Porous ß-cyclodextrin polymers for rapid and efficient removal of organic micropollutants from water: The role of sulfonation and porosity on adsorption performance.

Removal of organic micropollutants (OMPs) from water, especially hydrophilic and ionized ones, is challenging for water remediation. Herein, porous ß-cyclodextrin polymers (PCPs) with tailored functionalization were prepared based on molecular expansion strategy and sulfonation. Partially benzylated ß-cyclodextrin was knotted by external crosslinker to form PCP1, and knotting PCP1 by expansion molecule generated PCP2. PCP1 and PCP2 were sulfonated to achieve PCP1-SO3H and PCP2-SO3H. Based on systematical adsorption evaluation toward multiple categories of OMPs, it was found that the introduced strong polar -SO3H group could bring strong hydrogen bonding and electrostatic interactions. PCP2 showed the highest surface (998.97 m2/g) displayed more excellent adsorption performance toward neutral and anionic OMPs, and the adsorption mechanism for this property of PCP2 was dominated by hydrophobic interactions. In addition, the PCP1-SO3H with the lowest surface area (39.75 m2/g) rather than PCP2-SO3H with higher surface (519.28 m2/g) exhibited more superior adsorption towards hydrophilic and cationic OMPs, benefiting by hydrogen bonding and electrostatic interactions as well as appropriate porosity. These results not only confirmed the performance enhancement of PCPs through the integration of novel preparation strategy, but also provided fundamental guidance for PCPs design for water remediation.

Tetraethylenepentamine-derived carbon dots and tetraethylenepentamine co-immobilized silica stationary phase for hydrophilic interaction chromatography.

In this work, tetraethylenepentamine (TEPA) was used as precursor and reaction medium to prepare tetraethylenepentamine-functionalized carbon dots (TEPACDs), the resultant mixture was subsequently silanized and then grafted on the surface of bare silica. The obtained tetraethylenepentamine-functionalized carbon dots and tetraethylenepentamine co-modified silica stationary phase (Sil-TEPA/CDs) was characterized by multiple ways, such as Fourier transformed infrared spectroscopy (FTIR), elemental analysis and transmission electron microscope, which revealed the successful preparation of the mixed stationary phase and higher density of functional groups on co-modified stationary phase than precursor single-modified stationary phase. The synergistic effect of TEPACDs and TEPA was proved by comparing the separation performance of Sil-TEPA/CDs and Sil-TEPA toward amino acids, nucleosides, and nucleobases, which distinctly enhanced the selectivity of Sil-TEPA/CDs. Thus, 12 nucleosides and nucleobases and 11 amino acids was nicely separated on Sil-TEPA/CDs. By study the influences of the changes of mobile phase composition, mobile phase buffer concentration and buffer pH on the retention behaviors of Sil-TEPA and Sil-TEPA/CDs, it was found that both hydrophilic partitioning and adsorption of analytes on Sil-TEPA/CDs were enhanced benefit from the co-existence of TEPA and TEPACDs, which provided the analytes better separation performance. By comparing the column quality of Sil-TEPA/CDs with four commercially available columns, Sil-TEPA/CDs exhibited the best peak asymmetry of 0.98, and second best column efficiency of 43895 m-1 using guanosine as analyte. The RSD (n = 9) of the retention times of five selected analytes on Sil-TEPA/CDs were within 0.30-0.61% during 40 h of continuously elution, which implied excellent stability of prepared packing material.

Preparation of monodisperse, restricted-access, media-molecularly imprinted polymers using bi-functional monomers for solid-phase extraction of sarafloxacin from complex samples.

