Synthesis of novel ion‐imprinted polymeric nanoparticles based on dibenzo‐21‐crown‐7 for the selective pre‐concentration and recognition of rubidium ions

In this work, we report the first application of ion‐imprinted technology via precipitation polymerization for simple and practical determination of rubidium ions. The rubidium‐ion‐imprinted polymer nanoparticles were prepared using dibenzo‐21‐crown‐7 as a selective ligand, methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross linker, and 2,2′‐azobisisobutyronitrile as radical initiator. The resulting powder material was characterized using scanning electron microscopy, which showed colloidal nanoparticles of 100–200 nm in diameter and slightly irregular in shape. The maximum adsorption capacity of the ion imprinted particles was 63.36 μmol/g. The experimental conditions such as nature and concentration of eluent, pH, adsorption and desorption times, weight of the polymer material, aqueous phase and desorption agent volumes were also studied. Finally, selectivity of the prepared IIP particles toward rubidium ion was investigated in the presence of some foreign metal ions.     

Preparation and Characteristics of Esculin‐Imprinted Polymers

Four molecularly imprinted polymers (MIPs) were prepared in MeOH with esculin (=6,7‐dihydroxycoumarin 6‐(β‐D ‐glucopyranoside)=6‐(β‐D ‐glucopyranosyloxy)‐7‐hydroxy‐2H‐1‐benzopyran‐2‐one) as the imprinted molecule, methacrylic acid (=2‐methylprop‐2‐enoic acid; MAA), acrylamide (=prop‐2‐enamide; AM), 4‐vinylpyridine (=4‐ethenylpyridine; 4‐VP), or 2‐vinylpyridine (=2‐ethenylpyridine; 2‐VP) as the functional monomer, respectively, as well as ethylene glycol dimethacrylate (=2‐methylprop‐2‐enoic acid ethane‐1,2‐diyl ester; EGDMA) as the cross‐linking agent. The interaction between the template and the functional monomers was investigated by fluorescence and UV spectrophotometry, respectively, which revealed the presence of esculin/monomer complexes in the stoichiometric ratio 1 : 2 in the pre‐polymerization mixture. The resultant polymers were studied in equilibrium binding experiments to evaluate the recognition ability and the binding capacity towards esculin. The results showed that MIP₁, prepared with MAA as the functional monomer, exhibited advantageous characteristics of high binding capacity, optimal imprinting effect, and good selectivity towards esculin. The Scatchard analysis indicated that there are two types of binding sites in MIP₁, and its binding parameters including the apparent maximum numbers of binding sites and the dissociation constants were calculated. Finally, by packing an SPE column (SPE=solid‐phase extraction) with MIP₁, the esculin was separated and enriched successfully by this sorbent from samples of Cortex fraxini, and the average recovery was up to 74.7%.     

Theoretical and experimental research on the self‐assembled system of molecularly imprinted polymers formed by salbutamol and methacrylic acid

The quantum chemical method was applied for screening functional monomers in the rational design of salbutamol‐imprinted polymers. Salbutamol was the template molecule, and methacrylic acid was the single functional monomer. The LC‐WPBE/6–31G(d,p) method was used to investigate the geometry optimization, active sites, natural bond orbital charges, binding energies of the imprinted molecule, and solvation energy. The mechanism of action between salbutamol and methacrylic acid was also discussed. The theoretical results show that salbutamol interacts with functional monomers by hydrogen bonds, and the salbutamol‐imprinted polymers with a ratio of 1:4 (salbutamol/methacrylic acid) in acetonitrile had the highest stability. The salbutamol‐imprinted polymers were prepared by precipitation polymerization. The experimental results indicated that the maximum adsorption capacity for salbutamol toward molecularly imprinted polymers was 7.33 mg/g, and the molecularly imprinted polymers had a higher selectivity for salbutamol than for norepinephrine and terbutaline sulfate. Herein, the studies can provide theoretical and experimental references for the salbutamol molecular imprinted system.     

