Molecularly imprinted adsorbents for preconcentration and isolation of progesterone and testosterone by solid phase extraction combined with HPLC

The use of a novel procedure of solid-phase extraction with molecularly imprinted polymers (MISPE) has been described. A MISPE procedure relying on tailor-made, artificial-mimic materials capable of selectively rebinding target analytes (steroids) based on a combination of recognition mechanisms, such as size, shape and functionality, was custom designed for progesterone and testosterone. The combination of MISPE with LC/DAD is a simple and an efficient method for the determination and quality control of progesterone and testosterone in human urine samples.     

Volumetric Properties of Aqueous Solutions of L-Glutamic Acid and Magnesium-L-Glutamate

Densities of aqueous solutions of L-glutamic acid and magnesium-L-glutamate were determined from T=288.15 to 333.15 K at 5 K temperature intervals. The measured densities were used to evaluate the apparent molar volumes, V _2,φ (m,T), the cubic expansion coefficients, α(m,T), and the changes of isobaric heat capacities with respect to pressure, (∂ C _p /∂ p) _T,m . They were qualitatively correlated with changes in the structure of water that occur when L-glutamic acid or magnesium-L-glutamate are present.     

Synthesis Characterization and Viscosity Studies of Homopolymer of Methyl Methacrylate and Copolymer of Methyl Methacrylate and Styrene

A homopolymer of methyl methacrylate (MMA) and its copolymer with styrene at different compositions were synthesized and characterized. Viscosity measurements of the synthesized homopolymer and the copolymers in toluene solutions were performed at 313 K. Different equations were used to calculate the intrinsic viscosity, viscometric constants values, and molecular weight of the synthesized polymers. The values of intrinsic viscosity and viscosity average molecular weight obtained by the two methods (single point determination and graphical extrapolation) were compared in order to verify the validity of the single point determination for the polymers. Viscometric properties derived included the specific viscosity (it determines the contribution of the solute to the viscosity of the solution), the reduced viscosity (that provides a measure of the polymer capacity for increasing the solution viscosity), and the intrinsic viscosity.     

Stability and Coordination Mode of Complexes of Polyphosphates and Polymetaphosphates with Copper(II) Ions in Aqueous Solution—Potentiometric,Spectral and Theoretical Studies

Complexes of copper(II) with a number of polyphosphate and polymetaphosphate anions have been studied in aqueous solutions by potentiometric, spectroscopic and theoretical methods. Stability constants of the complexes have been determined as well as their coordination modes. Results of the equilibrium studies provided evidence for the formation of ML, MHL and ML(OH) _x type complexes with the ligands studied. The length of the polyphosphate chain was found to affect the oxygen atom charge that is reflected in the stability constants of the ML type complexes. Moreover, the stability of the complex is also influenced by the spatial arrangement of the phosphate groups in phosphates and metaphosphates. The spectral parameters observed for certain complexes have permitted us to deduce the inner coordination sphere of the studied complexes.     

Influence of Europium speciation on its accumulation in Brassica napus and over-expressing BnTR1 lines

This study aimed at influence of europium speciation on its accumulation in Brassica napus (CK) and over-expressing BnTR1 lines (OE), and the kinetics of Eu uptake were investigated. These results indicated that the uptake in the roots of OE was higher than that of CK at high concentrations of europium and even the enrichment in the roots of OE was as high as 20,000 mg/kg at 328.9 μΜ Eu, this suggested that OE might have better resistance to uranium than CK. The time kinetics in plants showed that there had the similar trend between CK and OE. The formation of Eu³⁺at pH 5 in deionized water was beneficial to plants enrichment Eu and carbonate could reduce the adsorption of Eu in two group and phosphate almost completely impress the adsorption of Eu in two group, but citric acid could enhance europium root-to-shoot translocation in two group. These results would help understanding the mechanism of Eu uptake in Brassica napus (CK) and over-expressing BnTR1 lines (OE), therefore properly developing efficient europium/americium phytoremediation.     

Thermal and quality evaluation of vegetable oils used in ruminant feed

Dairies add fat supplements to the diets of small ruminants to increase energy production and consequently the production and quality nutritional and sensorial of the milk. This study investigated the thermal and oxidative stability of babassu, castor, faveleira, and sesame oils by TG/DTA and PDSC. The profile of the fatty oils studied was determined by GC–MS as well as physicochemical characteristics. The thermogravimetric profile of the oils indicated that mass loss was caused by the decomposition or volatility of the triacylglycerides. Faveleira and sesame oils showed a high percentage of polyunsaturated fatty acids, especially C18:2. From a nutritional standpoint, unsaturated oils are more suitable supplements for animals because they promote biochemical changes beneficial to human health.     

