We developed an efficient and mild method for the preparation of boronic acid-functionalized magnetic nanoparticles (MNPs), and the selective separation of fructose from a sample solution was demonstrated for the first time. A modified hydrothermal method was chosen to prepare the naked Fe3O4 MNPs, and then the Fe3O4@SiO2 MNPs were synthesized by a sol–gel reaction. After that, the thiol-coated Fe3O4 MNPs were synthesized by a sol–gel reaction with an organosilicon coupling agent. Finally, the thiol groups on the surface of the MNPs served as clickable sites to react with 4-vinylphenylboronic acid (VPBA) via a thiol–ene (TE) click reaction to obtain the final MNPs with a high density of boronic acid ligands immobilized on the surface. It is known that phenylboronic acid ligands on Fe3O4@SiO2@VPBA MNPs can form stable five- or six-membered cyclic esters with cis-diol-containing molecules. In this work, the click-Fe3O4 MNPs with a mean diameter of 195 nm exhibited high selectivity and binding capacity towards fructose. Also, the adsorption efficiency of fructose could reach ≈96% under optimum adsorption conditions. In addition, the adsorption efficiency of fructose was about six times higher than that of glucose in a fructose–glucose aqueous solution, suggesting that the resultant Fe3O4@SiO2@VPBA MNPs had higher affinity for fructose under the interference of competing glucose. Reusability is also an important factor of affinity adsorbents, and the adsorption capacity of Fe3O4@SiO2@VPBA MNPs was virtually unchanged after six cycles of reuse.

•A fluorescence probe for Hg2 + and Zn2 + ions was designed and synthesized.•The geometry optimizations were carried out using the Gaussian 09 program based on DFT.•The method exhibited high selectivity and sensitivity, wide range of linear response and low detection limit.•The fluorescence chemosensor can be used for imaging of metal ions in living cells.A fluorescence probe has been designed and synthesized, and applied with a combined theoretical and experimental study. Research suggests that the probe can be used to sense Zn2 + and Hg2 + through selective turn-on fluorescence responses in the aqueous HEPES buffer (0.05M, pH = 7.4). The limit of detection (LOD) were determined as 1.46 × 10− 7 M (Zn2 +) and 2.50 × 10− 7 M (Hg2 +). Moreover, based on DFT, the geometry optimizations of probe 1, [1-Hg2 +] complex and [1-Zn2 +] complex were carried out using the Gaussian 09 program, in which the B3LYP function was used. The electronic properties of free probe 1 and the metal complexes were studied based on the Natural Bond Orbital (NBO) analyses. The probe 1 has also been successfully applied to detection of Zn2 + and Hg2 + in living cells.Download high-res image (71KB)Download full-size image

•A novel type of multifunctional chemosensors to Al3+, Zn2+ and temperature was reported.•The chemosensor can distiguish Al3+ and Zn2+ in their mixed solution by controlling the response time.•The detection limit of Al3+ and Zn2+ ions at 40 °C can be decreased to ∼2.14 and ∼8.71 ppb, respectively.•The chemosensor showed a high stability and feasibility for analysis in biological samples.In this paper, a novel type of responsive double hydrophilic block copolymer (DHBC)-based multifunctional chemosensors to Al3+, Zn2+ and temperature was designed and prepared. The well-defined DHBCs with Al3+ and Zn2+-reactive thermosensitive block (copolymer fluorescence chemosensor), poly(ethylene oxide)-b-poly(N-isopropylacrylamide-co-SHMA)65(PEO113-b-P(NIPAM-co-SHMA)65, Mn = 13.2 kDa, Mw/Mn = 1.09), were synthetized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The novel well water-soluble copolymer fluorescence chemosensor could selectively recognize Al3+ (blue fluorescence) and Zn2+ (green fluorescence) by the difference of the fluorescence color. Moreover, this copolymer fluorescence chemosensor has the ability to selective recognition Al3+ or Zn2+ in their mixed solution by controlling the fluorescence response time. The detection limit of 0.1 g/L copolymer fluorescence chemosensor for the analysis of Al3+ and Zn2+ ions at 25 °C were calculated to be ∼5.23 and ∼11.99 ppb, respectively. PEO113-b-P(NIPAM-co-SHMA) can self-assemble into micelles with P(NIPAM-co-SHMA) block as core and well-solvated PEO block as coronas when heating to the lower critical solution temperature (LCST), and the detection limit of Al3+ and Zn2+ ions at 40 °C can be decreased to ∼2.14 and ∼8.71 ppb, respectively. Furthermore, the copolymer fluorescence chemosensor has been successfully applied to detect Al3+ and Zn2+ in biological samples.Download high-res image (155KB)Download full-size image