Monodisperse restricted-access media bi-functional monomers with molecularly imprinted polymers (RAM-MIPs) were constructed using surface-initiated atom transfer radical polymerization. They were used as solid-phase extraction (SPE) adsorbents to enrich sarafloxacin (SAR) residues from egg samples, and influences on their performance were investigated. Optimum synthesis of RAM-MIPs was achieved by combining a bi-functional monomer (4-vinylpyridine-co-methacrylic acid, 1:3) with an 8:1:32:8 ratio of a template molecule, cross-linker, and restricted-access functional monomer. The SAR imprinting factor of RAM-MIPs was 6.05 and the selectivity coefficient between SAR and other fluoroquinolones was 1.86-2.64. Compared with traditional MIPs, the RAM-MIPs showed better SAR enrichment and selectivity during extraction of a complex protein-containing solution. Empty SPE cartridges were filled with RAM-MIP microspheres as SPE adsorbents. The limit of quantitation for SAR was 4.23 ng g-1 (signal-to-noise ratio = 10) and the mean SAR recovery from spiked egg samples was 94.0-101.3%. Intra-day and inter-day relative standard deviations were 1.1-9% and 1.5-3.3%, respectively.

Synthesis of monodisperse magnetic restricted microspheres for recognition of thiamphenicol in milk.

Taking thiamphenicol as the research object, a new type of magnetic restricted access molecularly imprinted polymer (RAM-MMIP) with specific recognition was prepared by a one-step swelling method. The polymer microspheres were characterized and analyzed by scanning electron microscopy, X-ray diffraction, elemental analysis, contact angle measurement and vibrating sample magnetometry. When the ratio of template molecule, functional monomer and cross linking agent was 1 : 4 : 8, the adsorption capacity reached the maximum. Under these conditions, RAM-MIP magnetic solid phase extraction (M-SPE) was combined with HPLC to analyze thiamphenicol in milk samples. Satisfactory linear correlation (R 2 > 0.9977), good detection limit (LOD: 10.4 µg L-1), high recovery rate (96.5-101.1%), and relative standard deviation (RSD: 2.8-3.8%) were obtained. Therefore, our synthesized material can be used for the analysis of TAP in complex milk samples, and has broad application value.

Restricted access media-imprinted nanomaterials based on a metal-organic framework for highly selective extraction of fluoroquinolones in milk and river water.

A new type of restricted access media-imprinted nanomaterials (RAM-MIPs) were successfully prepared on the surface of metal-organic framework by reversible addition fragmentation chain transfer polymerization technology. Then it was applied as a dispersed solid phase extraction (DSPE) material in analysis of fluoroquinolones (ofloxacin, pefloxacin, norfloxacin, enrofloxacin and gatifloxacin) in untreated milk and river water by HPLC-UV detection. The resulted material has a good binding amounts (60.81 mg g-1), rapid binding kinetic (15 min) and satisfactory selectivity as well as has a good ability to eliminate matrix interference. Several major factors affecting DSPE efficiency, pH of sample solution, dosage of RAM-MIPs, adsorption time and volume ratios of elution solvent were primarily optimized. In optimization conditions, RAM-MIPs-DSPE was combined with HPLC-UV to enrich fluoroquinolones in untreated milk and river water, achieving satisfactory linear correlation (R2 > 0.9988), good limits of detection (LOD, 1.02-3.15 µg L-1 for milk and 0.93-2.87 µg L-1 for river water) and better recoveries (80.7-103.5% and 85.1-105.9% with relative standard deviation (RSD) of not higher than 5.3% and 4.7% for milk and river water samples, respectively). The research results illustrate that it provides a simple and efficient method for the direct detection of FQs in complex samples.

Monodisperse restricted access material with molecularly imprinted surface for selective solid-phase extraction of 17ß-estradiol from milk.

In this study, novel monodisperse restricted access media-molecularly imprinted polymers were successfully prepared by surface initiated reversible addition-fragmentation chain transfer polymerization using monodisperse crosslinked poly (glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres as the carrier and acryloyl chloride-modified ß-cyclodextrin as the hydrophilic functional monomer. The surface morphology, protein exclusion, and adsorption properties of the molecularly imprinted polymers were investigated. The results show that the material has excellent monodispersity and hydrophilicity, and simultaneously exhibit high adsorption capacity, fast binding kinetics, high selectivity, and significant thermal stability. The molecularly imprinted polymers as dispersive solid-phase extraction adsorbent combined with reversed-phase high-performance liquid chromatography was used to selectively enrich, separate, and analyze trace 17ß-estradiol in milk samples. The recovery of 17ß-estradiol is 88-95% with relative standard deviation of <4%, and the limits of detection and quantification of this method are 2.08 and 9.29 µg/L, respectively. The novel restricted access media-molecularly imprinted polymer adsorbents provide an effective method for the selective extraction and detection of 17ß-estradiol directly from complex samples.

