Mechanism of change in enantiomer migration order of enantioseparation of tartaric acid by ligand exchange capillary electrophoresis with Cu(II) and Ni(II)-D-quinic acid systems

The mechanism of change in the enantiomer migration order (EMO) of tartarate on ligand exchange CE with Cu(II)- and Ni(II)-D-quinic acid systems was investigated thoroughly by circular dichroism (CD) spectropolarimetry. The (13) C NMR spectra of solutions containing D-quinate (pH 5.0) with Cu(II) or Ni(II) revealed the coordination of carboxylate and hydroxyl groups on D-quinate. The D-quinic acid concentration dependence of the CD spectra at a fixed Cu(II) concentration at pH 5.0 indicates that the 1:1, 1:2 and 1:3 Cu(II)-D-quinate complexes were formed with an increase in the concentration of D-quinic acid. The CD spectral behavior revealed that D-tartarate is selectively coordinated to the 1:1 complex to give the 1:1:1 Cu(II)-D-quinate-D-tartarate ternary complex while L-tartarate is selectively bound to the 1:2 and 1:3 complexes to form the 1:2:1 ternary complex. In the Ni(II)-D-quinic acid system, it became apparent that the 1:2 Ni(II)-D-quinate complex is mainly formed in the wide range of D-quinic acid concentration at pH 5.0 and D-tartarate is selectively coordinated to the 1:2 complex to form the 1:2:1 ternary complex. The change in EMO of tartarate on ligand exchange CE was explainable by the change in coordination selectivity for D- and L-tartarates in the Cu(II)- and Ni(II)-D-quinic acid systems depending on the compositions of the complexes formed in BGE.     

SULFATION OF PACHYMAN WITH CHLOROSULFONIC ACID USING THE IMPROVED WOLFROM METHOD

High purity polysaccharide of pachyman was isolated from the powder of Poria cocos sclerotium with an yield of 77.8%. The intrinsic viscosity of polysaccharide was found to be 78.95 mL/g in DMSO solution at 25℃. The isolated polysaccharide was reacted with chlorosulfonic acid to obtain pachyman sulfate using the improved Wolfrom method. The results of the orthogonality experiment on the sulfation reaction identified that the effectiveness of the reaction conditions on the degree of sulfation and the value of intrinsic viscosity is in the following order: molar ratio of chlorosulfonic acid to glucoside (3-5) ＞ reaction temperature (60-80℃) ＞ reaction time (1-2 h). The kinetic studies of the pachyman sulfationindicated that the hydrolysis is accompanied with the sulfation process. The decrease in intrinsic viscosity of the sulfated pachyman is proportional to the increase in the degree of sulfation under the mild reaction conditions of ＜ 80℃,chlorosulfonic acid/glucoside mole ratio ＜ 5, and reaction time ＜ 2 h. Beyond the above reaction conditions, excessive loss of -OH group occurs during hydrolysis. The NMR results indicated a complete sulfation on C-6 and a partial sulfation on the C-2 and C-4 of glucoside.     

Selectivity comparison of acetonitrile-methanol-water ternary mobile phases on an octadecylsiloxane-bonded silica stationary phase

The solvation parameter model was used in this study to investigate various intermolecular interactions that influence retention on the standard C18 stationary phase for the solvent system acetonitrile:methanol (ACN:MeOH, 1:1). In comparison to the organic mobile phase modifiers acetonitrile, acetone, methanol, 2-propanol, and tetrahydrofuran, the solvent strength for the ACN:MeOH (1:1) solvent system was evaluated. To facilitate the interpretation of various intermolecular interactions that contribute to retention on a standard C18 stationary phase for the solvent system ACN:MeOH (1:1), system maps were constructed and compared with those of acetone, tetrahydrofuran, acetonitrile, 2-propanol, and methanol. The solvation parameter models were constructed for the ternary solvent system ACN:MeOH (1:1)-water, and in the models constructed, the coefficient of determination values were from 0.998 to 0.999, the Fisher statistic values for the models were from 1687 to 4015, and the standard error of the estimate values ranged from 0.022 to 0.029. The solvent system ACN:MeOH (1:1) has retention properties more similar to methanol than acetonitrile, indicating methanol's influence is more dominant.     

