A new micro-cell for continuous-flow pulsed voltammetric analysis

The effect of p-toluenesulfonate and trifluoromethanesulfonate supporting electrolytes on the polarographic reduction of some alkaline earth and transition metal ions in N,N-dimethylformamide and acetonitrile has been investigated. Trifluoromethanesulfonate behaved similarly to perchlorate in dimethylformamide, while the half-wave potentials in p-toluenesulfonate supporting electrolyte shift to more negative potentials than those in perchlorate. in acetonitrile, the half-wave potentials shift to more negative potentials in trifluoromethanesulfonate than in perchlorate. The effect of the supporting electrolyte on the shift of the half-wave potential can be explained as the ion-pair formation between the divalent cation to be reduced and the supporting electrolyte anion.     

Liquid-liquid extraction of zinc from aqueous thiocyanate solutions with 5-(-4-pyridyl)nonane in benzene

5-(4-Pyridyl)nonane dissolved in benzene has been applied to the extraction of zinc, down to very low concentration (< 10(-6)M), from aqueous thiocyanate solutions. The metal can be quantitatively extracted from neutral and acidic thiocyanate solutions (up to 5M HCl, 0.25M HNO(3) or 0.25M H(2)SO(4)) in a single extraction. Equilibration times of 5 min are sufficient for almost complete extraction. The optimum thiocyanate concentration range is 0.05-0.5M. Among the common anions chloride exerts a slight depressing effect on extraction from neutral solution when present in high concentration. The extraction mechanism and the composition of the extracted complexes of zinc are discussed. The metal is predominantly extracted by means of a solvate mechanism. The effect of chloride, nitrate, sulphate, acetate, citrate, oxalate and ascorbate ions on the extraction of zinc is described. Several elements, including those of interest in separation of zinc, have been tested for extraction from O.1M KSCN at the optimal concentrations of the mineral acids, and the separation factors estimated.     

Continuous production of butanol from starch-based packing peanuts

Acetone, butanol, ethanol (ABE, or solvents) were produced from starch-based packing peanuts in batch and continuous reactors. In a batch reactor, 18.9 g/L of total ABE was produced from 80 g/L packing peanuts in 110 h of fermentation. The initial and final starch concentrations were 69.6 and 11.1 g/L, respectively. In this fermentation, ABE yield and productivity of 0.32 and 0.17 g/(L·h) were obtained, respectively. Compared to the batch fermentation, continuous fermentation of 40 g/L of starch-based packing peanuts in P2 medium resulted in a maximum solvent production of 8.4 g/L at a dilution rate of 0.033 h⁻¹. This resulted in a productivity of 0.27 g/(L·h). However, the reactor was not stable and fermentation deteriorated with time. Continuous fermentation of 35 g/L of starch solution resulted in a similar performance. These studies were performed in a vertical column reactor using Clostridium beijerinckii BA101 and P2 medium. It is anticipated that prolonged exposure of culture to acrylamide, which is formed during boiling/autoclaving of starch, affects the fermentation negatively.     

In situ DMSO hydration measurements of HTS compound libraries

Compounds used in high throughput screening (HTS) are typically dissolved in DMSO. These solutions are stored automation-friendly racks of wells or tubes. DMSO is hygroscopic and quickly absorbs water from the atmosphere. When present in DMSO compound solutions, water can accelerate degradation and precipitation. Understanding DMSO hydration in an HTS compound library can improve storage and screening methods by managing the impact of water on compound stability. A non-destructive, acoustic method compatible with HTS has been developed to measure water content in DMSO solutions. Performance of this acoustic method was compared with an optical technique and found to be in good agreement. The accuracy and precision of acoustic measurements was shown to be under 3% over the tested range of DMSO solutions (0% to 35% water by volume) and insensitive to the presence of HTS compounds at typical storage concentrations. Time course studies of hydration for wells in 384-well and 1536-well microplates were performed. Well geometry, fluid volume, well position and atmospheric conditions were all factors in hydration rate. High rates of hydration were seen in lower-volume fills, higher-density multi-well plates and when there was a large differential between the humidity of the lab and the water content of the DMSO. For example, a 1536-well microplate filled with 2microL of 100% DMSO exposed for one hour to a laboratory environment with approximately 40% relative humidity will absorb over 6% water by volume. Understanding DMSO hydration rates as well as the ability to reverse library hydration are important steps towards managing stability and availability of compound libraries.     

Distribution studies of metal ions on stannic arsenate in butanol-HNO3 systems: Quantitative separation of Ni−Fe,Ni−Cu,Cd−Hg and Pb−Hg

Summary This paper deals with systematic distribution studies of metal ions on stannic arsenate in butanol-HNO₃ systems. K_d values of metal ions have been determined by the batch process in solvent systems containing varying proportions of butanol and 50% HNO₃. Quantitative binary separations of Ni–Fe, Ni–Cu, Cd–Hg and Pb–Hg have been obtained on the basis of information from the studies.     

Implementation of an All-Optical NOR Gate Using a Multi-Wavelength Injection-Locked Diode Laser

We demonstrated an all optical NOR gate operating at 10 Gb/s using a multi-wavelength mutual injection-locked Fabry-Perot laser diode (FP-LD).     

Coherent control in a single semiconductor quantum dot exhibiting excitonic and biexcitonic features

We have developed a simplified theoretical model to analyze the phenomenon of coherent control in a single semiconductor quantum dot excited by a pair of optical pulses. The first pulse populates a biexciton state by two-photon absorption while the second pulse generates population in the exciton state via deexcitation from the biexciton state. We have used density-matrix analysis for a 3-level system to calculate the time dependent biexciton and exciton state populations. The usual 9×9 matrix has been reduced to a 6×6 matrix. The time variation of the population in each state and it’s dependence on the pulse delay manifest coherent control. Numerical estimates made for In_0.5Ga_0.5As/GaAs single quantum dots qualitatively agree with the recent experimental results. PACS 78.67.Hc; 42.50.Md; 78.55.Cr     

Diphenylamine as an n and π donor in the solid-state reaction of 2,4-dinitrotoluene with diphenylamine

The kinetics and mechanism of the reaction of 2,4-dinitrotoluene with diphenylamine were studied in the solid state. The reaction product is a charge transfer complex with a localized intermolecular interaction as shown by uv and ir spectroscopy. The solid-state studies were complemented by some NMR studies in CCl₄. A novel feature of the study reveals that diphenylamine in this case is a much more powerful n donor than a π donor.     

The tricyanomercurate(II) ion

The tricyanomercurate(II) ion, [Hg(CN)₃]^?, is isolated in the form of its solid caesium salt from a 1:1:1 ethanolic solution of CsF, KCN and Hg(CN)₂, and characterised by IR and Raman vibrational spectroscopy. Assignments are made for the CN and HgC stretching vibrations and the HgCN bending vibrations. The spectra are consistent with the [Hg(CN)₃]^? ion occupying a site of C₁ symmetry.