Vortex-Assisted Liquid–Liquid Microextraction (VALLME): Applications

Recently, a new and fast equilibrium-based solvent microextraction technique termed vortex-assisted liquid–liquid microextraction was developed. In this technique, the dispersion of the extraction solvent is enhanced by vortex mixing. The aim of the present review is to discuss the applications of vortex agitation in solvent-microextraction procedures.     

Identification Markers of Adulteration in Korean Red Ginseng (Panax Ginseng) Products Using High-Performance Liquid Chromatography (HPLC) and Liquid Chromatography–Mass Spectrometry (LC-MS)

The commercial products of Panax ginseng have increasing market demand and high prices due to the pharmacological activities. To obtain high profits, P. ginseng may be adulterated with lower priced morphologically similar species such as Platycodon grandiflorum, Codonopsis lanceolata, and Pueraria lobata. This study was designed to validate accurate methods for the analysis of adulteration in P. ginseng products. High-performance liquid chromatography (HPLC) and ultraperformance liquid chromatography–diode array detector–electrospray ionization–ion trap–time of flight–mass spectrometry (UPLC–DAD–ESI-IT-TOF-MS) were validated to analyze the raw plant materials, self-prepared formulations, and commercial products of P. ginseng, C. lanceolata, P. grandiflorum, and P. lobata. The developed analytical methods were confirmed by quality assurance parameters such as linearity, sensitivity, precision, and accuracy. Lobetyolin and ononin were identified as marker compounds by HPLC and confirmed by accurate mass measurement with ESI-IT-TOF-MS. HPLC analysis of self-prepared formulations indicated that by increasing the ratio of C. lanceolata, P. grandiflorum, and P. lobata in P. ginseng extracts, the peak area is increased at the same retention time. The limits of detection and quantification for lobetyolin and ononin were 0.098 and 0.171, and 0.108 and 0.726?mg/kg, respectively. Furthermore, the intraday precision (<1.0%) measurements confirmed that the developed analytical methods fulfill the required criteria for characterization of these products. The results demonstrated that the developed liquid chromatographic and mass spectrometric methods accurately characterized adulteration in P. ginseng commercial products.     

Determination of Mycotoxins Using Hollow Fiber Dispersive Liquid–Liquid–Microextraction (HF-DLLME) Prior to High-Performance Liquid Chromatography – Tandem Mass Spectrometry (HPLC - MS/MS)

A modified hollow-fiber-supported dispersive liquid-liquid microextraction (HF-DLLME) method was developed for the determination of aflatoxins and ochratoxin A in food samples. The various parameters affecting the efficiency of extraction, such as pH, salt addition, extraction time, stirring rate, desorption time, type and volume of extractant and disperser solvents were carefully studied and optimized using two step strategies. The linearity of the evaluated results was 0.1 to 30?μg L^?1 for aflatoxins and 0.1 to 20?μg L^?1 for ochratoxin A, with regression coefficients (R²) exceeding 0.9990. The precision was satisfactory with relative standard deviation values less than 11%. The method accuracy was within the recommended range from 70% to 120% and analyte accuracy between 83% and 101%. The limits of detection and quantification were in the range from 0.04 to 0.06?μg L^?1 and 0.08 to 0.13?μg L^?1, respectively, for multi-aflatoxins, and 0.02 to 0.04?µg L^?1 and 0.08 to 0.10?µg L^?1, respectively, for ochratoxin A. The developed method was successfully applied for the determination of mycotoxins in food samples.     

Liquid crystalline phase transitions in hexakis(4-(4′-heptyloxy)biphenoxy)cyclotriphosphazene

Abstract

Hexakis(4-(4′-heptyloxy)biphenoxy)cyclotriphosphazene (HHCP) was synthesized from hexachlorocyclotriphosphazene and 4-heptyloxy-4′-hydroxybiphenyl. The mesogenicity of HHCP was studied by DSC, FTIR spectroscopy and polarizing microscopy. Enantiotropic smectic C and nematic phases were observed between 450 and 455 K and 455 and 456 K, respectively, on heating, and between 456 and 455 K (nematic) and 455 and 440 K (smectic C) on cooling from the isotropic liquid phase. The introduction of the heptyloxybiphenoxy groups as side chains into cyclotriphosphazene has generated the liquid crystalline phase. FTIR spectroscopy showed that the P=N and P-O-(C) stretching vibrations converted to lower frequencies from 1224 to 1210 cm^?1 and from 920 to 910cm^?1, respectively, at the crystalline (C)-S_c phase transition. This result suggests that the state of the cyclotriphosphazene ring dramatically changes near the C-S_c phase transition.     