Dependence of selective enclathration on types of cholic acid crystals

Competitive recrystallizations of cholic acid (CA) from 1:1 binary mixtures of seven mono-substituted benzenes are demonstrated. The order of preference for guests to be incorporated into the cholic acid crystals are as follows: benzene, toluene > n-amylbenzene, n-hexylbenzene > ethylbenzene, n-propylbenzene, n-butylbenzene. These seven compounds afford bilayer type inclusion crystals that are classified into four types based on the host frameworks and host-guest stoichiometries. The order of selective enclathration corresponds to the four types as follows: 1:1 alpha G > 2:1 alpha G > 1:1 beta T or 2:1 alpha T. The preference for the alpha G type was also confirmed by investigating the host frameworks of the crystals obtained from binary mixtures. The dependence of the selectivity on the different types of CA crystals can be understood in terms of the fit of the guest molecule in the host cavity.     

Complexation of vanadium(IV) with organic reagents on the solid phase of fibrous ion exchangers according to diffuse reflectance and EPR data

Diffuse reflectance and EPR spectroscopic data are reported for the formation of vanadium complexes with the organic reagents (ORs) sulfochlorophenol S (SCP) and pyridylazoresorcinol (PAR) on the solid phase of polyacrylonitrile fiber filled with the cation exchanger KU-2 or the anion exchanger AV-17 or A-5. The effects of the order of sorption of the reaction components, sorption conditions, and the V: OR ratio on the complexation process are discussed. The characteristics of the complexes obtained on the solid phase and in solution are compares. Both M : OR = 1 : 1 and M : OR = 2 : 1 SCP complexes can form on the solid phase without involving any croups of the matrix. PAR forma a 1 : 1 complex involving groups of the A-5 matrix.     

Interactions of cholesterol with cyclodextrins in aqueous solution

The interaction of cholesterol with several cyclodextrins (CDs) was investigated in water using solubility method. It was found that heptakis (2,6-di-O-methyl)-beta-CD (DOM-beta-CD) forms two types of soluble complex, with molar ratios of 1 : 1 and 1 : 2 (cholesterol : DOM-beta-CD), and neither a soluble nor insoluble complex is formed between cholesterol and alpha-CD, beta-CD, and gamma-CD, although a minor soluble complex formation was observed between cholesterol and 2-hydroxylpropyl-beta-CD. The thermodynamic parameters for 1 : 1 and 1 : 2 complex formation of cholesterol with DOM-beta-CD obtained from the changes in K with temperature are as follows: DeltaG degrees (1 : 1)=-11.6 kJ/mol at 25 degrees C (K(1 : 1)=1.09x10(2) M(-1)); DeltaH degrees (1 : 1)=-3.38 kJ/mol; TDeltaS degrees (1 : 1)=8.25 kJ/mol; DeltaG degrees (1 : 2)=-27.1 kJ/mol at 25 degrees C (K(1 : 2)=5.68x10(4) M(-1)); DeltaH degrees (1 : 2)=-3.96 kJ/mol; and TDeltaS degrees (1 : 2)=23.2 kJ/mol. The formation of the 1 : 2 complex occurred much more easily than that of the 1 : 1 complex. The driving force for 1 : 1 and 1 : 2 complex formation was considered to be mainly hydrophobic interaction. Also, based on the measurements of proton nuclear magnetic resonance spectra and studies with Corey-Pauling-Koltun atomic models, the probable structutures of the 1 : 2 complex were estimated.     

Quantum-chemical study on the catalytic activity of TinRumO2(1 1 0) surfaces on chlorine evolution

Based on the generalized gradient approximation (GGA), Perdew-Wang-91 (PW91) combined with a periodic slab model has been applied to study the catalytic activity of chlorine evolution on TinRumO2(1 1 0) surface. Metal oxide model TinRumO2 has been established with pure TiO2 and RuO2 on the basis set of Double Numerical plus polarization (DNP), in which the proportion of n:m was 3:1, 1:1, or 1:3. Analysis on the reaction activity in the electrochemical reaction and the electrochemical desorption reaction was based on Frontiermolecular orbital theory. The results show that the TinRumO2 with a ratio of Ti:Ru at 3:1 is best facilitates the electrochemical reaction and electrochemical desorption reaction to produce M-Clads intermediate and precipitate Cl2. In addition, the adsorption energy of Cl on the surface of Ti3Ru1O2 possesses the minimum value of 2.514 eV, and thus electrochemical desorption reaction could occur most easily.     