Volumetric Properties of Some Aliphatic Mono- and Dicarboxylic Acids in Water at 298.15 K

The apparent molar volumes, V _φ , of two series of homologous aliphatic carboxylic acids, H(CH₂) _n COOH [n=0–5] and (CH₂) _n (COOH)₂ [n=0–5], were determined in dilute aqueous solutions by density measurements at T=298.15 K. Densities were measured using a vibrating-tube densimeter (DMA 5000, Anton Paar, Austria) at T=298.15 K. These results were used to calculate the apparent molar volumes of each solute over the concentration range 0.0050≤m/(mol⋅kg⁻¹)≤0.3000. Values of the apparent molar volumes of undissociated acids V_f(u)⁰V_{\phi (u)}^{0} were also calculated. The variation of V_f(u)⁰V_{\phi (u)}^{0} was determined as a function of the aliphatic chain length of the studied carboxylic acids.     

Intramolecular Charge Transfer Reaction in Solutions of Low to High Electrolyte Concentrations: Interplay between Friction and Solvation

Fluorescence emission spectroscopy have been used to investigate the effects of electrolytes on the excited state intramolecular charge transfer (ICT) reaction in 4-(1-azetidinyl)benzonitrile (P4C) in very dilute to concentrated electrolyte solutions of ethyl acetate (EA), acetonitrile (AN) and ethanol (EtOH). In the limit of very low electrolyte concentrations, the reaction rate (=1/τ _rxn, τ _rxn being the reaction time) is found to decrease with increasing electrolyte concentration, the extent of decrease being the maximum in EA and the minimum in AN. At moderate to higher electrolyte concentrations, however, the rate increases upon further addition of electrolyte. The observed non-monotonic electrolyte concentration dependence of rate is believed to occur due to a novel interplay between friction and solvation experienced by the photo-excited reactant in solution. Moreover, the long time decay constant and amplitude of the bi-exponential decay of the time resolved fluorescence emission intensity also show a significant electrolyte concentration dependence which corroborates the relevant steady-state results. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Densities and Excess Molar Volumes of Binary and Ternary Mixtures Containing Acetonitrile + Acetophenone + 1,2-Pentanediol: Experimental Data,Correlation and Prediction by PFP Theory and ERAS Model

Densities were determined experimentally over the entire range of composition at 298.15 K for the ternary system acetonitrile (1) + acetophenone (2) + 1,2-pentanediol (3) and for the three corresponding binary systems. Excess molar volumes were calculated for the binary and the ternary systems. These results were fitted to variable-degree polynomials. Further, the Prigogine-Flory-Patterson (PFP) theory and Extended Real Associated Solution (ERAS) model were applied to V_m^EV_{m}^{\mathrm{E}} for the binary mixtures of acetonitrile + acetophenone, acetonitrile + 1,2-pentanediol and acetophenone + 1,2-pentanediol, and the findings compared with the experimental results.     

Ultrasonic Velocities,Densities, and Refractive Indices of Binary Mixtures of Polyethylene Glycol 250 Dimethyl Ether with 1-Propanol and with 1-Butanol

Measurements of the ultrasonic velocity (u), density (ρ) and refractive index (n) for binary mixtures of polyethylene glycol 250 dimethyl ether with 1-propanol and 1-butanol have been made at three temperatures (T=293, 303 and 31 K) over the entire composition range in order to investigate the nature of intermolecular interactions between the components of these liquid mixtures. Various excess thermodynamic properties such as the excess ultrasonic velocity (Δu), deviation in isentropic compressibility (Δk _S ), excess intermolecular free length (L_f^E)(L_{\mathrm{f}}^{\mathrm{E}}), excess acoustic impedance (Z ^E), excess pseudo-Grüneisen parameter (Γ ^E), and molar refraction deviation (ΔR _m) were calculated using experimental values of the ultrasonic velocity, density and refractive index and were then represented with the Redlich-Kister polynomial equation. The observed excess deviation parameter values were explained on the basis of the strength of intermolecular interactions between the components of the mixtures. Estimations of the refractive index and ultrasonic velocity have also been made using various empirical relations and are discussed in terms of the average percentage deviations (APD).     

