Preparation of amino acid chiral ionic liquid and visual chiral recognition of glutamine and phenylalanine enantiomers.

In this paper, the amino acid chiral ionic liquid (AACIL) was prepared with L-phenylalanine and imidazole. It was characterized by CD, FT-IR, 1H NMR, and 13C NMR spectrum. The chiral recognition sensor was constructed with AACIL and Cu(II), which exhibited different chiral visual responses (solubility or color difference) to the enantiomers of glutamine (Gln) and phenylalanine (Phe). The effects of solvent, pH, time, temperature, metal ions, and other amino acids on visual chiral recognition were optimized. The minimum concentrations of Gln and Phe for visual chiral recognition were 0.20 mg/ml and 0.28 mg/ml, respectively. The mechanism of chiral recognition was investigated by FT-IR, TEM, SEM, TG, XPS, and CD. The location of the host-guest inclusion or molecular placement has been conformationally searched based on Gaussian 09 software.

Synthesis of CoFe2O4@SiO2-NH2 and its application in adsorption of trace lead.

In this work, an amine functionalized CoFe2O4 magnetic nanocomposite material CoFe2O4@SiO2-NH2 was prepared successfully by modifying coated-CoFe2O4@SiO2 magnetic nanoparticles with 3-aminopropyltriethoxysilane (APTES) and became an efficient adsorbent for the separation and analysis of trace lead in water. The CoFe2O4@SiO2-NH2 magnetic nanoparticles were characterized using SEM, TEM, XRD, FTIR, VSM and BET techniques. Then, the adsorption mechanism was preliminarily investigated through ZETA, XPS, and adsorption kinetic experiments. The adsorption process was fitted by pseudo-second-order kinetics and a Langmuir isotherm model. The main adsorption mechanism of CoFe2O4@SiO2-NH2 towards lead ions was the chelation between the amino groups of CoFe2O4@SiO2-NH2 and lead cations, as well as the strong Coulomb interaction between the electron donor atoms O and N in the surface of CoFe2O4@SiO2-NH2 and lead cations. The adsorption capacity is 74.5 mg g-1 and the adsorbent can be reused 5 times. Hence, this prepared CoFe2O4@SiO2-NH2 could find potential applications for the removal of trace metal ions in surface water.

Preparation of Chiral Carbon Quantum Dots and its Application.

Chiral carbon quantum dots (cCQDs) , as a new type of carbon nano-functional material with tunable emission wavelength, superior photostability, low toxicity, biocompatibility and chirality, are playing an increasingly important role in the fields of chemistry, biology and medicine. This paper reviews the preparation methods (one-step and two-step), optical properties (UV, fluorescence, chirality) and applications in chiral catalysis, chiral recognition, targeted imaging as well as other fields, while lists some of the issues and challenges in the research of chiral carbon quantum dots. Finally, due to its good fluorescence and other properties, it is expected that chiral carbon quantum dots will have broad commercial prospects in future applications.

One-step hydrothermal preparation of chiral carbon quantum dots and enantioselective sensing of glutamine enantiomeric isomers.

A novel method for chiral identification of glutamine enantiomers based on chiral carbon quantum dots (cCQDs) fluorescent probes. cCQDs were prepared using a one-step hydrothermal method with L-tryptophan as the carbon source and chiral source, producing spherical nanoparticles exhibiting a blue colour luminescence. The fluorescence intensity (F) of cCQDs was enhanced or quenched following the addition of chiral enantiomeric glutamine (L/D-Gln), and therefore cCQDs, as a fluorescence probe, could be used for enantioselective sensing of the L/D-Gln. The fluorescence enhancement value (∆FE ) exhibited good linearity with L-Gln concentration in the range 0.23-10.00 mM, and the limit of detection was 0.14 mM. The fluorescence quenching value (∆FQ ) showed a good linear relationship with D-Gln concentration in the range 0.29-10.00 mM, and the detection limit was 0.18 mM. The mechanism of fluorescence enhancement/quenching was explored by molecular modelling and the type of quenching. The method was applied to the determination of L-Gln content in real samples, and the recovery rate was satisfactory. This study provided a novel approach for the synthesis of cCQDs and the recognition of amino acid enantiomers.

Pyridine ionic liquid functionalized bimetallic MOF solid-phase extraction coupled with high performance liquid chromatography for separation/analysis sunset yellow.