Glucose-based carbon dots-modified silica stationary phase for hydrophilic interaction chromatography.

A new stationary phase based on glucose-derived carbon dots-modified on silica (Sil-Glc-CDs) was prepared and applied in hydrophilic interaction chromatography (HILIC). The Sil-Glc-CDs column showed better retention ability and separation selectivity toward polar analytes, including amino acids, saccharides, ginsenosides, antibiotics, nucleosides, and nucleobases when compared with a commercial HILIC column and a home-made glucose-modified silica (Sil-Glc) column. The effect of the organic phase ratio, salt concentration, pH and column temperature on chromatographic retention behavior was investigated. In addition, the column exhibited good stability and column-to-column reproducibility (RSDs 0.80-1.97%, n = 3). Particularly, this column was successfully applied for the determination of the concentration of glucose (2.2 mg mL-1) and fructose (3.4 mg mL-1) in the goji berry solution.

Two copolymer-grafted silica stationary phases prepared by surface thiol-ene click reaction in deep eutectic solvents for hydrophilic interaction chromatography.

Two new copolymer-grafted silica stationary phases were prepared and employed in hydrophilic interaction chromatography (HILIC). 2-(Dimethylamino)ethyl methacrylate (DMAEMA) are copolymerized with itaconic acid (IA) and acrylic acid (AA) respectively, via thiol-ene click reaction on silica surface with deep eutectic solvents (DES) as new solvents. The obtained poly(DMAEMA-co-itaconic acid)-grafted silica (Sil-PDM-PIA) and poly(DMAEMA-co-acrylic acid)-grafted silica (Sil-PDM-PAA) were characterized by Fourier transform infrared spectroscopy, elemental analysis and solid-state 13C NMR spectra. Their hydrophilic interaction performances were evaluated by separating nucleosides, nucleobases, saccharides, and amino acids. Compared with previous reported poly(itaconic acid)-grafted silica (Sil-PIA) and poly(acrylic acid)-grafted silica (Sil-PAA) stationary phases, these two new copolymer-grafted silica performed higher selectivity and better separation for polar analytes in HILIC.

Restricted access magnetic imprinted microspheres for directly selective extraction of tetracycline veterinary drugs from complex samples.

A novel restricted access media-magnetic molecularly imprinted polymers (RAM-MMIPs) was prepared as magnetic-solid phase extraction (M-SPE) material for tetracyclines (TCs). The RAM-MMIPs can not only specifically adsorb target molecules in samples, but also effectively eliminate the interference of protein macromolecules. The protein exclusion rate is 99.4%. Besides, RAM-MMIPs have a uniform imprinted and hydrophilic layer (600 nm), rapid binding kinetic (35 min), high selectivity and larger adsorption capacity. The M-SPE was coupled with HPLC/UV to extract TCs from untreated milk and egg samples, and several major factors affecting M-SPE efficiency were optimized. Under optimized conditions, the developed method achieved good linearity (R2>0.9989), lower limits of detection (LOD) and higher recoveries of TCs. For milk samples, the LOD is 1.03-1.31 µg L-1 and the recovery is 86.7% to 98.6% with relative standard deviation (RSD) of 1.4-5.7%. For the egg samples, the LOD, recovery and RSD are 2.21-2.67 µg L-1, 84.2-96.5% and 1.7-5.9%, respectively. Consequently, this work provides an improved strategy for the selective extraction and detection of target molecules directly from complex samples with proteins.

Preparation of restricted access media molecularly imprinted polymers for efficient separation and enrichment ofloxacin in bovine serum samples.