Conductance of Dilute Hydrochloric Acid Solutions to 458 K and 1.4 MPa

Electrical conductance measurements were made on dilute solutions of hydrochloric acid to 458 K and 1.4 MPa with a flow instrument. These measurements agree well with those of previous authors. The conductance theory of Fuoss and Hsia as given by Fernandez-Prini (FHFP), was fit to these measurements. It was found that this theory adequately described the present results with a single parameter, the limiting conductance at infinite dilution Λ°(HCl). Within their estimated accuracy, reported literature results of Λ°(HCl) between 264.15 and 579 K and high pressures were found to be represented by a five-parameter equation that was a function of the solvent viscosity, temperature and pressure. This equation along with the FHFP theory permits accurate calculation of the conductance of dilute hydrochloric acid solutions at high temperatures and pressures. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Temperature Dependence of Physical Properties of Imidazolium Based Ionic Liquids: Internal Pressure and Molar Refraction

Density, speed of sound and refractive index of the imidazolium-based ionic liquids (ILs), 1-methyl-3-octylimidazolium chloride [C₈mim][Cl], 1-butyl-3-methylimidazolium methyl sulfate [C₄mim][C₁OSO₃], and 1-butyl-3-methylimidazolium octyl sulfate [C₄mim][C₈OSO₃], have been measured in the temperature range from 283.15 to 343.15 K. Experimental density and speed of sound have been used to calculate the internal pressure p _i of the ILs. The p _i values were found to be higher than those of water and molecular organic liquids, but lower than those of classical molten salts. We also calculated molar refraction R _M from the measured refractive index n _D in the temperature range from 288.15 to 343.15 K. Refractive indices of ILs were also higher than those of normal organic liquids, but comparable to long-chain hydrocarbon organic solvents. The structure-property correlation of the ILs has been discussed and the results have been compared to our earlier studies (Kumar in J. Solution Chem. 37:203–214, 2008).     

Magnesiation of N-Heterocycles Using i-PrMgCl · LiCl and Catalytic Diisopropylamine

The direct magnesiation of various N-heterocyclic compounds with i-PrMgCl · LiCl and catalytic diisopropylamine allows for preparation of 2-substituted pyrroles, imidazole, indoles, and benzimidazoles, in moderate to good yields. The magnesiated substrates canreadily undergo a Kumada-type coupling with iodo-aryls in the presence of catalytic Pd(PPh₃)₄.     

A Structural and Calorimetric Study on the Interaction Between Jack Bean Urease and Cyanide Ion

The cyanide ion was studied as an effecter of Jack bean urease at 300 K in 30 mmol⋅L⁻¹ Tris buffer, pH=7. The inhibition was investigated by isothermal titration calorimetry (ITC). The extended solvation model was used for CN⁻+JBU interaction over the whole range of CN⁻ concentrations. The binding parameters recovered from the solvation model were attributed to the interaction with cyanide ion. It was found that cyanide ion acted as a noncooperative inhibitor of urease, and there is a set of 12 identical and independent binding sites for CN⁻ ions. The dissociation equilibrium constant is 749.99 μmol⋅L⁻¹. The molar enthalpy of binding is ΔH=−13.60 kJ⋅mol⁻¹.     

Coordination Features of a Polyaza-Bipyridine-Macrocyclic Ligand toward Co(II) and Cd(II) in Water and Dimethylsulfoxide

The coordination features of a polyaza macrocycle, containing the diverse bipyridine unit 4,4′-(2,5,6,11,14-pentaaza[15]-[15](2,2′)-bipyridylophane (L3), with Co(II) and Cd(II) have been studied in aqueous solution and in the aprotic solvent dimethylsulfoxide (DMSO). The study was carried out at 298 K by means of potentiometric, spectrophotometric and calorimetric techniques. The formation of the dinuclear species M₂ L3 is observed for Co(II) both in water and in DMSO, whereas Cd(II) is able to form this type of dinuclear complex only in DMSO. The FT-IR spectra of the mononuclear species ML3, formed in both solvents, provide evidence that the rigid structure of the polyaminic chain prevents metal ions from being coordinated by all of the nitrogens of the macrocyclic cavity, in good agreement with the behavior suggested by the thermodynamic parameters. The results are compared with those for the complexation of Co(II) and Cd(II) with similar polyazamacrocycles containing a bipyridine unit directly inside the cavity. Semi-empirical calculations were also performed to obtain structural information.     