Determination of Antimony(III) and Total Antimony in Aqueous Samples by Electrothermal Atomic Absorption Spectrometry After Dispersive Liquid–Liquid Microextraction (DLLME)

Dispersive liquid–liquid microextraction (DLLME) technique combined with electrothermal atomic absorption spectrometry (ET-AAS) was proposed for determination of antimony(III) and total antimony at very low concentrations in water samples. The N-benzoyl-N-phenylhydroxylamine (BPHA) was used as a chelating agent, and chloroform and ethanol were used as extraction and disperser solvents, respectively. The effect of various experimental parameters on the extraction and determination was investigated. The detection limits (3σ) were 0.005 μg L^?1 for Sb(III) and 0.008 μg L^?1 for total Sb. The developed method was applied successfully to the determination of Sb(III) and total Sb in natural water samples.     

Separation of Samarium(Ⅲ) and Gadolinium(Ⅲ) by A Push-pull Liquid Membrane System

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Liquid crystal gels cross-linked with 1,3,5-tris-(ω-methacryloyloxyalkyloxy)benzenes

A mixture of ω-(4-cyanobiphenyl-4′-yloxy)alkyl methacrylate and 1,3,5-tris-(ω-methacryloyloxyalkyloxy)benzene was heated to 200 °C at 5–10 °C/min. A large, broad exothermic transition peak was observed by differential scanning calorimetry during the first heating process. The transition indicated the formation of a networked polymer, which was then immersed for 24 h in various nematic liquid crystals, such as 4-cyano-4′-pentylbiphenyl, to give liquid crystal gels. The networked polymers and their corresponding liquid crystal gels exhibited different liquid crystal-isotropic transitions. The swelling behaviors of the liquid crystal gels were compared with those of gels cross-linked with 1,6-hexanediol dimethacrylate, trimethylpropane trimethacrylate, and pentaerythritol tetraacetate. The characteristics of liquid crystal gels cross-linked with 1,3,5-tris-(ω-methacryloyloxyalkyloxy)benzenes were studied.     

Immobilization of Pd(II) Catalysts for Cyclopropanation in Ionic Liquid

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Highly efficient Rod-shape Poly(methacrylic acid-co-styrene-codivinylbenzene)High-performance Liquid Chromatographic Column

IntroductionThedevelopmentofahighlyefficientinstillmakingcopolymerhigh-performanceliquidchromatographic(HPLC)column,theso-calledrodshapecontinuouscolumnisthekeyprobleminseparationofenantiomers,proteins,peptides,polymersandsmallmoleculesaswellbecauseofitsexcellentpermeabilityandefficiency.Modifiedpoly(glycidylmethacrylate-co-ethylenedimethacrylate)"'andpoly(styrene--ccrdivinylbenzene)'6rodshapecolumnwerepreparedbyinsilupolymerizationwiththeconfinesofthestainlesssteeltube.Theheightequivalentto…     

Determination of Mercury(II) in Drinking Water by Total Reflection X-ray Fluorescence Spectrometry and Liquid–Liquid Microextraction

The total reflection X-ray fluorescence determination of mercury(II) in drinking water at concentrations of 7?×?10^?2 to 3.0?µg/L is reported. The mercury(II) preconcentration protocol includes directly suspended droplet microextraction with benzene as a molecular iodine complex. The proposed approach is highly selective. The elements Cr, Mn, Fe, Co, Ni, Zn, and Pb at concentrations up to 0.1?g/L did not interfere with the extraction of trace mercury(II). The method is characterized by high sensitivity (limit of detection of 21?ng/L) and suitable reproducibility (relative standard deviation of 0.12 for 100?ng/L). The accuracy of the results was confirmed by recovery and the method of standard addition.     

