Construction of a liquid-membrane type periodate ion-selective electrode and its application to the potentiometric titration of alpha-diols and alpha-amino-alcohols

The construction of a liquid-membrane type periodate ion-selective electrode and its application to the potentiometric titration of alpha-diols and alpha-amino-alcohols are described. The ion-pair of periodate anion with Capriquat (tri-n-octylmethylammonium chloride), is easily extracted into nitrobenzene, and this extract is employed as a liquid ion-exchange membrane. The calibration curve shows Nernstian response towards periodate ion over the concentration range from 10(-1)M to 10(-7)M with a slope of 60 mV/pIO(-)(4). Selectivity coefficients with respect to various ions were evaluated. The electrode potential was independent of pH in the range 2.5-7.5. Some alpha-diols and monoethanolamine were successfully titrated potentiometrically with the aid of the present electrode.     

Valency states of radioactive antimony in hydrochloric acid solutions. Preparation and stability of antimony tracer for radioanalytical use

Variations of¹²⁵Sb valency states in HCl solutions were investigated by the use of the N-benzoyl-N-phenyl-hydroxylamine (BPHA) extraction method.¹²⁵Sb(V) is completely reduced to Sb(III) by one hour refluxing in conc. HCl.¹²⁵Sb(III) is gradually oxidized to Sb(V) in solutions of low HCl concentrations by the effects of their own radiations. Natural light promotes such oxidation reactions. By utilizing such oxidation-reduction effects¹²⁵Sb(V) can be easily prepared from¹²⁵Sb(III) and also¹²⁵Sb(III) can be prepared by the reduction of Cl _aq ⁻ . Their valency states were stable on keeping them in brown-colored bottles at 6M HCl concentrations.     

Photodestruction of fluorophores and optimum conditions for trace DNA detection by automated DNA sequencer.

Although automated DNA sequencers are becoming popular, their sensitivity in detecting DNA bands is still around 10(-17) mole/band. The sensitivity of a system depends on the laser power, labeling fluorophore, and the fluorescence-collecting yield. The emission and photodestruction cross-sections of the fluorophores are critical in optimizing the irradiated laser power and the migration speeds of DNA fragments to achieve high sensitivity. We investigated photodestruction cross-sections of various fluorophores to optimize the irradiation laser power. In addition, we used a cylindrical lens system to improve the fluorescence-collecting yield of a DNA sequencer using side entry laser irradiation. Fluoresceine isothiocyanate (FITC) commonly used in fluorescence studies, is very photo-destructive, the cross-section of the destruction being about 3.8 x 10(-20) cm2 in buffer solution while that of Texas Red is 1.5 x 10(-21) cm2. When the time for DNA fragments to transit through the irradiated region is 11 s, the optimum laser powers are 0.9 mW, with an Ar laser (488 nm) for FITC-DNA, and 18 mW, with an He-Ne laser (594 nm) for Texas Red DNA. We have developed a DNA sequencer, with a cylindrical lens system which improves the fluorescence-collecting efficiency by a factor of 4, and an He-Ne laser (5 mW). Although the sequencer uses a slab gel, an ultra-high sensitivity of 5 x 10(-20) mole/band (S/N-4) was achieved under optimized conditions.     

A comparison of the adsorption of saliva proteins and some typical proteins onto the surface of hydroxyapatite