Synthesis and Adsorption Performance of Surface‐Grafted Co(II)‐Imprinted Polymer for Selective Removal of Cobalt

The surface‐grafting ion‐imprinting technology was applied to synthesis of a new Co(II)‐imprinted polymer [Co(II)‐IP], which could be used for selective removal of Co(II) from aqueous solutions. The prepared polymer was characterized by using the infrared spectra (IR), X‐ray diffractometer (XRD), X‐ray energy dispersion spectroscopy (EDS) and scanning electron microscopy (SEM). The maximum adsorption capacity values for the Co(II)‐imprinted polymer and non‐imprinted polymer (NIP) were 22 and 8 mg/g, respectively. The Freundlich equation fitted the adsorption isotherm data well. The applicability of two kinetic models including pseudo‐first‐order and pseudo‐second‐order models was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity, and correlation coefficients. Results suggested that chemical process could be the rate‐limiting step in the adsorption process. And the adsorption of Co(II) on the Co(II)‐imprinted polymer was endothermic. The relative selectivity coefficients of the Co(II)‐imprinted polymer for Co(II)/Pb(II), Co(II)/Cu(II), Co(II)/Ni(II), Co(II)/Sr(II) and Co(II)/Cs(I) were respectively 11.5, 6.1, 13.8, 9.4, and 8.1 times greater than that of the non‐imprinted polymer. Eventually, the desorption conditions of the adsorbed Co(II) from the Co(II)‐imprinted polymer were also studied in batch experiments.     

Ion‐imprinted poly(methyl methacrylate‐vinyl pyrrolidone)/poly(vinylidene fluoride) blending membranes for selective removal of ruthenium(III) from acidic water solutions

While conventional approaches have been studied for removal of ruthenium(III) ions (Ru(III)), this work focuses on the applicability of ion‐imprinted poly(methyl methacrylate‐vinyl pyrrolidone)/poly(vinylidene fluoride) blending membranes (Ru(III)–ion‐imprinted membrane[IIM]) for selective removal of Ru(III) from acidic water solutions. In order to measure the effectiveness of these imprinted membranes, after fabrication, binding experiments were done with aqueous Ru(III) solutions. The results showed that Ru(III)‐IIMs were fabricated successfully at various blending ratios, and their chemical components, microstructures, hydrophilicity, and water fluxes were measured. In pH range 0.5 to 5.0, binding capacity (Q_e) of Ru(III) onto Ru(III)‐IIM increases remarkably with pH and then reaches to a maximum value (53.52 mg/g) at pH 1.5. After that, Q_e gradually decreases. Compared with a nonimprinted membrane, Ru(III)‐IIM demonstrates higher selectivity for Ru(III) at pH 1.5 in the presence of Ni(II) and Cu(II) ions, and its selectivity coefficients for Ru(III)/Ni(II) and Ru(III)/Cu(II) are 3.70 and 3.32, respectively. Also, Ru(III)‐IIM shows a good chemical stability and reusability. C─N and C═O bonds within poly(vinyl pyrrolidone) segments of poly(methyl methacrylate‐vinyl pyrrolidone) (P(MMA‐VP)) participate the uptake of Ru(III). Ru(III)‐IIM exhibited excellent hydrophilicity and Ru(III) selective adsorption ability and reusability and has potential to be used for Ru(III) removal from acidic water solutions.     

Tailor‐made ion‐imprinted polymer based on functionalized graphene oxide for the preconcentration and determination of trace copper in food samples

A tailor‐made Cu(II) ion‐imprinted polymer based on large‐surface‐area graphene oxide sheets has been synthesized for the preconcentration and determination of trace copper from food samples by solid‐phase extraction. Attributed to the ultrahigh surface area and hydrophilicity of graphene oxide, the Cu(II) ion‐imprinted polymer prepared by the surface ion‐imprinting technique exhibited a high binding capacity and a fast adsorption rate under the optimized experimental conditions. In the static adsorption experiments, the maximum adsorption capacity of Cu(II) ion‐imprinted polymer is 109.38 mg/g at 25°C, which is much higher than that of the nonimprinted polymer (32.12 mg/g). Meanwhile, the adsorption is very rapid and equilibrium is reached after approximately 30 min. The adsorption mechanism is found to follow Langmuir adsorption model and the pseudo‐second‐order adsorption process. The Cu(II) ion‐imprinted polymer was used for extracting and detecting Cu(II) in food samples combined with graphite flame atomic adsorption spectrometry with high recoveries in the range of 97.6–103.3%. The relative standard deviation and limit of detection of the method were evaluated as 1.2% and 0.37 μg/L, respectively. The results showed that the novel absorbent can be utilized as an effective material for the selective enrichment and determination of Cu(II) from food samples.     