Switchable Hydrophilicity Solvent-Based Homogenous Liquid–Liquid Microextraction (SHS-HLLME) Combined with GC-FID for the Quantification of Methadone and Tramadol

In this work, a new method based on homogeneous liquid-phase microextraction was developed for the determination of methadone and tramadol. Dipropylamine was used as extraction solvent with switchable hydrophilicity that can be miscible/immiscible upon the addition or removal of CO₂ as a reagent. The effects of operational parameters of the extraction such as volume of acceptor phase, volume of donor phase, pH of donor phase, and ionic strength of solution were investigated. Under optimal conditions, the preconcentration factors, the detection limits and the linearity of the method were achieved in the ranges of 135–138, 1.2 and 4–1000 µg L^?1, respectively. Finally, the proposed method has been successfully applied to the analysis of methadone and tramadol in urine samples. In urine sample, the preconcentration factors were 118 and 122 for methadone and tramadol, respectively. Additionally, calibration curves were found to be linear in the concentration range of 8–1000 µg L^?1 with the r² values better than 0.998. In addition, limits of detection and quantification were 2.4 and 8 µg L^?1, respectively, for both analytes.     

Liquid secondary ion mass spectrometry of several β-diketonates of cobalt(III) and chromium(III)

The positive, liquid secondary ion (LSI) mass spectra of six cobalt(III) and three chromium(III) (β-diketonates ligand = L^?) were examined in a 3-nitrobenzyl alcohol matrix. The complexes of both metals yield clean, matrix-free mass spectra, but there are important differences between them. The cobalt compounds show prominent peaks assignable to the molecular ion, CoL ₃ ⁺ , of the monomeric chelates, together with abundant dimeric ions, such as Co₂L ₄ ⁺ and Co₂L ₃ ⁺ ; in contrast, chromium complexes show protonated monomers, CrL₃H⁺, in addition to ionized monomers, CrL ₃ ⁺ , and only minor formation of dimeric ions. The collisionally-activated dissociation (CAD) mass spectrum of Co₂L ₄ ⁺ shows fragmentation to CoL ₂ ⁺ and Co₂L ₃ ⁺ . That of Co₂L ₃ ⁺ shows fragmentation only to dimeric ions, including Co₂L ₂ ⁺ and, for thienyl or phenyl substituted ligands, to Co₂L₂Ar⁺ or Co₂LAr⁺ (Ar = thienyl or phenyl). Neither Co₂L ₄ ⁺ nor Co₂L ₃ ⁺ dissociates to the CoL ₃ ⁺ ion. The LSI mass spectrum of a mixture of two different cobalt chelates shows dimeric ions containing both types of ligand, which can be explained by ion-molecule reactions in the selvedge region. The differing behaviors of the cobalt and chromium complexes is attributed to the relatively greater stability of the +2 oxidation state for cobalt than for chromium.     

Determination of Mn(Ⅱ) Using l-(2-pyridylazo)-2-naphthol Solid Liquid Extraction Spectrophotometry

A procedure is described for the spectrophotometric determination of Mn(Ⅱ) after extraction with molten paraffin. The complex of Mn(Ⅱ) with l-(2-pyridylazo)-2-naphthol can be extracted quantitatively into paraffin in the range of PH=8.5~10.0. After solidified paraffin is dissolved in CHC1₃, the absorbance is determined at 570nm. Beer's law is obeyed in the range of 0 to lOug Mn/lOml. The linear regression equation is A=0.0032+0.0486C, the relative coefficient r=0.9997.     

Liquid–liquid extraction of thorium(IV) with N-n-heptylaniline from acid media

The extraction behavior of thorium(IV) from sulphuric acid medium with N-n-heptylaniline in xylene. Various parameters like reagent concentration, acid concentration, equilibration time, diverse ions and effect of diluents were studied. Thorium(IV) was selectively extracted and separated from many metal ions. The nature of the extracted species was determined. Thorium(IV) was analyzed from monazite ore and gas mantle.

     

Synthesis of Poly(ethylene glycol) Functionalized Star-shaped Tricationic Imidazolium Based Ionic Liquid

We report on the preparation of a well-defined star-shaped tricationic ionic liquid possessing three arms of poly(ethylene glycol) functionalized imidazolium rings. Remarkable solubility was found in most of the organic solvents we used. Thermogravimetric analysis(TGA) exhibited excellent thermal stability and two distinct decomposition temperatures were attributed to two kinds of chemical degradation. Differential scanning calorimetry(DSC) was further employed to investigate the thermal phase transitions, that three different signals(Tg, Tc, and Tm) were shown upon the second heating process. Moreover, CH2Cl2 solution of the ionic liquid expressed an excitation-wavelength dependent fluorescence response, leading to the facile modulation of photoluminescence behavior. This work represents an example of utilizing molecular design to construct novel ionic liquids and endow further potential to be used in the engineering materials.     