An effective method based on the pyridine ionic liquid functionalized bimetallic MOF solid-phase extractant (Cu/Co-MOF@[PrPy][Br]) coupled with high performance liquid chromatography (HPLC) for the separation/analysis sunset yellow was established. Cu/Co-MOF@[PrPy][Br] was characterized by FTIR, XRD, SEM and TEM. Several important factors, such as pH, amount of extractant, extract time, and types of eluents were investigated in detail. Under the optimal conditions, linear range of the method was 0.05-40.00 µg mL-1, the detection limit was 0.02 µg mL-1, and the linear correlation was good (R 2 = 0.9992). The analysis of sunset yellow in soda, effervescent tablet and jelly proved that the method was simple and effective.

Ni-MOF Functionalized Carbon Dots with Fluorescence and Adsorption Performance for Rapid Detection of Fe (III) and Ascorbic Acid.

In this work, an "on-off-on" fluorescent probe based on Ni-MOF functionalized Nitrogen-doped carbon quantum dots (Ni-MOF-NCDs) was developed. Ni-MOF-NCDs was characterized by FT-IR, TEM, SEM, and XPS. The presence of Fe (III) will reduce the fluorescence intensity of Ni-MOF-NCDs and "turn off" the fluorescence signal at emission peak of 390 nm, while the signal can be "turn on" after the addition of ascorbic acid (AA). The Ni-MOF-NCDs was established as an "on-off-on" fluorescent probe for the detection of Fe (III) and AA with the linear ranges of 0.029-8.0 µg/mL and 0.263-18.0 µg/mL, respectively. The method has been successfully applied to the detection of water samples and foods with satisfactory recovery. The experimental results showed that Ni-MOF-NCDs not only had the fluorescence properties of NCDs, but also had the adsorption performance of Ni-MOF.

Imidazole ionic liquid functionalized ZIF-67 molecularly imprinted solid-phase extraction coupled with high performance liquid chromatography for analysis of bisphenol A.

An effective method based on an imidazole ionic liquid functionalized ZIF-67 molecularly imprinted solid-phase extractant (ZIF-67@[Bmim][Br]@MIP) coupled with high performance liquid chromatography (HPLC) for the separation/analysis of bisphenol A (BPA) was established. ZIF-67@[Bmim][Br]@MIP was characterized by FTIR, XRD, SEM, TEM and BET. Several important factors, such as pH, amount of extractant, extraction time, and types of eluents were investigated in detail. Under the optimal conditions, the linear range of the method was 0.01-20.00 µg mL-1, the detection limit was 5.0 ng mL-1, and the linear correlation was good (R2 = 0.9994). The detection of BPA in mineral water bottles, milk cartons and milk tea cups proved that the method was simple and effective, and could be used to separate and analyze BPA in real samples.

On-line separation/analysis of Rhodamine B dye based on a solid-phase extraction high performance liquid chromatography self-designed device.

A special self-designed device based on poly-1-vinyl-3-pentylimidazole hexafluorophosphate (PILs-C5) solid-phase extraction and high performance liquid chromatography (HPLC) is proposed as a novel method for the on-line separation and analysis of Rhodamine B (RhB) dye. Single factor experiment design and orthogonal experiment design were used to optimize the experimental parameters, such as pH, the amount of PILs-C5, sample volume, flow rate, eluent type, eluent concentration, eluent volume, and the flow rate of eluent. Under the optimized conditions, the linear range was 0.02-2.4 µg mL-1, with the correlation coefficients (R 2) of 0.997. The limit of detection (LOD) and limit of quantification (LOQ) were 0.004 µg mL-1 and 0.02 µg mL-1, respectively. The extraction capacity was 6.22 mg g-1, and enrichment ratio was 15. The extraction mechanism and the post-treatment method of PILs-C5 were also studied. This method was applied to analyze RhB in a wide variety of real samples with satisfactory results.

Choline Proline Ionic Liquid-Functionalized Fe3O4@SiO2 Nanoparticle Magnetic Solid Phase Extraction Coupled with High-Performance Liquid Chromatography for Analysis of Allura Red in Lipstick Sample.