Via protoporphyrin to the synthesis of levofloxacin‐imprinted polymer

A new molecularly imprinted polymer (MIP) for levofloxacin was prepared by the combined use of methacrylic acid and protoporphyrin as functional monomers. The adsorption properties of resultant imprinted polymers were evaluated by equilibrium rebinding experiments. The highest binding capacity of levofloxacin achieved from the optimized imprinted polymer in acetonitrile was 246.26 µmol/g with an imprinting factor of 2.05. A ?uorescence quenching effect was observed when a protoporphyrin‐based imprinted polymer was incubated in the solutions of levofloxacin. The results indicated that the protoporphyrin‐based MIPs were able to create higher binding cavities for template compared with MIPs using only methacrylic acid as a functional monomer. It should be expected that the cooperative use of the protoporphyrin with supplemental different functional monomers may be an alternative to obtain MIP with the improvement of the selectivity. Copyright © 2010 John Wiley & Sons, Ltd.     

Self‐assembled complexes of poly(acrylic acid) and poly(styrene)‐block‐poly(4‐vinyl pyridine)

Polymer complexes were prepared from high molecular weight poly(acrylic acid) (PAA) and poly(styrene)‐block‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) in dimethyl formamide (DMF). The hydrogen bonding interactions, phase behavior, and morphology of the complexes were investigated using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). In this A‐b‐B/C type block copolymer/homopolymer system, P4VP block of the block copolymer has strong intermolecular interaction with PAA which led to the formation of nanostructured micelles at various PAA concentrations. The pure PS‐b‐P4VP block copolymer showed a cylindrical rodlike morphology. Spherical micelles were observed in the complexes and the size of the micelles increased with increasing PAA concentration. The micelles are composed of hydrogen‐bonded PAA/P4VP core and non‐bonded PS corona. Finally, a model was proposed to explain the microphase morphology of complex based on the experimental results obtained. The selective swelling of the PS‐b‐P4VP block copolymer by PAA resulted in the formation of different micelles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1192–1202, 2009     

Selective 17‐β‐estradiol molecular imprinting

An efficient novel method for the synthesis of a covalent molecularly imprinted polymer (MIP) highly specific to β‐estradiol have been developed. MIP prepared by both covalent and non covalent techniques, demonstrated high selectivity toward β‐estradiol. MIPs were synthesized by radical polymerization of 17‐β‐estradiol 4‐vinyl‐benzene carboxyl or sulfonyl esters used as covalent functional monomers, methacrylic acid as noncovalent functional monomer, ethylene glycol dimethacrylate as crosslinking agent, and acetonitrile as swelling and porogenic component. Almost 35% (w/w) of 17‐β‐estradiol was successfully removed from the polymer network by basic hydrolysis. The binding ability of MIP was 10.73 μg/mg MIP following removal of 17‐β‐estradiol in the 2 mg/mL β‐estradiol solution. Selective rebinding of β‐estradiol toward MIP was tested in the presence of competitive binders including estrone, 19‐nortestosterone, epiandrosterone, and cholesterol. Estrone having closest similar chemical structure to β‐estradiol exhibited only 0.6 μg/mg MIP competitive binding, being exposed to equivalent concentrations. Moreover, other competitive steroids demonstrated negligible affinity toward MIP indicating high selectivity of novel MIP system toward β‐estradiol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5534–5542, 2009     

Metal‐imprinted microsphere prepared by surface template polymerization and its application to chromatography

A metal ion‐imprinted microsphere was prepared by surface molecular template polymerization. Trimethylolpropane trimethacrylate (TRIM), zinc ions, 1,12‐dodecanediol‐O, O′‐diphenyl phosphonic acid (DDDPA) were used as a crosslinking agent, an imprint molecule, and a functional host molecule. The Zn(II)‐imprinted microspheres, which are spherically well‐defined particles, were prepared by using water‐in‐oil‐in‐water (W/O/W) multiple emulsions. The combination of TRIM and DDDPA serves to align the recognition sites resulting in better template sites produced on the polymer surface. We firstly conducted diagnostic zinc‐ and copper‐ion adsorption tests with the Zn(II)‐imprinted and unimprinted microspheres in order to make an assessment on the effectiveness of the molecular imprinting technique. Further, the metal‐imprinted microspheres were applied to the column operation. The separation and recovery of metals were carried out by an adsorption column packed with the Zn(II)‐imprinted microspheres. This performance was compared to that of commercial chelating resins that possess similar phosphoric functional groups. The Zn(II)‐imprinted polymer shows an extremely high selectivity to the imprinted zinc ions compared to that of the commercial chelating resin. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 689–696, 2000     

