十二烷基磺酸钠增敏电化学法超灵敏地测定尿液中拓扑替康盐酸盐

提出了在一次性电极(改进的石墨浸蜡电极)上,利用十二烷基磺酸钠增敏电化学法亚皮摩尔级测定拓扑替康盐酸盐的方法.考察了不同种类的表面活性剂对拓扑替康盐酸盐的电化学响应.结果表明,十二烷基磺酸钠能够显著地提高其电化学响应.在优化的实验条件下,氧化峰电流跟拓扑替康盐酸盐浓度的对数在2.0×10-12至1.0×10-11mol/L和8.0×10-11至8.0×10-10mol/L范围内成线性关系,检出限为6.4×10-13mol/L.该方法用于检测尿液中的拓扑替康盐酸盐.     

A review on enzyme and ultrasound: A controversial but fruitful relationship

A critical review on the effect of ultrasound (US) on enzymes and their biocatalytic action is presented here. Discussion on the information users of US acquire before utilizing the different devices, and the importance they give to US frequency is constant along the review. The authors have gone into the different areas in which the US–enzyme binomial has been applied. The lack of enough information on the US–enzyme-working conditions under which each piece of research has been developed, and the necessity to provide complete information on the data and metadata to give enough light on each piece of research (and thus on the potential comparison of results from different studies) are critically exposed. With this aim, the study has been divided into the positive effect of US on enzymes to favor the production of metabolites, polymers or proteins; and the degradation, inhibition or activation of the biocatalyst under US application. Also the effect of US on enzyme production and the main fields of application of the US–enzyme binomial are discussed.     

Size-controlled synthesis of SnO2 nanoparticles using reverse microemulsion method

Tin oxide nanoparticles were prepared using an ionic surfactant (sodium dodecyl sulfate) and tin (IV) chloride as an inorganic precursor via the reverse microemulsion method. The size of the nanoparticles is controlled by variation of water-to-surfactant ratio. Eliminating of surfactant in prepared nanoparticles was confirmed by the infrared spectroscopy after sequential calcinations. Transmission electron microscopy, surface area, pore volume, average pore diameter, pore size distribution and X-ray diffraction results were used for evaluation of size distribution, shape and structure of prepared SnO₂ nanoparticles. Transmission electron micrographs confirmed that the obtained materials are spherical nanoparticles. The X-ray diffraction results show the crystalline phases of all samples are SnO₂ with tetragonal structured crystal. In addition, the X-ray diffraction and transmission electron microscopy data showed that the size of SnO₂ nanoparticles decreased with decreasing the water-to-surfactant ratio.     

pH Induced Partitioning and Interactions of Ciprofloxacin Hydrochloride with Anionic Surfactant Sodium Dodecyl Sulfate Using Ultraviolet and Fourier Transformed Infrared Spectroscopy Study

Ultraviolet (UV) and Fourier transformed infrared (FTIR) spectra of ciprofloxacin hydrochloride (Cpf) were studied under different pH conditions. The effect of aqueous, strong acidic, (pH 0.5–1.0) and a basic (pH 9.2) conditions on spectral behavior of Cpf was investigated in aqueous as well as in micellar environment of sodium dodecyl sulfate (SDS). Cpf shows partitioning from aqueous to micellar phase in a strong acidic as well as in a basic environment. Cpf shows no partitioning or binding to micelle in aqueous phase. Conductivity studies show that critical micelle concentration of SDS is increased with increasing concentration of Cpf. Different sites are responsible for binding under different pH conditions.     

Use of a Dynamic Light Scattering Technique for SDS/Water/Pentanol Studies

The interpretation of micelle/aggregate size obtained by use of the DLS technique for SDS/water/pentanol systems was discussed by comparison of the results of measurement with theoretical data. For most of the studied systems, the apparent radii (R _h,app ) did not satisfactorily characterize the size of the aggregates (R _h,app  < 1 nm). The use of a correction factor (f = 0.26) confirmed that the discrepancies were associated with the electrostatic intermicellar interactions. However, the fuzzy optical interface between dispersed and dispersing phases can also be the reason of such results. An increase of pentanol content caused a decrease of the droplet radius in w/o systems but in o/w systems the changes were negligible.     

Effect of Surfactant Addition on the Structure of Silver Aggregates Produced by Galvanic Cell Reaction and Fabrication of Superhydrophobic Surfaces

The effect of cationic or anionic surfactant on the structure of the silver particles produced by galvanic cell reaction is studied. In the absence of any surfactant, both spherical and spindle-like Ag particles are produced, which exhibit binary structures with both micro- and nanoscale characteristics. Addition of cationic surfactant cetyltrimethylammonium bromide (CTAB) in the reaction solution results in the formation of spherical Ag particles with much smaller sizes. While anionic surfactant sodium dodecyl sulfate (SDS) results in the spindle-like Ag particles. Moreover, the rough Ag surfaces can be easily fabricated by direct deposition of the Ag aggregates onto the silicon surface from solution. After further chemisorption of a self-assembled monolayer of n-dodecanethiol, the Ag aggregates exhibit superhydrophobic properties.     

