Polymer brush grafted immobilized metal ion affinity adsorbent based on polydopamine/polyethyleneimine-coated magnetic graphene oxide for selective enrichment of cytokinins in plants.

An immobilized metal affinity (IMAC) adsorbent was prepared for selective enrichment of adenine type CKs, via grafting polymer chain pendant with iminodiacetic acid (IDA) from polydopamine (PDA)/polyethyleneimine (PEI)-coated magnetic graphene oxide (magGO) via surface-initiated-atom transfer radical polymerization (SI-ATRP). The prepared IMAC sorbent exhibited remarkable adsorption performances and good selectivity for adenine-type CKs and was utilized as a sorbent of magnetic solid-phase extraction (MSPE) for effective enrichment of four adenine-type CKs in bean sprouts. Under the optimized extraction conditions, an analytical method for four adenine type CKs in bean sprouts was established by combining the MSPE combined with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The recoveries of the analytes were between 80.4 ± 1.9% and 114.6 ± 1.5% (n = 3). The limits of detection (LODs) range from 0.63 to 2.30 pg⋅mL-1. The relative standard deviations of intra-day and inter-day were less than 12.6%. The established method was successfully applied to the selective extraction and sensitive detection of trace adenine-type CKs in plant samples.

Adjusting the chromatographic properties of poly(ionic liquid)-modified stationary phases by substitution on the imidazolium cation.

Poly(ionic liquid)-modified stationary phases can have multiple interactions with solutes. However, in most stationary phases, separation selectivity is adjusted by changing the poly(ionic liquid) anions. In this work, two poly(ionic liquid)-modified silica stationary phases were prepared by introducing the cyano or tetrazolyl group on the pendant imidazolium cation on the polymer chains. Various analytes were selected to investigate their mechanism of retention in the stationary phases using different mobile phases. Two poly(ionic liquid)-modified stationary phases can provide various interactions toward solutes. Compared to the cyano-functionalized poly(ionic liquid) stationary phase, the tetrazolyl-functionalized poly(ionic liquid) stationary phase provides additional cation-exchange and π-π interactions, resulting in different separation selectivity toward analytes. Finally, applicability of the developed stationary phases was demonstrated by the efficient separation of nonsteroidal anti-inflammatory drugs.

Preparation of bottlebrush polymer-modified magnetic graphene as immobilized metal ion affinity adsorbent for purification of hemoglobin from blood samples.

An immobilized metal affinity (IMA) adsorbent was prepared by grafting bottlebrush polymer pendant with iminodiacetic acid (IDA) from the surface of polydopamine (PDA)-coated magnetic graphene oxide (magGO), via surface-initiated atom transfer radical polymerization (SI-ATRP). Poly(hydroxyethyl methacrylate) (PHEMA) was grafted firstly from the PDA-coated magGO as the backbone, and then poly(glycidyl methacrylate) was grafted from the PHEMA chains via the second SI-ATRP to afford the bottlebrush polymer-grafted magGO Thereafter, IDA was anchored on the nanocomposites to produce the IMA adsorbent after chelating copper ions. The adsorbent was characterized by various physical and physicochemical methods. Its adsorption properties were evaluated by using histidine-rich proteins (bovine hemoglobin, BHb) and other proteins (lysozyme and cytochrome-C). The results show that its maximum adsorption capacity to BHb was 378.6 mg g-1, and the adsorption equilibrium can be quickly reached within 1 h. The adsorbent has excellent reproducibility and reusability. It has been applied to selectively purify hemoglobin from human whole blood, indicating its potential in practical applications. Graphical abstract.

A magnetic adsorbent grafted with pendant naphthyl polymer brush for enrichment of the nonsteroidal anti-inflammatory drugs indomethacin and diclofenac.