Side‐chain glycylglycine‐based polymer for simultaneous sensing and removal of copper(II) from aqueous medium

Since glycylglycine (Gly‐Gly) residue in the N‐terminal region of human prion protein, a copper binding protein, binds with Cu(II), N‐terminus Gly‐Gly side‐chain containing water soluble block copolymer was synthesized and used for simultaneous sensing and removal of Cu(II) ion from aqueous medium. The polymer has amide nitrogen atom and ester carbonyl group as potential binding sites in the side‐chain Gly‐Gly pendants. Job's plot experiment confirms 2:1 binding stoichiometry of polymer with Cu(II). This polymer is able to sense parts per billion level of Cu(II) very selectively in an aqueous medium and remove Cu(II) ions quantitatively by precipitating out the Cu(II) via complex formation in the pH range 7–9. The binding mode of polymer with Cu(II) in polymer‐Cu(II) complex was characterized by ¹H NMR, FTIR, and UV–vis spectroscopy. The attachment of Cu(II) in the polymer‐Cu(II) complex was confirmed by cyclic voltammetry experiment. Cu(II) release from the complex was achieved at pH 5 due to the protonation of amide nitrogen atoms in the Gly‐Gly moiety. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 914–921     

Double‐hydrophilic block copolymer for encapsulation and two‐way pH change‐induced release of metalloporphyrins

A double hydrophilic block copolymer composed of poly(acrylic acid) (PAA) and poly(4‐vinyl pyridine) (P4VP) was obtained through hydrolysis of diblock copolymer of poly(tert‐butyl acrylate) (PtBA) and P4VP synthesized using atom transfer radical polymerization. Water‐soluble micelles with PAA core and P4VP corona were observed at low (acidic) pH, while micelles with P4VP core and PAA corona were formed at high (basic) pH. Two metalloporphyrins, zinc tetraphenylporphyrin (ZnTPP) and cobalt tetraphenylporphyrin (CoTPP), were used as model compounds to investigate the encapsulation of hydrophobic molecules by both types of micelles. UV–vis spectroscopic measurements indicate that micelles with P4VP core are able to entrap more ZnTPP and CoTPP as a result of the axial coordination between the transition metals and the pyridine groups. The study found that metalloporphyrins encapsulated by the micelles with PAA core could be released on pH increase, while those entrapped by the micelles with P4VP core could be released on pH decrease. This behavior originates from the two‐way pH change‐induced disruption of PAA‐b‐P4VP micelles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1734–1744, 2006     

Preparation and application of simetryn‐imprinted nanoparticles in triazine herbicide residue analysis

This work provides a simple and rapid method for synthesis uniform simetryn imprinted nanoparticles, which can be used to pretreat the tested samples before detecting. A series of computational approach were employed for design simetryn‐imprinted polymer. Based on the conclusion of theoretical calculation, the simetryn imprinted nanoparticles were synthesized using simetryn as template, methacrylic acid as monomer with different solvent volume and synthesis conditions. The obtained nanoparticles have small size, uniform distribution and high imprinted factor. Scatchard analysis and quantum chemical calculations were applied for evaluating the interaction of simetryn with methacrylic acid in the imprinting process. The selectivity and recognition ability of the simetryn imprinted nanoparticles for six triazine herbicides and two other type herbicides were investigated. The results show that the simetryn imprinted nanoparticles had high selectivity and binding capacity and could be used for the separation and enrichment of four triazine pesticide residues from actual samples. A method of molecularly imprinted matrix solid phase extraction ultra‐performance liquid chromatography tandem mass spectrometry was established for detecting four kinds of triazine herbicide residues in tobacco. The recovery rate of terbuthylazine, simetryn, atrazine, and prometryn in tobacco was 84.03–119.05%, and the relative standard deviation was 0.35–10.12%.     