Complex formation of nonsymmetric 1,2-diacylhydrazines with nonferrous metal ions

Complex formation of Cu(II), Co(II), Ni(II), and Zn(II) ions with nonsymmetric 1,2-diacylhydrazines (DAHs) in ammonia solutions was studied. [M(II): [DAH] ratios were found by equilibrium slope, isomolar series, and conductometric titration methods to be 1: 1 and 1: 2 for Cu(II), 2: 1 and 1: 1 for Co(II), 2: 1 and 1: 1 for Ni(II), and 1: 1 for Zn(II). Independent of the [M(II): [DAH] ratio, we have isolated only complexes of composition 1: 1 from ammonia solutions. The composition was confirmed by IR spectroscopy and elemental analyses. The solubility products of solid complexes of 1: 1 composition and the complex formation constants were calculated with considering the states of ligands and metal ions in ammonia solutions. The solubility products of the solid complexes were found to depend on the length of radical in DAHs.     

Carbon-supported Pd-Co as cathode catalyst for APEMFCs and validation by DFT

Carbon supported PdCo catalysts in varying atomic ratios of Pd to Co, namely 1 : 1, 2 : 1 and 3 : 1, were prepared. The oxygen reduction reaction (ORR) was studied on commercial carbon-supported Pd and carbon-supported PdCo nanocatalysts in aqueous 0.1 M KOH solution with and without methanol. The structure, dispersion, electrochemical characterization and surface area of PdCo/C were determined by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Cyclic Voltammetry (CV), respectively. The electrochemical activity for ORR was evaluated from Linear Sweep Voltammograms (LSV) obtained using a rotating ring disk electrode. The catalysts were evaluated for their electrocatalytic activity towards oxygen reduction reaction (ORR) in Alkaline Polymer Electrolyte Membrane Fuel Cells (APEMFCs). PdCo(3 : 1)/C gives higher performance (85 mW cm(-2)) than PdCo(1 : 1)/C, PdCo(2 : 1)/C and Pd/C. The maximum electrocatalytic activity for ORR in the presence of methanol was observed for PdCo(3 : 1)/C. First principles calculations within the framework of density functional theory were performed to understand the origin of its catalytic activity based on the energy of adsorption of an O(2) molecule on the cluster, structural variation and charge transfer mechanism.     

Improvements in glass capillary gas chromatographic polychlorobiphenyl analysis

Separation of a 1:1:1:1 calibration mixture of Aroclors 1221, 1016, 1254, and 1260 on soda glass capillaries coated with Apolane (C-87) or Apiezon L is described. Polychlorobiphenyl congener structures are assigned to 112 separated and partially separated zones. The quantitative composition of Aroclor 1221 is reported. The performance of the two stationary phases on different lengths of laboratory and commercially prepared capillaries is compared and found to be very similar. Aroclors 1221, 1016, 1254, and 1260 are employed (1:1:1:1) for the primary calibration mixture because they contain all components of the commercial materials which pollute the environment; they are also easily obtained from the U.S. EPA Repository so that the method can be used in any laboratory by employing the calibration data given here.     

Investigation of picramic acid and methylguanidine formation during the heated Jaffe' reaction

The present study has confirmed the formation of picramic acid and methylguanidine during the heated Jaffe' reaction. Picramic acid was isolated on thin-layer chromatography from 0.5:1 and 1:1 heated creatinine:picric acid molar ratio test solutions, but not for similarly performed 3:1 test solutions. A Dowex column was employed to isolate methylguanidine from 0.5:1 and 3:1 molar ratio test solutions. Methylguanidine was similarly isolated from a heated alkaline creatinine solution.     