We prepared ofloxacin restricted access media molecularly imprinted polymers using surface-initiated atom transfer radical polymerization on the surface of brominated silica gel using ofloxacin as a template molecule, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a crosslinking agent. We then characterized and studied the surface morphology and adsorption properties of the polymer. Experimental results show that saturation is reached within 25 min, and that the saturated adsorption capacity was 80.67 mg/g and the imprinting factor was 1.94. Our findings also showed that the polymer surface had good hydrophilicity and an excellent protein exclusion rate, which was 98.49%. The restricted access media molecularly imprinted polymers were then successfully applied to the enrichment and separation of ofloxacin in bovine serum. When combined with high-performance liquid chromatography, and the average recovery of ofloxacin was 95.6%, and the relative standard deviation was in the range of 2.47-3.38%. In a word, the restricted access media molecularly imprinted polymers is a method that involves a simple preparation procedure that results in excellent performance, which is a great improvement in the speed of detection of antibiotics. These qualities are what bestow upon this method its great potential for broad application.

Polyethyleneimine-functionalized carbon dots and their precursor co-immobilized on silica for hydrophilic interaction chromatography.

A new strategy based on synergistic effect of the carbon dots and their precursor was proposed to enhance the selectivity of hydrophilic interaction liquid chromatography (HILIC). In this work, polyethyleneimine (PEI) and PEI-functionalized carbon dots (PEICDs) mix-grafted silica packing material was prepared to act as a novel HILIC stationary phase. Both inner and outer surface of the porous silica are decorated with the mixture of PEI and carbon dots. This stationary phase, namely Sil-PEI/CDs, demonstrate enhanced retention ability and selectivity toward polar analytes, with which 11 nucleosides and nucleobases and 9 ginsenosides can be nicely separated. The Sil-PEI/CDs (RSD 0.12% - 0.54%) exhibited even better stability than the traditional PEI modified stationary phase (RSD 0.39% - 0.87%) within 40 h of continuously elution. And excellent column efficiency was observed from Sil-PEI/CDs (∼65,000 plates/m for cytidine). The strategy of mixed stabilization revealed a new method to prepare good performanced carbon dots based chromatographic column.

Poly(itaconic acid)-grafted silica stationary phase prepared in deep eutectic solvents and its unique performance in hydrophilic interaction chromatography.

In this study, a new stationary phase based on poly(itaconic acid)-grafted silica (Sil-PIA) were synthesized in deep eutectic solvents (DESs) and characterized in detail. Itaconic acid was homopolymerized on silica via surface radical chain-transfer reaction using DESs as a new kind of green solvents. Sil-PIA were obtained and characterized by Fourier transform infrared spectroscopy, elemental analysis and scanning electron microscopy. The retention changes of nucleosides and nucleobases on the columns was studied under different chromatographic conditions including salt concentration, acetonitrile content, mobile phase pH, and column temperature. Compared with previous reported poly(acrylic acid)-grafted silica (Sil-PAA) stationary phase, Sil-PIA possesses shorter retention time but similar or higher selectivity for the separation of most polar compounds such as bases, nucleosides, amino acids, and saccharides in hydrophilic interaction chromatography. Most importantly, Sil-PIA presents very good performance at the separation of eleven ginsenosides using isocratic elution in hydrophilic chromatography.

Surface radical chain-transfer reaction in deep eutectic solvents for preparation of silica-grafted stationary phases in hydrophilic interaction chromatography.

In this paper, deep eutectic solvents (DESs) were firstly used as new and green solvents for the preparation of polymer-grafted silica stationary phases. 1-Vinylimidazole and acrylic acid were homopolymerized and copolymerized on silica via surface radical chain-transfer reaction in the DESs. Three stationary phases including poly(1-vinylimidazole)-, poly(acrylic acid)-, poly(1-vinylimidazole-co-acrylic acid)-grafted silica were obtained and characterized by elemental analysis and Fourier transform infrared spectroscopy. Their hydrophilic interaction chromatographic properties were investigated for separation of nucleosides, nucleobases, saccharides and amino acids. The retention changes of nucleosides and nucleobases on these columns were investigated under different chromatographic conditions including acetonitrile content, salt concentration, pH of mobile phase and column temperature. The repeatability of these columns was also investigated. The results demonstrate that DESs can be used as new media for the synthesis of silica-based stationary phases by homopolymerization and copolymerization on the surface of porous silica particles.