A separation/analysis of allura red based on magnetic solid-phase extraction-high-performance liquid chromatography was developed. The extractant was prepared by functionalizing choline proline ionic liquid on Fe3O4@SiO2(Fe3O4@SiO2@[Ch][Pro]). Infl uences of experimental variables including extraction condition (material amount, pH, time, temperature, ionic strength, and sample volume) and elution conditions (eluent selection, amount, time) were evaluated. Under the optimal conditions, good linear calibration curves were obtained in the range of 0.02-5.0 µg/mL, and limits of detection was 9.0 ng/mL. The proposed method was successfully applied for the determination of allura red in lipstick sample.

A facile green and one-pot synthesis of grape seed-derived carbon quantum dots as a fluorescence probe for Cu(ii) and ascorbic acid.

In this study, an on-off-on fluorescence probe for the detection of trace Cu(ii) and ascorbic acid (AA) based on biomass-derived sulfur and nitrogen double heteroatom-doped carbon dots (N,S-CDs) was designed. For the first time, the probe (N,S-CDs) was prepared from grape seeds and thiourea as the precursor. Cu(ii) was added to the carbon point solution, the fluorescence intensity (FL) of N,S-CDs was strongly quenched (switch OFF) and the fluorescence probe turned to "ON" (switch ON) with the addition of AA. Under the optimal conditions, the as-synthesized N,S-CDs had a good detection performance for Cu(ii) and AA assay with the linearity ranges from 150-500 µg mL-1 and 0.1-400 µg mL-1, and the LODs were 0.048 mg L-1 and 0.036 mg L-1, respectively. The as-prepared N,S-CDs exhibited a low cytotoxicity and a good biocompatibility, which show their potential for application in the biological imaging of living cells.

Green choline amino acid ionic liquids aqueous two-phase extraction coupled with synchronous fluorescence spectroscopy for analysis naphthalene and pyrene in water samples.

A novel aqueous two-phase extraction method has been established for the determination of polycyclic aromatic hydrocarbons in water sample. This method was based on the extraction of naphthalene and pyrene from water by means of choline amino acid ionic liquids aqueous two-phase system and their determination by synchronous fluorescence spectroscopy. In synchronous fluorescence spectroscopy, the fluorescence peaks of naphthalene and pyrene were completely separated to meet the requirement of simultaneous determination. For this method, good linear calibration curves of naphthalene and pyrene were obtained in the range of 0.50-10.0, 0.05-5.0 µg mL-1, respectively, and limits of detection were 0.211, 0.012 µg mL-1, respectively. The proposed method was successfully applied for the simultaneous determination of naphthalene and pyrene in water samples, which was considered as an excellent green analysis according Analytical Eco-Scale.

Synthesis of Poly-Amino Acid Ionic Liquid Up-Conversion Fluorescent Probe and its Application in Fe(II)/Fe(III) Speciation Analysis.

The poly amino acid ionic liquid (poly-1-vinyl-3-butylimidazolium glutamate acid, p-1-VbmGlu), with a stable up-conversion fluorescence(UCF) probe, was firstly prepared and the synthesis conditions were optimized. The UCF were found to be specifically quenched by Fe(III), but not respond to Fe(II). In H2O2 medium, Fe(II) posed strong quenching effect on the UFC owing to Fe(III) produced by redox between H2O2.and Fe(II). Therefore p-1-VbmGlu was employed as a UFC for Fe(II)/Fe(III) speciation analysis under the control of H2O2. The detection limits of Fe(II)/Fe(III) were 6.16 ng/mL and 4.48 ng/mL, with relative standard deviations of 1.1% and 2.0%, respectively. This method was successfully utilized in the analysis of Fe(II)/Fe(III) in multiple real samples.

Magnetic graphene oxide-ultrathin nickel-organic framework composite for the extraction and determination of epoxiconazole in food samples.

In this work, a magnetic graphene oxide-ultrathin metal-organic framework composite (Fe3O4@SiO2-GO-Ni-MOF) was synthesized for the first time. Employing Fe3O4@SiO2-GO-Ni-MOF composite as extractant, a novel method for the separation and analysis of the pesticide epoxiconazole was established with the assistance of high performance liquid chromatography (HPLC). The adsorption mechanisms were studied including by adsorption kinetics, thermodynamic parameters and adsorption isotherms. The experimental results showed that this method was convenient, operable, effective and practical for the extraction and determination of epoxiconazole in real samples.

A novel fluorescence "turn off-on" sensor based on N-doped graphene quantum dots in amino acid ionic liquid medium and its application.