Chemically Laminated 2D Bis(terpyridine)metal Polymer Films: Formation Mechanism at the Liquid–Liquid Interface and Redox Rectification

Recent studies on molecular 2D materials with high tunability of structure and function have focused mostly on the discovery of new precursors. Here, we demonstrate a facile one-pot synthesis of laminated 2D coordination polymer films comprising bis(terpyridine)iron and cobalt at a water/dichloromethane interface. Cross-sectional elemental mapping unveiled the stratum-like structure of the film and revealed that the second layer grows to the dichloromethane side below the first layer. Cyclic voltammetry clarified that the bottom layer mediates charge transfer between the top layer and the substrate in a narrow potential region of mixed-valence states. Furthermore, the bilayer film sandwiched by electrodes in a dry condition shows stable rectification character, and the barrier voltage corresponds to the redox potential difference between the two layers. This study introduces a new strategy for polymer design to explore the materials science of molecular 2D materials.     

Dynamic Rheological Characterization of A Thermotropic Liquid Crystalline Poly (aryl ether ketone)

Poly(aryl ether ketone)s (PAEKs) have been widely used as advanced materials in applications because of their excellent thermal stabilities and good chemical resistance1. The high melt viscosity is one of the major drawbacks in processing them. The synthesis of thermotropic liquid crystalline PAEKs has shed light on the solving of this problem2 because they have been proved to have melt viscosities significantly lower in nematic state than those of the isotropic PAEKs and can be melt proce…     

Speciation Study of Trace Elements by Reversed Phase-High Performance Liquid Chromatography ( Ⅰ )——Simultaneous Determination of Cr( Ⅲ ) and Cr( Ⅵ )

Reported here is the Cr-speciation study by High Performance Liquid Chromatography (HPLC) using precolumn derivatization with ammonium pyrolidinyldithiocarbamate (APDC) and spectrophotometric detection. The rapid and sensitive method has been successfully applied to the analysis of environmental water. The chromatographic behavior of the two Cr-APDC chelates are illustrated with "Solvophobic Theory".     

Carrier‐Mediated Transport of Hg(II) through Bulk and Supported Liquid Membranes

The transport of Hg (II) ions from an aqueous solution into an aqueous receiving solution through bulk and supported liquid membranes containing a calix[4]arene derivative 1 as a carrier was examined. The kinetic parameters of bulk liquid membrane studies were analyzed assuming two consecutive, irreversible first‐order reactions. The influence of temperature, stirring rate, carrier concentration and solvent on the kinetic parameters (k₁, k₂, R_m ^max, t_max, J_d ^max, J_a ^max) has also been investigated. The membrane entrance rate, k₁, and the membrane exit rate, k₂, increased with increasing temperature and stirring rate. The activation energy values are calculated as 4.87 and 48.63 kj mol^?1 for extraction and reextraction, respectively. The values of calculated activation energy indicate that the process is diffusionally controlled by species. Also, the transport behavior of Hg²⁺ from aqueous solution through a flat‐sheet supported liquid membrane has been investigated by the use of calix[4]arene derivative 1 as carrier and Celgard 2500 as the solid support. A Danesi mass transfer model was used to calculate the permeability coefficients for each parameter studied. The highest values of permeability were obtained with 2‐nitrophenyloctyl‐ether (NPOE) solvent and the influence was found to be in the order of NPOE>chloroform>xylene.     

Tetrakis(oxadiazolylphenyl)pyrazines: New St. Andrew′s Cross-Shaped Liquid Crystals

π-Conjugated molecules with the shape of St. Andrew′s cross have been synthesized via fourfold Huisgen reaction. Four 2,5-diaryl-1,3,4-oxadiazol arms are attached to a central pyrazine nucleus. These fluorescent stars, when decorated with a rim of eight alkoxy side chains are discotic liquid crystals. Depending on the substitution pattern, the width of the liquid phase varies within a broad range of 25 °C to 250 °C. In their liquid crystalline phase, the molecules assemble in a typical hexagonal columnar supramolecular arrangement.