The synthesis and characterisation of novel dimethyl- and diphenyl-silanediolates

Dimethyl- and diphenylsilanediolates are key intermediates in the preparation of dimethyl- and diphenyl-siloxane polymers. Both dimethyl- and diphenylsilanediolates R₂Si(OM)₂, where R = Me or Ph, and M = Li, Na and K were synthesised by the reaction between dimethyl- and diphenylsilanediol and a metal or metal hydride (M/MH where M = Li, Na and K). The silanediolates were characterised by ²⁹Si, ¹³C and ¹H NMR, FTIR and mass spectroscopy.     

Competitive Self and Induced Aggregation of Calix[4]arene Ethers and Their Interaction with Pinacyanol Chloride and Methylene Blue in Nonaqueous Media

Long chain calix[4]arene ethers have been examined for aggregation in nonaqueous solvents by using UV-vis molecular absorbance spectroscopy. It has been observed that tetraalkylated (alkyl = hexadecyl and octadecyl, respectively) calix[4]arene ethers tend to aggregate in chloroform and tetrahydrofuran, possibly via π–π stacking interactions of the phenyl moieties, and the aggregation process appears to be facilitated by the alkyl chains. The analogous dialkylated compounds do not show any self-aggregation, plausibly due to strong hydrogen bonding between the –OH and the –O– of calix aryl ether which seems to disrupt the aggregation process. Addition of the anionic surfactant sodium dodecylsulfate (SDS) appears to hinder the aggregation process in nonpolar chloroform but the same surfactant facilitates aggregation in the polar tetrahydrofuran. The cationic surfactant (cetyltrimethyl ammonium bromide) and the nonionic surfactant (Brij-35) have no effect on this aggregation process. Unexpectedly, SDS induces aggregation of dialkylated calix[4]arene ethers in chloroform. It has been observed that the aggregated form of the tetraalkylated calix[4]arene ethers tend to increase the dimerization efficiency of cationic dyes (pinacyanol chloride and methylene blue) in chloroform.     

Adsorption and Inhibition Effect of Benzaldehyde Schiff Bases on Mild Steel Corrosion in 1 M HCl Medium

This article has been retracted.     

Measurement of Magnesium Stability Constants of Biologically Relevant Ligands by Simultaneous Use of pH and Ion-Selective Electrodes

Simultaneous measurements with magnesium ion-selective and pH glass electrodes have been used for determination of the stability constants of magnesium ions with various biologically relevant ligands by alkalimetric titration under physiological conditions (37^○C, I=0.15 mol⋅dm⁻³). New systems were investigated: magnesium with pyroglutamate, pyridoxine and HEPES, along with citrate, lactate, glycinate, aspartate and glutamate. For comparison, calcium stability constants with the same ligands were determined similarly, using calcium ion-selective and pH glass electrodes. Ligand protonation constants, necessary for the calculation of the metal complex formation constants, were also determined.     

Adsorption properties of BEA zeolites and their aluminum phosphate extrudates for purification of isomaltose

The disaccharide isomaltose is produced via an enzymatic reaction and is adsorbed to BEA zeolite. This reaction integrated adsorption can be achieved as fluidized bed as well as fixed bed. We investigated isotherms, adsorption enthalpies and sorption kinetics of BEA zeolite and extrudates with a novel aluminum phosphate sintermatrix. These extrudates contain 50% (w/w) of BEA 150 zeolites (Si/Al = 75) as primary crystals. BET-surface for extrudates is 245 m²⋅g⁻¹ and 487 m²⋅g⁻¹ for zeolite. Extrudates show a monomodal macropore structure with a maximum at 90 nm. All isotherms show a type I shape. For lower equilibrium concentrations, which occur during the enzymatic reaction, Henry’s law is applied and compared to a Langmuir model. Adsorption equilibrium constant K _i,L calculated from Langmuir for extrudates at 4 °C is 64.7 mL⋅g⁻¹ and more than twice as high as obtained from Henry’s law with K _i is 26.8 mL⋅g⁻¹. Adsorption on extrudates at 4 °C is much stronger than on zeolite crystals where the Henry coefficient K _i is 17.1 mL⋅g⁻¹. Adsorption enthalpy Δh _Ad calculated from van’t Hoff plot with the Henry equation is −44.3 kJ⋅mol⁻¹ for extrudates and −29.6 kJ⋅mol⁻¹ for zeolite crystals. Finally, the kinetics for ad- and desorption were calculated from the initial slope. The diffusion rate for ad- and desorption on extrudates were in the same range while adsorption on zeolites is three orders of magnitudes faster than desorption.