) and online extraction coupled with LC both using PVBC/DVB@poly(St-co-NVP)@poly(SBMA) RAMs as the extractant, exhibit a wide linearity, low limits of detection and limit of quantification and good inter-day and intra-day precision with satisfactory recoveries. Among these methods, online extraction coupled with LC based on novel RAMs exhibits clear advantages for the determination of neonicotinoid pesticides in Goji samples has clear advantages, such as simple operation by direct injection, short extraction times, and high accuracy with less human error.

Simple fabrication of carbon quantum dots and activated carbon from waste wolfberry stems for detection and adsorption of copper ion.

Removal of heavy metal pollution is an endless topic, because heavy metals can cause irreversible damage to the human body and environment. It is urgent to develop novel materials for detection and adsorption of heavy metal ions. In this paper, waste wolfberry straw was utilized as a carbon source, and two simple methods were developed to successfully prepare activated carbon (AC) and carbon quantum dots (CQDs). The fabrication conditions were optimized by adjusting the mass ratio of precursor to activator, type of activator and activation times. When sodium hydroxide (NaOH) was selected as an activator (6 : 1, mass ratio of NaOH to AC-precursor), and the activation was performed at 600 °C for 1 h, the highest specific surface area of the obtained AC-NaOH-3 reached 3016 m2 g-1. The adsorption capacity for copper ions (Cu2+) reached 68.06 mg g-1. The preparation conditions for CQDs were also optimized by adjusting the concentration of wolfberry stem, reaction time and temperature. When the wolfberry stem concentration was 7.5 g L-1, and the activation was performed at 200 °C for 24 h, the obtained CQDs exhibited strong fluorescence emission in the blank and 12 kinds of metal ion solutions, respectively, however, the fluorescence intensity was remarkably decreased after adding Cu2+. In the range of 10-80 nM, the linear correlation coefficient between the concentration of Cu2+ and fluorescence intensity of CQDs was 0.992, and the limit of detection was 2.83 nmol L-1. Thus, these two kinds of materials were prepared from wolfberry stem, which opened up a new way for the application in adsorption and detection of copper ions.

Adsorption of heavy metal onto biomass-derived activated carbon: review.

Due to the rapid development of the social economy and the massive increase in population, human beings continue to undertake processing, and commercial manufacturing activities of heavy metals, which has caused serious damage to the environment and human health. Heavy metals lead to serious environmental problems such as soil contamination and water pollution. Human health and the living environment are closely affected by the handling of heavy metals. Researchers must find several simple, economical and practical methods to adsorb heavy metals. Adsorption technology has been recognized as an efficient and economic strategy, exhibiting the advantages of recovering and reusing adsorbents. Biomass-derived activated carbon adsorbents offer large adjustable specific surface area, hierarchically porous structure, strong adsorption capacity, and excellent high economic applicability. This paper focuses on reviewing the preparation methods of biomass-derived activated carbon in the past five years. The application of representative biomass-derived activated carbon in the adsorption of heavy metals preferentially was described to optimize the critical parameters of the activation type of samples and process conditions. The key factors of the adsorbent, the physicochemical properties of the heavy metals, and the adsorption conditions affecting the adsorption of heavy metals are highlighted. In addition, the challenges faced by biomass-derived activated carbon are also discussed.

Preparation of Ganoderma Lucidum Bran-Based Biological Activated Carbon for Dual-Functional Adsorption and Detection of Copper Ions.

In this paper, Ganoderma lucidum bran was explored as the precursor to fabricate biomass activated carbon. When potassium hydroxide was selected as an activator (1:6, mass ratio of AC-12 to potassium hydroxide), and the activation condition was 700 °C at 5 h, the highest specific surface area reached 3147 m2 g-1. Carbon dots were prepared with citric acid monohydrate and thiourea as precursors and then loaded onto the surface of activated carbon by a simple and green method. Activated carbon for dual-functional had a high adsorption capacity. Additionally, based on its unique optical properties, the fluorescence response for detecting copper ion was established. The fluorescence intensity of the materials decreased linearly with the increase of copper ion concentration, in the range of 10-50 nmol L-1. The research opened up a new way for applying biomass activated carbon in the field of adsorption and detection. Highlights: (1) Carbon dots were loaded on the surface of activated carbon; (2) the simultaneous adsorption and detection were realized; (3) it provides a way for the preparation of dual-functional materials.

