The Liquid Junction Potential in Potentiometric Titrations. X. The Calculation of Potentials Across Liquid Junctions of the Type AY|AY+HY+BYz(B)+AyL for Emf Cells Where Strong or Weak Complexes are Formed at Constant Ionic Strength and −log10[H+]≤7

Equations are derived for the calculation of the total potential anomalies in Emf cells with liquid junctions (ΔE _J ) in mV and at 25.0 °C, defined as

Improvement of pesticide adsorption capacity of cellulose fibre by high-energy irradiation-initiated grafting of glycidyl methacrylate

Cellulose as a renewable raw material was used for preparation of adsorbent of organic impurities in wastewater treatment. Hydrophobic surface of cellulose substrate was developed by grafting glycidyl methacrylate in simultaneous grafting using gamma irradiation initiation. Water uptake of cellulose significantly decreased while adsorption of phenol and a pesticide molecule (2,4-dichlorophenoxyacetic acid: 2,4-D) increased upon grafting. Adsorption equilibrium data fitted the Freundlich isotherm for both solutes.     

A thermoanalytical assessment of an organoclay

High resolution thermogravimetric analysis (TG) has attracted much attention in the synthesis of organoclays and its applications. In this study, organoclays were synthesised through ion exchange of a single cationic surfactant for sodium ions, and characterised by methods including X-ray diffraction (XRD) and TG. The changes of surface properties in montmorillonite (MMT) and organoclays intercalated with surfactant were determined using XRD through the changes in the basal spacing. The TG was applied in this study to investigate more information of the configuration and structural changes in the organoclays with thermal decomposition. There are four different decompositions steps in differential thermogravimetric curves. The obtained TG steps are relevant to the arrangement of the surfactant molecules intercalated in MMT and the thermal analysis indicates the thermal stability of surfactant modified clays. This investigation provides new insights into the properties of organoclays and is important in the synthesis and processing of organoclays for environmental applications.     

Aminosilane-based functionalization of two-photon polymerized 3D SU-8 microstructures

There is an increasing interest in functionalized complex 3D microstructures with sub-micrometer features for micro- and nanotechnology applications in biology. Depending primarily on the material of the structures various methods exist to create functional layers of simple chemical groups, biological macromolecules or metal nanoparticles. Here an effective coating method is demonstrated and evaluated on SU-8 based 3D microstructures made by two-photon polymerization. Protein streptavidin and gold nanoparticles (NP) were bound to the microstructures utilizing acid treatment-mediated silane chemistry. The protein surface density, quantified with single molecule fluorescence microscopy revealed that the protein forms a third of a monolayer on the two-photon polymerized structures. The surface coverage of the gold NPs on the microstructures was simply controlled with a single parameter. The possible degrading effect of the acid treatment on the sub-micrometer features of the TPP microstructures was analyzed. Our results show that the silane chemistry-based method, used earlier for the functionalization of large-area surfaces can effectively be adapted to coat two-photon polymerized SU-8 microstructures with sub-micrometer features.     

Cobalt Carbonate as an Electrocatalyst for Water Oxidation

Co^II salts in the presence of HCO₃⁻/CO₃²⁻ in aqueous solutions act as electrocatalysts for water oxidation. It comprises of several key steps: (i) A relatively small wave at E_pa≈0.71 V (vs. Ag/AgCl) owing to the Co^III/II redox couple. (ii) A second wave is observed at E_pa≈1.10 V with a considerably larger current. In which the Co^III undergoes oxidation to form a Co^IV species. The large current is attributed to catalytic oxidation of HCO₃⁻/CO₃²⁻ to HCO₄⁻. (iii) A process with very large currents at >1.2 V owing to the formation of Co^V(CO₃)₃⁻, which oxidizes both water and HCO₃⁻/CO₃²⁻. These processes depend on [Co^II], [NaHCO₃], and pH. Chronoamperometry at 1.3 V gives a green deposit. It acts as a heterogeneous catalyst for water oxidation. DFT calculations point out that Coⁿ(CO₃)₃ⁿ⁻⁶, n=4, 5 are attainable at potentials similar to those experimentally observed.     