Rapid dioxin assessment in fish products by fatty acid pattern recognition

A novel, cost- and time-effective dioxin screening method relying on fatty acid profile was developed for fish products. The method is based on multivariate covariance between fatty acid composition and dioxin. A dioxin range varying from 1.1 to 47.1 ng TEQ-WHO kg fat(-1) was investigated using 64 fish meal samples. An optimal multivariate dioxin prediction model was developed based on reduction from the original 32 to 13 fatty acids, thus increasing the parsimony and the robustness of the model. The model obtained with three partial least squares regression (PLS) components included the following 13 fatty acids: C14:1 n-5, C16:4 n-1, C18:1 n-9, C18:2 n-6, C18:3 n-6, C18:3 n-3, C20:0, C20:1 n-9, C20:4 n-6, C20:3 n-3, C22:1 n-7, C22:6 n-3, C24:1 n-9. Considering the whole investigated dioxin range, the performance of the PLS model based upon full cross-validation yielded a correlation of 0.90 (r(2)) and a prediction error of 3.31 ng PCDD/F TEQ-WHO kg fat(-1). A submodel of samples in the lower dioxin range 1 to 15 ng PCDD/F TEQ-WHO kg fat(-1) returned a r(2) of 0.88 and an error of 1.85 ng PCDD/F TEQ-WHO kg fat(-1).     

Membrane properties of binary and ternary systems of ganglioside GM1/dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine

The membrane properties of the ganglioside GM1 (GM1)/dioleoylphosphatidylcholine (DOPC) binary system and GM1/dipalmitoylphosphatidylcholine (DPPC)/DOPC ternary system were investigated using surface pressure measurements and atomic force microscopy (AFM), and the effect of surface pressure on the properties of the membranes was examined. Mixed GM1/DPPC/DOPC monolayers were deposited on mica using the Langmuir-Blodgett technique for AFM. GM1 and DOPC were immiscible and phase-separated. The AFM image of the GM1/DOPC (1:1) monolayer showed island-like GM1 domains embedded in the DOPC matrix. There was no morphological change on varying surface pressure. The surface pressure-area isotherm of the GM1/DPPC/DOPC (2:9:9) monolayer showed a two-step collapse as in the DPPC/DOPC (1:1) monolayer. The AFM image for the GM1/DPPC/DOPC monolayer showed DPPC and GM1 domains in the DOPC matrix, and the DPPC-rich phase containing GM1 showed a percolation pattern the same as the GM1/DPPC (1:9) monolayer. The percolation pattern in the GM1/DPPC/DOPC monolayer changed as the surface pressure was varied. The surface pressure-responsive change in morphology of GM1 was affected by the surrounding environment, suggesting that the GM1 localized in each organ has a specific role.     

Simultaneous kinetic-spectrophotometric determination of periodate-bromate and iodate-bromate mixtures using the H-point standard addition method

The H-point standard addition method (HPSAM), based on spectrophotometric measurement, for simultaneous determination of periodate-bromate and iodate-bromate mixtures is described. This method is based on the difference between the rates of their reactions with iodide in acidic media. The results showed that simultaneous determinations could be performed with the ratio 1:15-12:1 for periodate-bromate and 15:1-1:15 for iodate-bromate. The proposed method was successfully applied to the simultaneous determination of periodate-bromate and iodate-bromate in water and synthetic samples.     

Synthesis and characterization of 3,3,10,10-tetramethyl-1,5,8,12-tetraazacyclotetradecane. A new route to macrocyclic polyamides and polyamines

The 1:1 and 2:2 cyclization reactions were simultaneously observed by addition of diethyl oxalate on 3,3,10,10-tetramethyl-1,5,8,12-tetraazadodecane. The resulting 1:1 cyclisation product was fully characterized by spectroscopy and X-ray diffraction study. The reduction of this compound gives the 3,3,10,10-tetramethyl-1,5,8,12-tetraazacyclotetradecane with a high yield.     

Interaction of heptakis (2,3,6-tri-O-methyl)-beta-cyclodextrin with cholesterol in aqueous solution