The cloud point (CP) values of aqueous solutions of the triblock copolymer L64 were determined in the absence and presence of five salting-out salts (K2SO4, Na2SO4, (NH4)2SO4, K2CO3, K2HPO4) at different concentrations. All the five salts could decrease the CP values and form aqueous two phase systems (ATPSs) with L64. A notable phase inversion phenomenon occurred with the increasing salt concentrations and the phase inversion points were found. The salt-rich phase transferred from the top phase to the bottom phase because of the change of density. Liquid–liquid equilibrium (LLE) data of these ATPSs were measured at 45 °C, respectively. The consistency of the tie-lines was verified by using the empirical equations from the Othmer-Tobias and Bancroft correlation. The effects on the cloudy behavior and phase separation depended on the salting-out ability. The results showed that the salting-out ability of the cations followed the order: Na+ > K+ > NH4+NH4+; the anions followed the order: HPO42−HPO42− > SO42−SO42− > CO32−CO32−. It could be concluded that using the Gibbs free energy of hydration of the ions (ΔGHyd) to estimate salting-out ability was not suitable for all of the ATPSs.

As a novel and green pretreatment technique to trace samples, polyoxyethylene cetyl ether (POELE20)–(NH4)2SO4 aqueous two-phase extraction system was coupled with high-performance liquid chromatography to analyse synchronously chloramphenicol (CAP), thiamphenicol (TAP) and florfenicol (FF) in chicken and pork samples. It was found that the extraction efficiency (E%) and enrichment factor (F) of the three antibiotics were influenced by the types of salts, the concentration of salt, the concentration of POELE20, system temperature and pH. The final optimal condition was as following: the phase-forming salt is (NH4)2SO4, the concentration of (NH4)2SO4 is 0.141 g mL−1, the concentration of POELE20 is 0.03 g mL−1, the temperature is 298.15 K, and the system pH is 4.5. This POELE20–(NH4)2SO4 ATPS was applied to separate and enrich three antibiotics in real sample under the optimal conditions, and it was found that the recovery was 97.20–102.00 % with a RSD of 0.61–4.85 %. The limit of detection for CAP, TAP and FF were 0.10, 0.50 and 0.50 μg kg−1, and the limit of quantitation for CAP, TAP and FF was 0.15, 1.50 and 1.50 μg kg−1. Seven times the experiments were used to verify the repeatability and veracity of this method, and the RSD for the intra-day and inter-day were 1.13–3.22 and 1.74–4.72 %.

•Discrimination of 13 catechols with a smallest-scale 2×2 colorimetric sensor array.•The coupling of a colorimetric sensor array/smartphone ensemble to a remote server.•Rapid on-site analysis and real-time generation of results with only a smartphone.•Practical application of a colorimetric sensor array in to real samples.The search of a practical method to analyze cis-diol-containing compounds outside laboratory settings remains a substantial scientific challenge. Herein, a smartphone-based colorimetric reader was coupled with a remote server for rapid on-site analysis of catechols. A smallest-scale 2×2 colorimetric sensor array composed of pH indicators and phenylboronic acid was configured. The array was able to distinguish 13 catechols at 6 serial concentrations, through simultaneous treatment via principal component analysis, hierarchical cluster analysis, and linear discriminant analysis. After both the discriminatory power of the array and the prediction ability of the partial least squares quantitative models were proved to be predominant, the smartphone was coupled to the remote server. All the ΔRGB data were uploaded to the remote server wherein linear discriminant analysis and partial least squares processing modules were established to provide qualitative discrimination and quantitative calculation, respectively, of the analytes in real time. The applicability of this novel method to a real-life scenario was confirmed by the on-site analysis of various catechols from a water sample of the Yangtze River; the feedback result in the smartphone showed the method was able to identify the catechols with 100% accuracy and predict the concentrations to within 0.706–2.240 standard deviation.