The spectrum behavior of N-doped graphene quantum dots (N-GQD) in 1-hexyl-3-methylimidazolium tryptophan ionic liquid (TryIL) was studied. It was showed that TryIL could self-aggregate into water/oil micellar in aqueous solution and N-GQD was assembled on hydrophilic part of TryIL micelle to construct a novel fluorescence "turn on-off" probe (N-GQD-TryIL). the fluorescence intensity was quenched through the formation of N-GQD-TryIL-Cu(II) complex due to the strong binding ability between Cu2+ and N-GQD-TryIL. In the following fluorescence "turn-on" step, the chiral ligand exchange between levodopa (LD) and Cu(II)-N-GQD-TryIL to partly recovery the fluorescence intensity. Corresponding influencing factors and mechanisms in fluorescence "turn-off" and "turn-on" process were discussed. Thus, a sensitive and selective fluorescence "turn off" and "turn on" platform for assay Cu(II) and LD was designed. Under the optimal conditions, Cu(II) and LD exhibited good linear relationship in the range of 0.051-16.00 µg/mL and 0.55-5.00 µg/mL. The LOD of them was 0.017 µg/mL and 0.16 µg/mL respectively. This method was successfully applied to the determination of Cu(II) and LD in real samples. Moreover, N-GQD-TryIL performed application prospects in bio-imaging due to protein affinity of the hydrophilic part.

Synthesis of uniform Ag nanosponges and its SERS application.

With the aid of amino acid, various Ag nanostructures were successfully synthesized via the reaction between silver nitrate and hydrazine hydrate at room temperature. The as-prepared products were characterized by X-ray diffraction and scanning electron microscopy. It was found that the morphology of the as-prepared Ag products depended on the sorts of amino acid and solvents. The uniform Ag nanosponges could be obtained in glycol with aid of glycine. Using rhodamine 6G (R6G) as probe, the surface-enhanced Raman scattering (SERS) performance was also investigated, which showed that the uniform Ag nanosponges exhibited an intensive and enhanced Raman scattering. Pazufloxacin mesilate (PM) were detected conveniently using these uniform nanosponges as SERS substrates. The present work might afford some guidance for the rationally controllable synthesis of other metal nanomaterials.

Speciation of inorganic arsenic(III) and arsenic(V) by a facile dual-cloud point extraction coupled with inductively plasma-optical emission spectrometry.

A simple and efficient method using dual-cloud point extraction (dual-CPE) coupled with inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the speciation of inorganic arsenic [As(III) and As(V)]. In first step of dual-CPE, As(III) formed a hydrophobic complex with ammonium pyrrolidine dithiocarbamate (As-APDC), and was subsequently entrapped by the Triton X-114 surfactant-rich phase at pH 5.0, whereas As(V) remained in the bulk supernatant. The surfactant-rich phase containing the As(III)-APDC complex was treated with a 2.0molL-1 of nitric acid, and As(III) was back extracted into the aqueous phase at the second cloud point extraction stage before ICP-OES detection. The As(V) concentration was calculated by subtracting the concentration of As(III) from the total inorganic arsenic concentration after reducing As(V) to As(III) by thiourea. Different factors affecting the extraction of As(III) were investigated in detail. Under the optimum conditions, the detection limit for As(III) was 0.72ngmL-1 along with the relative standard deviation of 3.5% (C = 10.0ngmL-1, n = 5). The calibration curve was linear in the range of 2.0-50.0ngmL-1. This method was validated against the certified reference material (GSBZ 50004-88), and applied for the speciation of inorganic As(III) and As(V) in the spiked snow water sample.

Simultaneous determination of Magnolol and Honokiol by amino acid ionic liquid synchronous fluorescence spectrometry.

A novel method based on amino acid ionic liquids (AAILs) as an additive synchronous fluorescence spectrometry is proposed for simultaneous determination of magnolol (MN) and honokiol (HN) in traditional Chinese medicine Houpu. The overlapping fluorescence spectrum of MN and HN could be completely separated in the AAILs medium. Experiment parameters (the type and concentration of AAILs, pH values and temperature) were discussed. The detection limits of MN and HN reached 1.46ng/mL, 0.92ng/mL and the recovery rates ranged from 98.6%-100.7%, 99.7%-100.6%, respectively. This methods was successfully employed for simultaneously determination of MN and HN in real samples. No significant differences could be found in the results of this method and the pharmacopoeia of People's Republic of China 2015 (Ch.P.2015). The experiment mechanisms were discussed by the Gaussian simulation and fluorescence quantum yield.