Ganoderma lucidum bran-derived blue-emissive and green-emissive carbon dots for detection of copper ions.

Ganoderma lucidum bran (GB) has a broad application prospect in the preparation of activated carbon, livestock feed, and biogas, but the preparation of carbon dots (CDs) from GB has never been reported. In this work, GB was applied as a carbon source and nitrogen source to prepare both blue fluorescent CDs (BCDs) and green fluorescent CDs (GCDs). The former were prepared at 160 °C for 4 h by a hydrothermal approach, while the latter were acquired at 25 °C for 24 h by chemical oxidation. Two kinds of as-synthesized CDs exhibited unique excitation-dependent fluorescence behavior and high fluorescent chemical stability. Based on the fantastic optical behavior of the CDs, they were utilized as probes for fluorescent determination of copper ions (Cu2+). In the range of 1-10 µmol L-1, the fluorescent intensity of BCDs and GCDs decreased linearly with the increase of Cu2+ concentration; the linear correlation coefficient reached 0.9951 and 0.9982, and the limit of detection (LOD) was 0.74 and 1.08 µmol L-1, respectively. In addition, these CDs remained stable in 0.001-0.1 mmol L-1 salt solutions; BCDs were more stable in the neutral pH range, but GCDs were more stable in neutral to alkaline conditions. The CDs prepared from GB are not only simple and low-cost, but also can realize the comprehensive utilization of biomass.

Preparation and chromatographic evaluation of a mixed polymer brush-silica stationary phase with temperature-sensitive property.

In this study, a developed chromatographic stationary phase combines the high selectivity of mixed-mode retention with a temperature-responsive property to boost separation efficiency. Copolymer brushes were grafted onto silica gels through surface initiated-atom transfer radical polymerization by polymerizing two types of monomer, temperature-responsive vinylcaprolactam (VCl) and quinine (Qun) containing benzopyridine, a tertiary ammonium positive center, and hydroxyl groups. The obtained silica@poly(Qun-co-VCl) stationary phases were packed as a chromatographic column, and the retention behavior of hydrophobic polycyclic aromatics, highly polar nucleosides, charged organic acids and ß-agonists was studied for this column under different separation modes. The ability to separate different types of analyte shows that the silica@poly(Qun-co-VCl) column provides multiple hydrophobic, hydrophilic and electrostatic interactions toward analytes, achieving the separation of various compounds in one column. In addition, temperature-dependent resolution of polycyclic aromatics, nucleosides, organic acids and ß-agonists was investigated using modulation of the column temperature, and the column exhibited adjustable separation selectivity by simply changing the column temperature. These results demonstrate that the grafting of copolymer brushes on a silica surface, consisting of temperature-responsive poly-VCl and multifunctional groups of poly-Qun, is useful as a mixed-mode chromatographic stationary phase for thermally-modulated multiple interactions. Additionally, this column was also used for the quantitative detection of uridine and inosine from cordyceps.

Triblock copolymer-grafted restricted access materials with zwitterionic polymer outer layers for highly efficient extraction of fluoroquinolones and exclusion of proteins.

High-selectivity and high-exclusion restricted access materials (RAMs) benefit the analysis of biological samples. Herein, triblock copolymer-functionalized poly(4-vinylbenzyl chloride-co-divinylbenzene) (PVBC/DVB) microspheres were prepared via the sequential surface-initiated atom radical polymerization of hydrophobic styrene (St), ionic vinylimidazole (VIm), and zwitterionic sulfobetaine methacrylate (SBMA), affording RAMs with multiple interaction-adsorption sites and zwitterionic polymer exclusion sites on the internal and external surfaces of PVBC/DVB. The preferential extraction of fluoroquinolones (FQs) is realized based on the hydrophobic/π-π/ion exchange interactions due to the grafted poly-St-VIm, and the zwitterionic poly-SBMA block in the triblock copolymers can efficiently exclude various proteins. A sensitive detection method for FQs in chicken was established by solid phase extraction with RAMs as adsorbent combined with UPLC-MS/MS, achieving wide linearity (2.0-200.0 ng mL-1), low limit of detection (0.5 µg kg-1) and limit of quantification (1.5 µg kg-1), and good inter- and intraday precision with satisfactory recoveries (104.1%-117.7% and 115.3%-121.2% with RSDs < 12%).