Binodal data for the 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim]BF4) + salt (MgCl2/Na2WO4) + H2O systems were experimentally determined at T = (288.15, 298.15, and 308.15) K, respectively. The binodal data were successfully correlated by an empirical equation with four parameters. The liquid–liquid equilibrium data were given and satisfactorily correlated by the Othmer–Tobias and Bancroft equations, as well as a two-parameter equation. Additionally, the Chen-NRTL model, the Pitzer-Debye–Hückel equation, and the Flory–Huggins equation were used to determine and correlate the liquid–liquid equilibrium data for the studied systems, and good agreement was obtained with these thermodynamic models. The influences of the two salts and temperature on the phase equilibrium were investigated. The phase-separation ability of MgCl2 is stronger than that of Na2WO4. As the temperature of the systems decreases, the two-phase region shows an expansion trend.

A new simple cyclic non-ligand dual-cloud point extraction (NL-DCPE) pretreatment method through pH regulation coupled with flame atomic absorption spectrometry (FAAS) for the analysis of trace cadmium(II) was developed. In NL-DCPE, the cloud point process was carried out twice. First, Cd(II) was extracted into the thermosensitive triblock copolymer L31-rich phase in the form of Cd(OH)2 at pH 13.33, leaving the hydrophilic impurities behind in the aqueous phase. Second, the hydroxide dissociated at pH 3.05 and Cd(II) was back-extracted into the aqueous phase in the form of Cd2+, thereby discarding the hydrophobic impurities in the L31-rich phase. The L31-rich phase was recycled, and the extraction efficiency could reach up to 90%. Under the optimum conditions, the preconcentration of a 10 mL sample solution could achieve an enrichment factor of 29 and an extraction efficiency of 96.3%. The relative standard deviation (RSD) for six replicate determinations was 4.5%. The method was applied to the determination of trace Cd(II) in food and environmental samples, and the range of recoveries were 90–102.5%. NL-DCPE successfully achieved the selective separation of the analytes and avoided the interference of the surfactant on the instrument analysis. This method had distinct advantages of simplicity, efficiency, economy and environmental protection, and also has great potential for the preconcentration and separation of other metal ions.

A novel three-phase ionic liquid hollow fiber liquid phase microextraction (IL-HF-LPME) system was used for the selective extraction and preconcentration of Pb(II) from medicinal plants. Green solvent ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF6) containing dicyclohexyl-18-crown-6 (DCH18C6) was used as membrane phase immobilized in the hollow fiber pores. Ethylene diamine tetraacetic acid was used as stripping agent that can form water-soluble complex with Pb(II) in the lumen of the hollow fiber. After extraction, the acceptor solution was directly injected into a graphite furnace atomic absorption spectrometer for analysis. A Box–Behnken design was used to study the influence of DCH18C6 concentration, extraction time and pH on the extraction efficiency. Under the optimized conditions, an enrichment factor of 199 and a limit of detection of 0.008 ng mL−1 were obtained. The calibration curve was linear in the range of 0.05–0.5 ng mL−1 (R = 0.999). Moreover, the obtained results show that DCH18C6 can selectively and efficiently transport Pb(II) from the aqueous phase containing different concentrations of heavy metal ions (Cd2+, Co2+, Cu2+, Ni2+, Fe2+, Zn2+). The proposed method was successfully applied to determination of Pb(II) in medicinal plants with satisfactory recoveries in the range of 94–102%.

The cloud point of thermosensitive triblock polymer L61, poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO), was determined in the presence of various electrolytes (K2HPO4, (NH4)3C6H5O7, and K3C6H5O7). The cloud point of L61 was lowered by the addition of electrolytes, and the cloud point of L61 decreased linearly with increasing electrolyte concentration. The efficacy of electrolytes on reducing cloud point followed the order: K3C6H5O7 > (NH4)3C6H5O7 > K2HPO4. With the increase in salt concentration, aqueous two-phase systems exhibited a phase inversion. In addition, increasing the temperature reduced the concentration of salt needed that could promote phase inversion. The phase diagrams and liquid–liquid equilibrium data of the L61-K2HPO4/(NH4)3C6H5O7/K3C6H5O7 aqueous two-phase systems (before the phase inversion but also after phase inversion) were determined at T = (25, 30, and 35) °C. Phase diagrams of aqueous two-phase systems were fitted to a four-parameter empirical nonlinear expression. Moreover, the slopes of the tie-lines and the area of two-phase region in the diagram have a tendency to rise with increasing temperature. The capacity of different salts to induce aqueous two-phase system formation was the same order as the ability of salts to reduce the cloud point.