Novel metal‐ion‐mediated,complex‐imprinted solid‐phase microextraction fiber for the selective recognition of thiabendazole in citrus and soil samples

A novel metal‐ion‐mediated complex‐imprinted‐polymer‐coated solid‐phase microextraction (SPME) fiber used to specifically recognize thiabendazole (TBZ) in citrus and soil samples was developed. The complex‐imprinted polymer was introduced as a novel SPME coating using a “complex template” constructed with Cu(II) ions and TBZ. The recognition and enrichment properties of the coating in water were significantly improved based on the metal ion coordination interaction rather than relying on hydrogen bonding interactions that are commonly applied for the molecularly imprinting technique. Several parameters controlling the extraction performance of the complex‐imprinted‐polymer‐coated fiber were investigated including extraction solvent, pH value, extraction time, metal ion species, etc. Furthermore, SPME coupled with HPLC was developed for detection of TBZ, and the methods resulted in good linearity in the range of 10.0–150.0 ng/mL with a detection limit of 2.4 ng/mL. The proposed method was applied to the analysis of TBZ in spiked soil, orange, and lemon with recoveries of 80.0–86.9% and RSDs of 2.0–8.1%. This research provides an example to prepare a desirable water‐compatible and specifically selective SPME coating to extract target molecules from aqueous samples by introducing metal ions as the mediator.     

On‐Line Selective Solid‐Phase Extraction of Copper with a Surface Ion Imprinted Silica Gel Sorbent

Copper(II)‐ion imprinted silica gel (Cu‐IISG) sorbent was synthesized by surface imprinting technique and was employed as a selective solid‐phase extraction material for on‐line preconcentration and separation, then coupled with atomic absorption spectrometry (AAS) determination of Cu(II). The higher selectivity coefficient of Cu‐IISG for Cu(II) in the presence of competitive ions such as Fe(III), Ni(II) and Zn(II) was above 411, which was 35 times of NISG. The static adsorption capacity and dynamic adsorption capacity were 41.11 mg g^?1 and 16.20 mg g^?1, respectively. The Cu‐IISG offered a fast kinetics for the adsorption and desorption of Cu(II), which can be used for on‐line preconcentration and detection. Two certified reference materials of GBW07301a sediment and GBW07401 soil were analyzed and the determined values were in a good agreement with the certified values. The developed method was also successfully applied to the determination of trace copper in tea leaf with satisfactory results (recovery between 96.3% and 102.3%).     

Novel Imprinted Polymer for the Preconcentration of Cadmium with Determination by Inductively Coupled Plasma Mass Spectrometry

A novel Cd(II)-imprinted polymer was prepared with chemical immobilization using N-methacryloyl-L-Histidine as a vinylated chelating agent for online solid-phase extraction of Cd(II) for determination by inductively coupled plasma mass spectrometry. The Cd(II)–monomer complex was synthesized and copolymerized through bulk polymerization method in the presence of ethyleneglycoldimethacrylate cross-linker. The resulting polymer was leached with 1.0?mol?L^?1 HNO₃ to generate the cavities in the polymer for Cd(II) ions. The experimental conditions, including load pH, solution flow rate, and eluent concentration for effective sorption of Cd(II), were optimized using a minicolumn of the imprinted polymer. A volume of 5.0?mL sample 5?µg?L^?1 Cd(II) solution at pH 6.5 was loaded on the column at 2.0?mL?min^?1 using a sequential injection system followed by elution with 1.0?mL of 0.75?mol?L^?1 HNO₃. The relative selectivity coefficients of the imprinted polymer for Cd(II) were 38.5, 3.5, 3.0, 2.5, and 6.0 in the presence of Cu(II), Ni(II), Zn(II), Co(II), and Pb(II), respectively. Computational calculations revealed that the selectivity of the imprinted polymer was mediated by the stability of Cd(II)–N-methacryloyl-L-Histidine complex which was more stable than commonly used monomers including 4-vinyl pyridine, methacrylic acid, and vinylimidazole. The detection limit and relative standard deviation were 0.004?µg?L^?1 and 3.2%, respectively. The method was validated by the analysis of seawater certified reference material (CASS-4) and successfully used for the determination of Cd(II) in coastal seawater and estuarine water.     