Preparation and characterization of carbon dot-decorated silica stationary phase in deep eutectic solvents for hydrophilic interaction chromatography.

In this paper, N-doped carbon dots (NCDs) were successfully decorated on the spherical porous silica surface in deep eutectic solvents (DESs) as a novel class of green solvents. The appropriate density and hydrophility of DESs guaranteed the fine dispersibility of silica particles and NCDs, resulting in a homogeneous and thin layer of NCDs immobilization. As compared with traditional organic solvents (DMF and THF), higher surface coverage was obtained in the medium of DES, proving its feasibility as a new kind of alternative solvent for hydrophilic nanomaterial-based surface modification of silica spheres. The resulting NCDs-decorated silica particles (Sil-NCDs) were characterized in detail and packed into chromatographic columns to study their initial feasibility as adsorbent material for liquid chromatography. The resultant packing materials demonstrate a selective behavior for polar compounds in hydrophilic interaction liquid chromatography (HILIC) mode. This work gives a typical example of using carbon dots as stationary phase component, and such material is hopeful to be used in other research fields such as solid absorbents, recycling catalysts, and solid-state electrochemistry etc. Graphical Abstract N-doped carbon dots (NCDs) were successfully coupled on the surface of porous silica spheres in a green strategy using deep eutectic solvents (DES) as media for HILIC.

[Determination of dioxane residue in cosmetics by isotope dilution-headspace gas chromatography-mass spectrometry].

A comprehensive analytical method based on isotope dilution-headspace gas chromatography-mass spectrometry was developed for the determination of dioxane residue in the cosmetics. Cosmetic sample (2 g) was placed in a headspace vial. Then, 1 g sodium chloride, 1 mL d8-dioxane solution (20 mg/L) and 9 mL water were added. The vial was sealed and heated at 70 degrees C for 40 min. The qualitative and quantitative analyses were carried out for the analyte in selected ion monitoring (SIM) mode after the chromatographic separation on an HP-5MS column (30 m x 0.25 mm x 0.25 microm). The limit of quantification (LOQ) for dioxane was 2.5 mg/kg. The mean recoveries were 90.5% - 104.0% at the spiked levels of 2.5 - 50 mg/kg with the relative standard deviations in the range of 1.26% - 3.98%. The method is accurate, simple, rapid, and applicable for the inspection of dioxane residue in cosmetics.

[Determination of perfluorooctanoic acid and its salts in the coating layer of nonstick pan by gas chromatography/mass spectrometry coupled with accelerated solvent extractor].

A sensitive, accurate and reproducible analytical method was developed and validated to quantify perfluorooctanoic acid (PFOA) and its salts in the coating layer of nonstick pan. Scraped samples of 0. 5 gram were directly extracted with acetonitrile using an accelerated solvent extractor at 175 degrees C, 10. 3 MPa for 20 min. After rotary evaporation concentration, the PFOA was derivatized with acetyl chloride and methanol at 65 degrees C for 60 min in an air-tight container. An HP-1 MS capillary column (30 m x 0. 25 mm, 0. 33 degrees m) was used for the separation of the analyte. The procedure for the analysis of PFOA was based on gas chromatography interfaced to negative chemical ion mass spectrometry, operated in selected ion monitoring mode. Selected ions of m/z 312, 350, 378, 408, 428 were chosen for quantitation. The assay was linear over the range of 0 - 1 000 microg/L, and the detection limit of PFOA was 5 microg/kg. The precision and recovery were assessed on four different concentrations (5, 20, 100, 500 micro/kg). The recoveries were in the range of 90. 9% - 96. 2% and the relative standard deviations were 1. 37% -6. 37%. The procedure was applied to monitoring PFOA in the coating layer of nonstick pan from supermarket and no positive result was found.