Miscibility in systems containing aqueous solutions of various alkylbenzenesulfonates, toluene and, n-butanol

Miscibility relationships in four-component systems containing sodium alkylbenzenesulfonates, toluene, n-butanol, and water were studied at 25°C in the hope of clarifying the complex systems used in the “micellar flood” enhanced oil recovery process. Phase boundary curves for the pseudo three-component systems (constant sulfonate/water ratios, 2.5 moles sulfonate per kg water) were determined. The sulfonates included those of benzene, toluene, xylene, ethylbenzene, isopropylbenzene, mesitylene, cymene, methyl-t-butylbenzene, and diisopropylbenzene, in all of which the alkyl substituents are smaller than in the usual surfactants. The phase boundary curves have similar and fairly symmetrical shapes. The amount of n-butanol (cosolvent) required to produce miscibility decreases with increasing number of alkyl carbons on the benzene ring of the sulfonates and seems relatively independent of the isomeric structure. The sodium salt of diisopropylbenzenesulfonate gives the lowest phase boundary curve (least n-butanol required for miscibility) among the nine sulfonates studied.     

Electrical conductivity measurements of aqueous sodium chloride solutions to 600°C and 300 MPa

Electrical conductance measurements of dilute (<0.1>^–1) aqueous NaCl solutions were made primarily to quantify the degree of ion association which increases with increasing temperature and decreasing solvent density. These measurements were carried out at temperatures from 100 to 600°C and pressures up to 300 MPa with a modified version of the apparatus used previously in the high temperature study in this laboratory. Particular emphasis was placed on conditions close to the critical temperaturelpressure region of water, i.e., at 5° intervals from 370 to 400°C. The results verify previous findings that the limiting equivalent conductance A_o of NaCl increases linearly with decreasing density from 0.75 to 0.3 g-cm^–1 and also with increasing temperature from 100 to 350°C. Above 350°C. A_o is virtually temperature independent. The logarithm of the molal association constant as calculated exclusively from the data400°C is represented as a function of temperature (Kelvin) and the logarithm of the density of water (g-cm^–3) as follows:

Influence of hydrolyzable metal ions on the interfacial chemistry, particle interactions, and dewatering behavior of kaolinite dispersions

The influence of hydrolyzable metal ions (Mn(II) and Ca(II)) adsorption on the surface chemistry, particle interactions, flocculation, and dewatering behavior of kaolinite dispersions has been investigated at pH 7.5 and 10.5. Metal ion adsorption was strongly cation type- and pH-dependent and significantly influenced the zeta potential, anionic polyacrylamide-acrylate flocculant (PAM) adsorption, shear yield stress, settling rate, and consolidation of kaolinite slurries. The presence of Mn(II) and Ca(II) ions alone led to a systematic reduction in zeta potential due to specific adsorption of positively charged metal ion-based hydrolysis products at the kaolinite-water interface. Metal ion-mediated zeta potential changes were reflected by lower dispersion shear yield stresses and improved clarification (higher settling rates) but had no detectable effect on dispersion consolidation. The adsorption of PAM was significantly improved by prior addition of the metal ions. In the presence of Mn(II) or Ca(II) ions, the flocculant adsorption density was enhanced at pH 7.5 for Mn(II) and pH 10.5 for Ca(II). Optimum flocculation conditions, involving partial rather than complete particle surface coverage by both metal ions and flocculant, were identified. As a consequence, the metal ions and flocculant acted synergistically to enhance dewatering, producing particle interactions that were more conducive to high settling rates and greater consolidation of kaolinite dispersions at pH 7.5 than 10.5.     

A Molecular Study of Aspirin and Tenofovir Using Gold/Dextran Nanocomposites and Surface-Enhanced Raman Spectroscopy

In this study, we show how surface enhanced Raman spectroscopy (SERS) can be used to monitor the molecular behaviour of aspirin and tenofovir as a means of screening medication for quality control purposes. Gold-coated slides combined with gold/dextran nanoaggregates were used to provide signal enhancement of the drugs using SERS. Aspirin (10% w/v) and tenofovir (20% v/v) were analysed in the presence of the nanomaterials to determine trends in molecular response to changes in gold/dextran concentrations. Qualitative analysis of the functional groups showed specific trends where the peak area increased with polarizability, electron density and decreased atomic radii. Steric hinderance effects also affected the trends in peak area due to the amount of gold/dextran nanoparticles in solution. Statistical analysis provided accurate and precise linear relationships (R² = 0.99) for the ester and adenine functional groups of aspirin and tenofovir, respectively. From the above findings, the combined use of gold nano-scaffolds and gold/dextran nanomaterials amplified the Raman signal from the drugs to allow for systematic evaluation of their molecular properties. Although more experiments to correlate the findings are still needed, this SERS approach shows great potential as a screening method in the quality control of medications.     

A study of final state deuteron events in 1.825 GeV/c pd interactions

The study of pd → ndπ⁺ and pd → pdπ^O reactions shows that the “slow deuteron” inelastic events are dominated by peripheral processes. Box diagrams are presented for the production mechanism of the 2.2 GeV/c² dπ enhancements. Evidence is presented that for ‘fast deuteron’ events d¹⁺⁺ and d¹⁺ resonances at 2.375 ± 0.010 GeV/c² with a width of 0.075 ± 0.015 GeV/c² are produced via baryon exchange. The elastic events have been compared with Glauber multiple scattering theory with reasonable agreement.     