The Kinetics and Mechanism of Ligand Substitution Reaction of Aquapentacyanoruthenate(II) with Nitroso-R-salt and α-Nitroso-β-Naphthol in Presence of Anionic Surfactant Micelle

The kinetics and mechanism of ligand substitution reaction of coordinated water in complex, [Ru(CN)₅H₂O]^3? by two incoming naphthalene substituted ligands [Lⁿ], that is, Lⁿ = nitroso-R-salt (NRS) and α-nitroso-β-naphthol (αNβN) have been studied spectrophotometrically by following an increase in absorbance at λ_max = 525 nm in aqueous medium in presence of anionic surfactant micelle, sodium dodecyl sulphate (SDS) at 25.0 ± 0.1°C as a function of pH, [nitro-R-salt], [α-nitroso-β-naphthol], [Ru(CN)₅H₂O^3?], [SDS] and ionic strength(I) under pseudo-first-order conditions by taking excess [L]. The values of pseudo-first-order rate constants (k_obs) were evaluated from the slope of ln(A_∞ ? A_t) versus time plots for each variation. Both systems were found to follow a dissociative mechanism (D), through the formation of an intermediate, [Ru(CN)₅]^3?. The activation parameters, that is, enthalpy of activation (ΔH^≠) and entropy of activation (ΔS^≠) were computed from the slope and intercept of ln(k_f/T) versus (1/T) plot, which support the proposed mechanistic scheme.     

Interfacial and Thermodynamic Properties of Formation of Water‐in‐Oil Microemulsions with Surfactants (SDS and CTAB) and Cosurfactants (n‐Alkanols C5–C9)

The interfacial and thermodynamic properties of water‐in‐oil microemulsion systems consisting of water, isopropyl myristate, n‐alkanol, and surfactant have been investigated using the method of dilution. The surfactants used were hexadecyl trimethylammonium bromide and sodium dodecylsulfate, and the cosurfactants were n‐alkanols with varying chain length from (C₅–C₉). The distribution of cosurfactant (n‐alkanol) between the interface of water and oil regions at the threshold level of stability as well as the energetics of the transfer of the cosurfactant from the oil to the interfacial region have been examined as a function of varying cosurfactant chain length (C₄–C₉) and temperature. The structural parameters (including dimension, population density and effective water pool radius) of the dispersed water droplets in the oil phase have also been evaluated and correlated with alkanol chain length.     

Mild,Efficient, and Greener Dethioacetalization Protocol Using 30% Hydrogen Peroxide in Catalytic Combination with Ammonium Iodide

A simple, mild, efficient, and expedient greener dethioacetalization protocol employing a catalytic amount of nontoxic ammonium iodide (10 mol%) in combination with 30% hydrogen peroxide as terminal oxidizer is revealed. The reagent accomplished facile deprotection of 1,3-dithianes and dithiolanes of activated aromatic substrates in an aqueous medium in the presence of sodium dodecylsulfate (SDS) at room temperature under virtually neutral conditions. Deactivated and sterically encumbered substrates, which are otherwise reluctant to cleave under aqueous micellar conditions, were expeditiously cleaved in good to excellent yields in acetic acid. The method is tolerant, with several acid-sensitive protecting groups, such as tert-butyldiphenylsilyl (TBDPS) ether, aryl acetate, NHBoc, and NHBn, and with further oxidation of oxidation-prone activated benzaldehydes and furyl aldehydes. A tentative mechanism of hypoiodous acid–mediated catalytic cleavage is proposed.

Kinetics and Mechanism Studies on Dispersion of CNT in SDS Aqueous Solutions

The objects of this research are to study the dispersion of CNT (carbon nanotube) in SDS (sodium dodecyl sulfate) aqueous solutions with kinetics approach and to obtain some information about mechanism for this dispersion. Firstly, I measured the UV‐visible absorption at 260 nm of CNT in SDS aqueous solutions after different time of dispersion for different concentrations of CNT and SDS. Then, curves of the time‐dependent absorbance were analyzed by various mathematical models and were found to fit well with equation of A = A∞ exp(‐k_obs t), where A∞ is the absorbance at infinite time and k_obs is the observed rate constant. The values of A∞, k_obs, and, minimum time for dispersion can be obtained. From the effects of concentrations of SDS and CNT on A∞ and k_obs, the dissociation constant for CNT‐SDS complex and the optimum ratio of [CNT]/[SDS] can be estimated. Finally, the mechanism for this dispersion may be proposed as” where b‐CNT, CNT, CNT‐SDS, and, k_i s are bounded CNT, exfoliated CNT, CNT‐SDS complex, and, the rate constants, respectively. In this mechanism, b‐CNT is firstly unbounded by supersonic energy to form CNT intermediate with rate constant of k₁, which is proportional to the supersonic energy per time. The CNT intermediate then recombines to form b‐CNT with rate constant k_?1[CNT] or reacts with SDS to form CNT‐SDS complex, which has absorbance at 260 nm in UV‐visible spectrum, with rate constant of k₂ [SDS]. Details of kinetics and mechanism will be discussed in this paper.