The Liquid Junction Potential in Potentiometric Titrations. VIII. EMF Titrations Proposed for the Determination of Certain Transport Numbers

Some useful emf titrations, for cells with large liquid junction potentials are proposed for the determination of the transport numbers of strong electrolytes of the following types: (1) Strong electrolytes A_yH_uL or A_yL (used as a complexing agent) with the absolute values for the anionic charges y = 1, 2 or 3. The pK _a values of the corresponding acid H_yL must be well separated. The method was tested in sodium hydrogen ascorbate solutions. (2) Pure electrolyte BY_z(B), where the cation B^z(B)+ can form an amalgam. (3) Metal perchlorates.     

Study of the interaction of structurally similar bioactive compounds by thin-layer chromatography

The interaction between steroids and cholesterol is studied by reversed-phase thin-layer chromatography (TLC) using TLC plates impregnated by cholesterol and methanol-water mixtures as the eluents. The R(M) values obtained are in linear correlation with the methanol concentration of the eluent. The slope obtained from the linear regression analysis, which is characteristic of the strength of interaction, is determined. Stepwise regression and principal component analysis are carried out to find a relationship between the physicochemical parameters of steroid drugs and the strength of the interaction, which is followed by nonlinear mapping and cluster analysis to visualize the obtained results. The results show that steric and electronic parameters of the steroid drugs have a significant effect on the strength of the interaction between these structurally similar molecules.     

Ring transformations of 1,3-benzothiazine derivatives II conversion of 6α-aryl-7α-chloro-2,3(2′,3′-dialkqxybenzo)-1-thiaoctems3 into 2-carbomethoxy-3-aryl-7,8-dialkoxy-4.5-dihydro-1,4-benzothiazepines

6,7-Dialkoxy-2-aryl-4$\text{H}$1-1,3-benzothiazines (1a?) react with chloroacetyl chlorlde to give condensed β-lactam derivatives (2a?). Basic treatment of 2a? in methanol led to the corresponding 1,4-banzothiazepine derivativee (3a?) $\text{via}$ring expansion. The structures of the products were determined by IR, NMR and MS studies     

Preparation,characterization, and application of a novel immobilized carboxypeptidase B

Pig pancreas carboxypeptidase B has been immobilized by covalent attachment to a polyacrylamide-type bead support possessing carboxylic functional groups activated by water-soluble carbodiimide. The optimum conditions of immobilization were determined. The activation of the support and the coupling reaction were performed in 0.1 M sodium citrate/sodium phosphate buffer (pH 4.5) using a support-carbodiimide-enzyme weight ratio 4:8:1 at 0-4 degrees C. Under such conditions, the highest activity achieved was 6700 U/g solid. The catalytic properties and stability of immobilized carboxypeptidase B were studied and compared with the corresponding properties of the soluble enzyme. The specific activity of the immobilized enzyme calculated on bound protein basis was about 70% of that of soluble enzyme. The optimum pH for the catalytic activity of the immobilized carboxypeptidase B was practically identical with that of soluble enzyme (pH 7.6-7.7). The apparent optimum temperature of the immobilized carboxypeptidase B was about 7 degrees C higher than that of the soluble enzyme. With hippuryl-L-arginine as substrate, Kmapp value of the immobilized enzyme was tenfold higher than the Km value of the soluble enzyme. The conformational stability of the enzyme was markedly enhanced by the strongly hydrophylic microenvironment in a wide temperature and pH range. The immobilized carboxypeptidase B was used for stepwise digestion of cytochrome C.     

TLC and GC Analysis of the Essential Oils of Stachys Species

JPC – Journal of Planar Chromatography – Modern TLC - Species of the Lamioideae subfamily of the family Lamiaceae, including Stachys species, do not contain much essential oil. The...