A new antibacterial benzophenone glycoside from Psidium guajava (Linn.) leaves

Bioactivity-guided fractionation of methanol extract from the leaves of Psidium guajava L. (Myrtaceae) yielded a new benzophenone glycoside, Guajaphenone A (2) together with two known compounds, Garcimangosone D (1) and Guaijaverin (3). Their structures were elucidated by analysis of spectroscopic data including 1D and 2D NMR and electrospray ionisation mass spectrometry (ESI-MS). The isolated compounds were screened against standard strains of Gram-positive and Gram-negative bacteria using broth dilution assay method, and the MIC values determined and compared with reference antibiotic ceftriaxone. They were found to have significant antibacterial activities against Escherichia coli and Staphylococcus aureus with all of them showing better activities against S. aureus, but displaying weaker activities, in comparison to ceftriaxone. However, despite reduced effect of these compounds against the organisms, this work opens the perspective to use these molecules as ‘leads’ for the design of novel and selective drug candidates for some tropical infectious diseases.     

Electrical conductances of aqueous sodium trifluoromethanesulfonate from 0 to 450°C and pressures to 250 MPa

The electrical conductances of dilute (0.001 to 0.1 mol-kg^?1) aqueous sodium trifluoromethanesulfonate (NaCF₃SO₃) solutions have been measured from 0 to 450°C and pressures to 250 MPa. The limiting molar conductance $\Lambda _0 $ increases with increasing temperature from 0 to 300°C and decreasing density from 0.8 to 0.3 g-cm^?3. Above 300°C, $\Lambda _0 $ is nearly temperature independent, but increases linearly with decreasing density. The logarithm of the molal association constant of NaCF₃SO₃ calculated at temperatures from 372 to 450°C is represented as a function of temperature (Kelvin) and density of water (g-cm^?3) by $$\log K_m = 0.888 - 330.4/T - (12.83 - 5349/T)\log \rho _w $$ The relative strengths of NaCF₃SO₃ and NaCl are similar within the accuracy of the current measurements over the limited range of temperature and pressure that could be investigated here.     

Convenient Synthesis of 3-Styrylphthalides

A convenient, high yield, two-step method is described for 3-styrylphthalides (3a - e) from 3-phenacylphthalides (1a - e)     

Negative Ion In-Source Decay Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry for Sequencing Acidic Peptides

Matrix-assisted laser desorption/ionization (MALDI) in-source decay was studied in the negative ion mode on deprotonated peptides to determine its usefulness for obtaining extensive sequence information for acidic peptides. Eight biological acidic peptides, ranging in size from 11 to 33 residues, were studied by negative ion mode ISD (nISD). The matrices 2,5-dihydroxybenzoic acid, 2-aminobenzoic acid, 2-aminobenzamide, 1,5-diaminonaphthalene, 5-amino-1-naphthol, 3-aminoquinoline, and 9-aminoacridine were used with each peptide. Optimal fragmentation was produced with 1,5-diaminonphthalene (DAN), and extensive sequence informative fragmentation was observed for every peptide except hirudin(54–65). Cleavage at the N–Cα bond of the peptide backbone, producing c′ and z′ ions, was dominant for all peptides. Cleavage of the N–Cα bond N-terminal to proline residues was not observed. The formation of c and z ions is also found in electron transfer dissociation (ETD), electron capture dissociation (ECD), and positive ion mode ISD, which are considered to be radical-driven techniques. Oxidized insulin chain A, which has four highly acidic oxidized cysteine residues, had less extensive fragmentation. This peptide also exhibited the only charged localized fragmentation, with more pronounced product ion formation adjacent to the highly acidic residues. In addition, spectra were obtained by positive ion mode ISD for each protonated peptide; more sequence informative fragmentation was observed via nISD for all peptides. Three of the peptides studied had no product ion formation in ISD, but extensive sequence informative fragmentation was found in their nISD spectra. The results of this study indicate that nISD can be used to readily obtain sequence information for acidic peptides.

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Three hydroxylated lupeol-based triterpenoid esters isolated from the Eastern Nigeria mistletoe parasitic on Kola acuminata

Column fractionation and purification of an n-hexane fraction led to the isolation of three lupeol-based triterpenoid esters from the leaves of the Eastern Nigeria mistletoe, Loranthus micranthus Linn parasitic on a local kola nut tree, Kola acuminata. These three compounds were adequately characterised using a combination of UV/visible, IR, NMR (13C-NMR and 1H-NMR), DEPT, MS and two-dimensional correlation (H-H COSY, Hetero-nuclear Single Quantum Correlation (HSQC), HMBC, NOE and NOESY) studies as 7β,15α-dihydroxyl-lup-20(29)-ene-3β-esters of palmitic (I), stearic (II) and eicosanoic acids (III). The characterisation of other isolated compounds is ongoing. Remarkably, this is the first report of the existence of fatty acid esters of an unusual 7β,15α-dihydroxylated lupeol in the Eastern Nigeria mistletoe. These isolated compounds might contribute in part to the numerous established bio-activities of the Eastern Nigeria mistletoes.