The interaction of cholesterol with heptakis (2,3,6-tri-O-methyl)-beta-cyclodextrin (TOM-beta-CyD) was investigated in water using solubility method. It was found that TOM-beta-CyD forms two kinds of soluble complexes, with molar ratios of 1:1 and 1:2 (cholesterol:TOM-beta-CyD). The thermodynamic parameters for 1:1 and 1:2 complex formation of cholesterol with TOM-beta-CyD were: DeltaG0(1:1)=-11.0 kJ/mol at 25 degrees C (K1:1=7.70 x 10 M(-1)); DeltaH0(1:1)=-1.28 kJ/mol; TDeltaS0(1:1)=9.48 kJ/mol; DeltaG0(1:2)=-27.8 kJ/mol at 25 degrees C (K1:2)=7.55 x 10(4) M(-1)); DeltaH0(1:2)=-0.57 kJ/mol; TDeltaS0(1:1)=27.3 kJ/mol. The formation of the 1:2 complex occurred much more easily than that of the 1:1 complex. The driving force for 1:1 and 1:2 complex formation was suggested to be exclusively hydrophobic interaction. Based on the measurements of proton nuclear magnetic resonance spectra and studies with Corey-Pauling-Koltun atomic models, the probable structures of the 1:2 complex were estimated. In addition, the interaction of TOM-beta-CyD with cholesterol was compared with that of heptakis (2,6-di-O-methyl)-beta-CyD (DOM-beta-CyD). The interaction of TOM-beta-CyD is more hydrophobic than that of DOM-beta-CyD, and the life time of the complexed TOM-beta-CyD is sufficiently long to give separated signals, at the NMR time scale, which differs from that of complexed DOM-beta-CyD.     

Testing the effect of the cavity size and the number of molecular substitutions in host–guest complexes formed by 2-hydroxypropyl-cyclodextrins and n-octyl-β-d-glucopyranoside

The thermodynamic characterization of host–guest complex formation processes based on modified cyclodextrins (CDs) presents several difficulties that are absent when using native CDs. They are mainly due to the relatively wide distribution of the degree of molecular substitution and also to the indeterminacy in the location of the modified groups. A more common trouble would arise from the coexistence of coupled processes, such as CD-surfactant complexation and surfactant demicellization. In the present work a reasonable approach based on the analysis of isothermal titration calorimetric measurements is employed to assess the effect of the number of molecular substitutions as well as of the CD cavity size in supra-molecular complexes formed by 2-hydroxypropyl-CDs and n-octyl-β-d-glucopyranoside. The employed method considers both first- (1:1) and second-order (1:2 and 2:1) stoichiometries. The results were significantly different from those previously observed for native CDs. The substituted groups increase entropically the stability of 1:1 species based on α-CD, while compete with the surfactant for the CD cavity in the case of 1:1 and 1:2 species based on β- and γ-CD, respectively. Also, the modified β-CD seems to enhance the formation of non-inclusion second-order complexes.     

Asymmetric induction from a tetrahydropyranyl group on addition of tetrahydropyranyl-oxy-(Z)-allylboronates to aldehydes

A novel type of asymmetric induction originating from the chiral center of a THP protecting group was observed. The induction amounted to a 14:1 diastereoselection on addition of 1 to ethyl pyruvate. Selectivities of 3:1 to 13:1 were observed on addition of 5 to various aldehydes.     

Effect of membrane composition on surface states of ganglioside GM1/dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine monolayers

The surface states of ganglioside GM1 (GM1)/dipalmitoylphosphatidylcholine (DPPC)/dioleoylphosphatidylcholine (DOPC) monolayers having various compositions were investigated using atomic force microscopy (AFM), and the effect of the composition on the surface states of the membrane was examined. The AFM images for the ternary system showed a DPPC-rich phase containing GM1 in the DOPC matrix, which indicated that the morphology varied as the composition of the monolayers changed. The AFM images for the GM1/DPPC/DOPC monolayers having (2:9:9) and (4:18:9) molar ratios showed a percolation pattern similar to that observed for the GM1/DPPC (1:9) monolayer. The AFM image for the GM1/DPPC/DOPC (2:18:9) monolayer showed a dotted pattern with a high topography. Monolayers having a higher content of DOPC than DPPC and/or having a higher content of GM1 showed dot-like domains in the DPPC-rich phase containing GM1. In conclusion, the surface states of GM1/DPPC/DOPC monolayers changed depending on the composition. These results may be related to a diversity of GM1 in various organs.     

Properties of propoxy-derivatives based on the acidic fraction of coconut oil

Hydrolysis of coconut oil was carried out with alkali, and acid fraction was separated. The obtained acid fraction was propoxylated with propylene oxide at 1:1, 1:3, 1:5, and 1:7 molar ratios and 140?150°C. Physico-chemical as well as surface activity parameters of these propoxylates have been determined. Petroleum-collecting and petroleum-dispersing properties of the propoxylates have been studied on thin oil slick on the surface of water with varying degrees of mineralization. The influence of various factors (petroleum layer thickness, the water salinity, and the nature of petroleum) on petroleum-collecting and petroleum-dispersing properties was studied.