Poly(2-naphthyl acrylate) was first grafted onto silica-coated magnetic nanoparticles by surface-initiated atom transfer radical polymerization to prepare a reversed-phase magnetic adsorbent. The resulting polymer brush displays enhanced extraction efficiency by offering active sites on the surfaces of adsorbent. It was applied to the preconcentration of the non-steroidal antiinflammatory drugs (NSAIDs) indomethacin (InDo) and diclofenac (DIC). These drugs interact with the sorbent through hydrophobic and π-interactions, and via electrostatic attraction. By coupling the magnetic solid-phase extraction with HPLC, a method for analysis of InDo and DIC in the environmental water samples was established. The limits of detection range from 0.62 to 0.64 ng·mL-1, and the relative standard deviations for intra-and inter-day analyses of spiked water samples are <11.9%, and relative recoveries are between 62.1 and 96.7%. Graphical abstract A reversed-phase magnetic adsorbent was prepared by grafting poly(2-naphthyl acrylate) brush on the surface of silica coated magnetic nanoparticles. Due to the two conjugated aromatic rings of the monomer, the polymer brush can effectively extract non-steroidal anti-inflammatory drugs through strong π- and hydrophobic interactions.

Nitrogen-doped magnetic porous carbon nanospheres derived from dual templates-induced mesoporous polydopamine coated Fe3O4 for efficient extraction and sensitive determination of volatile nitrosamines by gas chromatography-mass spectroscopy.

N-nitrosamines (NAs) are highly carcinogenic compounds commonly found in food, beverages, and consumer products. Due to their wide polarity range, it is challenging to find a suitable carbon adsorbent that can simultaneously adsorb and enrich both polar and nonpolar NAs with good recovery. In this study, nitrogen-doped magnetic mesoporous carbon nanospheres (M-MCN) were prepared and employed as an adsorbent for magnetic solid-phase extraction (MSPE) to extract and concentrate four NAs. The introduction of nitrogen functional groups enhanced the hydrophilicity of the carbon material, allowing M-MCN to achieve a balance between hydrophilicity and hydrophobicity, resulting in good recovery for both polar and nonpolar NAs. A method combining MSPE with gas chromatography-mass spectrometry (GC-MS) was developed for the determination of NAs in processed meat and alcoholic beverages. The method exhibited a good linear range (1-100 ng g-1, r2 > 0.9967) and trace-level detection (0.53-6.6 ng g-1). The recovery rates for the four NAs ranged between 85.7 and 110.7 %, with intra-day precision expressed as relative standard deviation (RSD) between 4.1 and 10.7 %, and inter-day precision between 4.8 and 12.9 %. The results demonstrated not only good accuracy and precision but also provided a new adsorbent for the enrichment of trace-level NAs in processed meat and alcoholic beverage samples.

Molecular bottlebrush polymer modified magnetic adsorbents with high physicochemical selectivity and unique shape selectivity.

A molecular bottlebrush functionalized magnetic adsorbent (magGO@bottlebrush) was fabricated in this work. Poly(hydroxyethyl methacrylate) (PHEMA) was first grafted from polydopamine coated magnetic graphene oxide via surface-initiated atom transfer radical polymerization (SI-ATRP) to produce the backbone of the molecular bottlebrush. Further modification was followed by grafting poly(styrene) via a second SI-ATRP from the PHEMA chains to yield the magGO@bottlebrush. Multiple interactions including hydrophobic, π-π stacking and π-π electron-donor-acceptor interactions greatly contributed to the solute retention. The adsorbent possessed unique shape selectivity, it provided high affinity to non-planar and non-linear compounds. Profiting from densely grafted phenyl and carbonyl groups on the adsorbent, multivalent interactions were exploited to enhance the selectivity for analytes with multiple recognition motifs. Bisphenol A (BPA) was chosen as a model analyte to test real applications of the adsorbent, considering its structural features. The adsorbent owns high adsorption capacity to BPA, and can be readily used for rapid and efficient enrichment of trace BPA from water samples.

Preparation of hydrophilic interaction/ion-exchange mixed-mode chromatographic stationary phase with adjustable selectivity by controlling different ratios of the co-monomers.

Development of mixed-mode chromatography (MMC) stationary phase with adjustable selectivity is beneficial to meet the needs of complex samples. In this work, surface-initiated atom transfer radical polymerization (SI-ATRP) using the mixture of two functional monomers was proposed as a new preparation strategy for MMC stationary phase with adjustable selectivity. The mixture of sodium 4-styrenesulfonate (NASS) and dimethylaminoethyl methacrylate (DMAEMA) underwent SI-ATRP to bond poly(NASS-co-DMAEMA) on the surface of silica to prepare hydrophilic interaction/ion-exchange mixed-mode stationary phase. Various analytes (neutral, acidic, basic analytes and strong polar nucleosides) were employed to investigate the retention behaviors. The influences of water content and pH of the mobile phase on the retention validated the mixed-mode retention mechanisms of HILIC and ion-exchange. The charge and polarity of stationary phase as well as the separation selectivity were conveniently manipulated by the ratio of NASS to DMAEMA monomer, and the use of DMAEMA in the mixture additionally endowed the column with the temperature-responsive characteristics. Moreover, the application of the developed column was demonstrated by the successful separation of nucleosides, ß-agonists and safflower injection. In a word, the proposed strategy can be potentially applied in the controllable preparation of MMC stationary phase with adjustable selectivity.