Phase diagram and liquid–liquid equilibrium (LLE) data for the 1-alkyl-3-methylimidazolium tetrafluoroborate ([Cnmim]BF4 (n = 2,3,4)) + (NH4)2SO4 + H2O aqueous two-phase systems (ATPSs) were determined experimentally at T = (288.15, 298.15, and 313.15) K. The binodal curves were fitted by a four-parameter equation. On the basis of the empirical equation of the binodal curve with the highest accuracy and lever rule, the LLE data were calculated by MATLAB. The tie-lines were correlated by the Othmer–Tobias and Bancraft equations. In particular, the temperature dependence on the binodal curves and tie-lines was discussed, it was found that an decreasing in temperature caused the expansion of two-phase region. Furthermore, the effect of the ionic liquid structure on the phase equilibrium of ATPSs has been studied, the results showed that the ability of phase separation of the IL-based ATPSs follows the order [C4mim]BF4 > [C3mim]BF4 > [C2mim]BF4.

Ionic liquid-based aqueous two-phase systems offer an attractive alternative to volatile organic solvents in liquid–liquid extraction. In this work, the phase diagrams of the 1-alkyl-3-methyl imidazolium tetrafluoroborate ([C2mim]BF4/[C4mim]BF4) + ZnSO4/MgSO4/Li2SO4 + H2O ATPSs were determined at 298.15 K. Three empirical equations were used to correlate the binodal data and the optimum equation was selected. The effective excluded volume (EEV) values obtained from the binodal model for these systems were determined. The EEV and the binodal curves plotted in molality both indicate that the salting-out abilities of the three salts follow the order: ZnSO4 > MgSO4 > Li2SO4, while the phase-separation abilities of the investigated ILs are in the order of [C4mim]BF4 > [C2mim]BF4. Finally, the liquid–liquid equilibrium data were successfully correlated by the Othmer-Tobias and Bancroft equations, meanwhile the slope of tie line increased with an increase in cation alkyl chain length.Highlights► We discuss the liquid–liquid equilibrium of imidazolium ILs + sulfate salts ATPSs. ► The optimum equation was selected to correlate the binodal data. ► We correlate the tie-lines using some appropriate equations. ► The salting-out ability is ZnSO4 > MgSO4 > Li2SO4. ► The phase-separation abilities are in the order of [C4mim]BF4 > [C2mim]BF4.

•Simultaneous ATPF of sodium chlorophyllin and removal of sugars in one system.•High removal percentage of sugars by ATPF.•Demonstration of surface-activity of sodium chlorophyllin by experiment.An ethanol–tripotassium phosphate aqueous two-phase flotation (ATPF) system was first time studied for the separation of sodium chlorophyllin and sugars. The single factors influencing the recovery of sodium chlorophyllin in the top phase and removal of sugars in the bottom phase were investigated and optimized by response surface methodology (RSM). The maximum recovery percentage (88.28%) of sodium chlorophyllin were obtained at 0.55 g/mL of tripotassium phosphate, 25 mL/min of nitrogen flow rate, 26 min of flotation time and 5 mL of ethanol, meanwhile, the removal percentage of sugars reached 95.84%. Compared with aqueous two-phase extraction (ATPE), ATPF showed advantages of low consumption of organic solvent, high enrichment factors, and high separation effect. Sodium chlorophyllin were demonstrated theoretically and experimentally to have surfactivity. Finally, the scale-up experiments were conducted to further prepare sodium copper chlorophyllin, and the absorbance ratio (A406.00 nm/A631.00 nm) was 3.49. This method may blaze the trail for mass production of sodium copper chlorophyllin in industry.Download full-size image