Hollow‐particle latexes: Preparation and properties

Hollow‐particle latexes were prepared according to the following stages: (1) the preparation of the methyl methacrylate–methacrylic acid (MAA)–ethylene glycol dimethacrylate copolymer ( I ) latex, (2) the preparation of a shell ( II ) based on polystyrene or styrene–acrylonitrile–divinyl benzene copolymer polymerized onto copolymer ( I ) particles, and (3) the neutralization of the core ( I ) carboxyl groups with a base (NH₄OH or NaOH) at temperatures close to the glass‐transition temperature of the polymer ( II ). The neutralization resulted in the expansion of the particles and formed water‐filled hollow particles. The microspheres had an overall diameter of 460–650 nm and a hollow diameter of 300–450 nm. Rheological studies and particle size measurements by transmission electron microscopy and dynamic light scattering of the copolymer ( I ) latex indicate that the maximum particle swelling occurred at an approximately equimolar MAA/base ratio. It was found that even without the neutralization of the MAA units, a small hollow formation in the latex particles occurred during stage 2 because one volume of the copolymer ( I ) retained about 8 volume parts of water. It was also discovered that the final hollow‐particle geometry after neutralization depends on the shell copolymer thickness and type as well as on the conditions during stage 3, that is, the time, temperature, base type, and concentration. The opacifying ability of the synthesized hollow particles was investigated in latex coatings. The opacifying ability values were generally in agreement with the hollow‐particle geometry. The only exception was related to the copolymer ( I )/copolymer ( II ) ratio. The maximum hollow volume was obtained at this value equal to 1/8, whereas the highest opacifying ability was observed at 1/10. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1435–1449, 2001     

Designing superhydrophobic surface based on fluoropolymer–silica nanocomposite via RAFT‐mediated polymerization‐induced self‐assembly

Superhydrophobic surfaces (SHS) find versatile applications as coatings due to their very high water‐repellency, self‐cleaning, and anti‐icing properties. This investigation describes the preparation of a SHS from surfactant‐free hybrid fluoropolymer latex. In this case, reversible addition‐fragmentation chain transfer (RAFT) polymerization was adopted to prepare a copolymer of 4‐vinyl pyridine (4VP) and vinyl triethoxysilane (VTES), where the pyridine units were quaternized to make the copolymer soluble in water. The copolymer was further used as a macro‐RAFT agent to polymerize 2,2,2‐trifluoroethyl methacrylate (TFEMA) in a surfactant‐free emulsion via polymerization‐induced self‐assembly (PISA). The macro‐RAFT agent contained a small amount of VTES as co‐monomer which was utilized to graft silica nanoparticles (SNPs) onto the P(TFEMA) spheres. The film prepared using the nanocomposite latex exhibited a nano‐structured surface as observed by SEM and AFM analyses. Surface modification of the film with fluorinated trichlorosilane produced an SHS with a water contact angle (WCA) of 151.5°. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 266–275     

Synthesis of a New Cu(II)-Ion Imprinted Polymer for Solid Phase Extraction and Preconcentration of Cu(II)

A new Cu(II)-ion imprinted polymer (IIP) has been synthesized by copolymerizing salicylic acid and formaldehyde as a monomer and crosslinker, respectively in the presence of Cu(II)-4-(2-pyridylazo) resorcinol complex. The imprinted Cu(II) ions were completely removed by leaching the IIP with 0.05 M EDTA. The maximum adsorption capacity for Cu(II) ions was 310 μg g^?1 at pH 6. The IIP was repeatedly used in adsorption–desorption experiments for seven times with recoveries ~95%. The relative selectivity factor (α _r) values of Cu(II)/Zn(II), Cu(II)/Cd(II), Cu(II)/Ni(II) and Cu(II)/Co(II) are 3.17, 2.90, 2.47 and 3.37, respectively. The detection limit corresponding to three times the standard deviation of the blank was found to be 3.0 μg L^?1. The developed IIP has also been tested for preconcentration and recovery of Cu(II) ions from water samples.     

Preparation of a multi‐hollow magnetic molecularly imprinted polymer for the selective enrichment of indolebutyric acid

A simple strategy was developed for the preparation of multi‐hollow magnetic molecularly imprinted polymers by incorporating 3‐indolebutyric acid and ferroferric oxide nanoparticles simultaneously into a poly(styrene‐co‐methacrylic acid) copolymer matrix. The as prepared absorbents were characterized using scanning electron microscopy, Fourier‐transform infrared spectroscopy and mercury porosimetry. The adsorption isotherms of indolebutyric acid revealed that there are two types of affinity binding sites in the absorbents. The apparent maximum binding capacity and dissociation constant were 17.88 mg/g and 158.7 μg/mL for high‐affinity binding sites and 9.310 mg/g and 35.04 μg/mL for low‐affinity binding sites, respectively. The results testified that multi‐hollow magnetic molecularly imprinted polymers possessed excellent recognition capacity and fast kinetic binding behavior to the objective molecules due to the high specific surface area as large as 511.3 m²/g. Recoveries of 75.5–86.8% were obtained for the indolebutyric acid spiked at three concentration levels in blank and pear samples.