Preparation of reversed-phase/boronate affinity mixed-mode restricted access materials with zwitterionic polymer outer layers and its extraction properties.

High-selectivity and high-exclusion restricted access materials (RAMs) benefit the demands of complex biological samples. In this study, mixed-mode-adsorption RAMs bearing zwitterionic polymer brushes as their outer layers were proposed. The reversed-phase/bronate affinity (RP/BA) mixed-mode adsorption layers on the surface of the silica gel were first formed by surface-initiated atom transfer radical polymerization (SI-ATRP) employing styrene (St) and 4-vinylphenylboronic acid (4-VPBA) as comonomers Afterward, zwitterionic poly(sulfobetaine methacrylate, SBMA) was grafted via another SI-ATRP reaction to establish the external hydrophilic layer. The selectivity of the developed Sil@poly(St-co-4-VPBA)@poly(SBMA) RAMs was examined employing different analytes (benzenes, tetracyclines, neurotransmitters, ß-agonists, and their structural analogs), the results revealed the preferential adsorption of substances bearing phenyl and cis-diol groups owing to the multiple interactions (hydrophobic, π-π and BA forces) caused by the RAMs with RP/BA mixed-mode adsorption mechanism. On the other hand, the synergistic effect of the strong-hydrophilicity and high-density zwitterionic poly(SBMA) could efficiently promote the exclusion of RAMs. Moreover, the experimental data revealed that > 99% of bovine serum albumin (BSA, 1 g L-1) could be excluded, although the tetracycline (50 µg L-1) was completely adsorbed, indicating the maximized adsorption capacity of the RAMs toward small molecules after the efficient exclusion of protein interference. Solid-phase extraction (SPE) employing the developed Sil@poly(St-co-4-VPBA)@poly(SBMA) RAM coupled with high-performance liquid chromatography (HPLC) was successfully employed to determine the tetracycline content of a milk sample. The established method exhibited satisfactory linearity (10-700 µg L-1), high recovery (93.1%-108.6%) and good precision (2.6%-8.4%). Finally, our proposed method for synthesizing RAMs could efficiently boost the adsorption selectivity and restricted access function of RAMs, thereby promoting their application in analyzing biological samples.

Enantioseparation in high performance liquid chromatography: preparation and evaluation of a vancomycin-based chiral stationary phase via surface-initiated atom transfer radical polymerization.

A chromatographic technique based on a chiral stationary phase (CSP) has been explored for enantioseparation. Herein, poly(glycidyl methacrylate) (poly(GMA)) brushes were grafted on the surface of silica gel via surface-initiated atom transfer radical polymerization (SI-ATRP), followed by the introduction of vancomycin as a chiral selector. The as-synthesized material was characterized by elemental analysis, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and thermogravimetric analysis (TGA), proving the formation of vancomycin-immobilized brushes. Then the resulting CSP was explored to separate 7 racemic drugs (bicalutamide, 1-benzyl-5-phenylbarbituric acid, chlorpheniramine maleate, fluoxetine hydrochloride, verapamil hydrochloride, benzoxazocine hydrochloride and isoprenaline hydrochloride) in high performance liquid chromatography (HPLC). Several factors affecting the enantioseparation performance of the vancomycin-immobilized CSP, including the triethylamine (TEA) content in the buffer, pH value, content of organic solvent in the mobile phase, flow rate and injection volume, were mainly optimized. Under the optimal conditions, baseline separation of fluoxetine hydrochloride (RS = 2.52) was achieved, which was better than that on a commercial Chirobiotic V column, while enantioseparation of bicalutamide (RS = 1.01), chlorpheniramine maleate (RS = 0.77), 1-benzyl-5-phenylbarbituric acid (RS = 0.67), isoprenaline hydrochloride (RS = 0.73), verapamil hydrochloride (RS = 0.91) and benzoxazocine hydrochloride (RS = 1.03) was partly achieved. It was concluded that SI-ATRP is a robust way to fabricate vancomycin-based CSPs for enantioseparation.