Preparation of a novel Zr(4+)-immobilized metal affinity membrane for selective adsorption of phosphoprotein.

In this study, a novel phosphate-Zr(4+) immobilized metal affinity membrane (IMAM) was prepared based on the surface initiated-atom transfer radical polymerization technique for the selective adsorption of phosphoprotein. The adsorption capacity and selectivity of the phosphate-Zr(4+) IMAM were evaluated by using the mixture of standard phosphoproteins (ß-casein, ovalbumin) and nonphosphoproteins (bovine serum albumin and lysozyme) as model samples. The adsorption isotherms and competitive adsorption results demonstrated that the phosphate-Zr(4+) IMAM had higher binding capacity and selectivity for phosphoproteins over nonphosphoproteins. Moreover, the phosphate-Zr(4+) IMAM exhibited good re-usability and re-productivity. Finally, the phosphate-Zr(4+) IMAM was applied to separate phosphoprotein from real samples with high purity. Therefore, the as-prepared phosphate-Zr(4+) IMAM could be a promising affinity material for the efficient enrichment of phosphoprotein from complex bio-samples.

Preparation of hydrophobic interaction chromatographic packings based on monodisperse poly(glycidylmethacrylate-co-ethylenedimethacrylate) beads and their application.

The monodisperse, poly(glycidylmethacrylate-co-ethylenedimethacrylate) beads with macroporous in the range of 8.0-12.0 microm were prepared by a single-step swelling and polymerization method. The seed particles prepared by dispersion polymerization exhibited good absorption of the monomer phase. The pore size distribution of the beads was evaluated by gel permeation chromatography and mercury instrusion method. Based on this media, a hydrophobic interaction chromatographic (HIC) stationary phase for HPLC was synthesized by a new chemically modified method. The prepared resin has advantages for biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery and good resolution for proteins. The dynamic protein loading capacity of the synthesized HIC packings was 40.0 mg/ml. Six proteins were fast separated in less than 8.0 min using the synthesized HIC stationary phase. The HIC resin was firstly used for the purification and simultaneous renaturation of recombinant human interferon-gamma (rhIFN-gamma) in the extract solution containing 7.0 mol/l guanidine hydrochloride with only one step. The purity and specific bioactivity of the purified of rhIFN-gamma was found more than 95% and 1.3 x 10(8) IU/mg, respectively.

Immobilization of 5-aminopyridine-2-tetrazole on cross-linked polystyrene for the preparation of a new adsorbent to remove heavy metal ions from aqueous solution.

Novel 5-aminopyridine-2-tetrazole-functionalized polystyrene resin (APTZ-PS) was prepared by anchoring 5-aminopyridine-2-carbonitrile onto chloromethylated polystyrene beads (CMPS) and subsequently using the cyano-tetrazole conversion reaction. The APTZ-PS resin was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and specific surface area and pore size analyses. The adsorption experiments of the prepared resin for heavy metal ions were conducted by batch methods. The effects of the experimental conditions, such as pH, contact time and initial metal ion concentration on the adsorption properties of Cu(II), Pb(II) and Hg(II) were investigated. The results showed that the resin possessed perfect adsorption capacities for Cu(II), Pb(II) and Hg(II), and the selectivity was different from the commonly used iminodiacetic acid-chelating resin. The sorption kinetics of the three metal ions followed the pseudo-second-order equation. The adsorption isotherms for Cu(II) and Pb(II) could be better fitted by the Langmuir model than the Freundlich model, whereas the Freundlich model was the best for the Hg(II) ion. Even after five consecutive adsorption-desorption cycles, no obvious change in the adsorption capacity of the resin was found, which implied that the APTZ-PS resin was suitable for the efficient removal of heavy metal ions from aqueous solution.