Use of Ionic liquids as additives in ion exchange chromatography for the analysis of cations.

The behavior of acids (citric acid, nitric acid, oxalic acid, tartaric acid) as a mobile phase and imidazolium ionic liquids (the bromides, tetrafluoroborates and hexafluorophosphates of 1-ethyl, 1-butyl, and 1-hexyl-3-methylimidazolium) as additives in ion exchange chromatography for cations (Na+ , K+ , Mg2+ , Ca2+ ) separation were studied. The results showed that nitric acid and 1-hexyl-3-methyl-imidazolium hexafluorophosphate offered the most interesting features in the separation of cations, such as lower retention time and better resolution. The selected optimal conditions were achieved by adding 0.10 mM 1-hexyl-3-methyl-imidazolium hexafluorophosphate in 4.0 mM HNO3 mobile phase for the separation of four cations with the flow rate of 0.9 mL/min at room temperature (25°C). The linear regression equations of Na+ , K+ , Mg2+ , Ca2+ were S = 4.4763c + 0.0209, S = 3.8903c - 0.0087, S = 6.3974c - 0.0173, and S = 7.601c - 0.0339 and the limits of detection of Na+ , K+ , Mg2+ , Ca2+ were 0.296, 4.98, 0.0970, and 1.22 µg/L, respectively. In this work, four cations in samples were successfully detected.

Speciation analysis of Mn(II)/Mn(VII) using Fe3O4@ionic liquids-ß-cyclodextrin polymer magnetic solid phase extraction coupled with ICP-OES.

Ionic liquids-ß-cyclodextrin polymer (ILs-ß-CDCP) was attached on Fe3O4 nanoparticles to prepare magnetic solid phase extraction agent (Fe3O4@ILs-ß-CDCP). The properties and morphology of Fe3O4@ILs-ß-CDCP were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction(XRD), size distribution and magnetic analysis. A new method of magnetic solid phase extraction (MSPE) coupled to ICP-OES for the speciation of Mn(II)/Mn(VII) in water samples was established. The results showed that Mn(VII) and total manganese [Mn(II)+Mn(VII)] were quantitatively extracted after adjusting aqueous sample solution to pH 6.0 and 10.0, respectively. Mn(II) was calculated by subtraction of Mn(VII) from total manganese. Fe3O4@ILs-ß-CDCP showed a higher adsorption capacity toward Mn(II) and Mn(VII). Several factors, such as the pH value, extraction temperature and sample volume, were optimized to achieve the best extraction efficiency. Moreover, the adsorption ability of Fe3O4@ILs-ß-CDCP would not be significantly lower after reusing of 10 times. The accuracy of the developed method was confirmed by analyzing certified reference materials (GSB 07-1189-2000), and by spiking spring water, city water and lake water samples.

[Fe3O4-ß-Cyclodextrin Polymer Nano Composites Solid-Phase Extraction-UV-Vis Spectrophotometry for Separation Analysis Malachite Green].

In this paper, carboxymethyl-hydroxypropyl-ß-cyclodextrin polymer modified magnetic particles Fe3O4 (CM-HP-ß-CD- CP-MNPs) were prepared and applied to magnetic solid phase extraction of malachite green combined with UV-Visible spectrom- etry detection. The synthesized magnetic particles were characterized by element analysis, Fourier transform infrared spectra and transmission electron microscopy. Several variables affecting the extraction and desorption of malachite green such as pH, the amount of adsorbent, the type and volume of eluent, extraction and desorption time, and temperature were investigated. Under the optimum conditions, malachite green could be adsorbed by CM-HP-ß-CDCP-MNPs (RE% = 92), and elution by C2H5OH (EE% = 90). the preconcentration factor of the proposed method was approximately 7.5, the CM-HP-ß-CDCP-MNPs could be used repeatedly for 5 times and offered better recovery. The linear range and detection limit (DL) were found to be 0.08~8.00 µg · mL⁻¹ and 5.6 ng · mL⁻¹ respectively. This technique had been successfully applied to the determination of malachite green in real samples. The inclusion interaction of CM-HP--CDCP-MNPs with malachite green was studied through FTIR.