Adsorption of protein from saliva on hydroxyapatite was compared with adsorption of several typical proteins with different electric charges, i.e. lysozyme, human serum albumin, β-lactoglobulin and ovalbumin. Adsorbed amounts of these proteins were determined and electrophoretic mobilities of protein-covered hydroxyapatite particles were measured, at different values for the adsorbed mass and, therefore, at various degrees of surface coverage. Also, adsorption kinetics were investigated by streaming potential measurements of a hydroxyapatite surface in contact with a protein solution, allowing monitoring of changes in the zeta-potential of the protein-covered hydroxyapatite surface in real time. The adsorbed amounts show that, as compared to most of the other proteins, the saliva proteins have remarkably low adsorption affinity. The measured values for the electrophoretic mobilities indicate that the positively charged proteins in the saliva mixture preferentially adsorb onto the negatively charged hydroxyapatite surface; this is most pronounced at low protein concentration in solution (i.e. at low coverage of the surface by the protein). Preferential uptake of the positively charged saliva proteins during the initial stages of the adsorption process is also concluded from the results of the kinetics experiments. Preferential adsorption of positive proteins is somewhat suppressed by the presence of Ca²⁺ ions in the medium. The results suggest that an acquired pellicle on a tooth in an oral environment contains a significant fraction of positively charged proteins. The positively charged proteins in the pellicle reduce the zeta-potential at the tooth surface to low values; consequently, electrostatic forces are expected to play only a minor role in the interaction with other components (e.g. bacterial cells).     

Anodic a.c. polarography of methylthymol blue

The anodic a.c. polarographic properties of methylthymol blue (MTB) were investigated in the supporting electrolyte of potassium nitrate containing buffer. The difference in the peak potentials of MTB and EDTA is a good measure of the difference in the stabilities of both chelates. The stability constant of mercury(II)-MTB complex was successfully determined on the basis of that reported for the mercury(II)-EDTA complex.     

Non-steady state solidification of the Nd-123 superconducting oxides

Crystal growth of the melt-textured bulk Nd_1+xBa_2−xCu₃O_6+d (Nd123) superconducting oxides was investigated by employing isothermal undercooling solidification with hot-seeding in air. From the relationship between growth length and holding time, the Nd123 crystal was found to have almost stopped growing after a certain growth period, while the growth length increased proportionally to the holding time at an early stage of the crystal growth. As a result of quantitative analysis for the Nd123 crystal of which solidification was terminated, the distribution of the Nd/Ba substitution was observed to decrease in the Nd123 single crystal matrix from the seed crystal to the edge of the Nd123 crystals. Also, the substitution content at the edge of the Nd123 crystal, which corresponds to that at the final stage of the crystal growth, was found to be in good agreement with the minimum substitution of the Nd123 solid solution phase in the equilibrium phase diagram at this process temperature. These compositional changes could be explained using the equilibrium phase diagram as associated with the solid solution formation, which is responsible for the non-steady state solidification of the Nd123 crystals even for the isothermal undercooling processing.     

Critical current density and vortex dynamics in uranium irradiated Co-doped BaFe2As2

We report the effect of defects introduced by heavy-ion irradiation with 2.6 GeV uranium ions at several matching fields in single crystalline Ba(Fe_0.925Co_0.075)₂As₂. The suppression rate of T_c at lower matching fields is larger than that at higher matching fields. The critical current density calculated from magnetic hysteresis loop is enhanced up to 4.1 × 10⁶ A/cm² at 2 K. Clear dips in magnetic hysteresis loops near zero field are observed at high matching fields. Field dependence of normalized relaxation rate is suppressed, and the relationship between the dip and the relaxation rate is discussed.     

Differential pulse-polarographic determination of organotin compounds coated on fishing nets

Summary The pulse-polarographic behaviour of tributyltin chloride (TBTC) and dibutyltin dichloride (DBTC) in ethanol-water mixtures has been studied. The effects of temperature, pH, modulation amplitude, solvent and supporting electrolyte compositions were investigated. The reduction processes are complicated and pH-dependent. DBTC gave one reversible reduction wave and TBTC showed a quasi-reversible one and also several irreversible waves. Both the organotin compounds in the concentration of 10^–7 mol/l were determined by differential pulse polarography. The method was successfully applied to the analysis of commercially available fishing nets. Detection limits were 2.2×10^–7 and 6.2×10^–8 mol/l for TBTC and DBTC, respectively.

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Differential-puls-polarographische Bestimmung von Organozinnverbindungen auf Fischernetzen

Zusammenfassung Das puls-polarographische Verhalten von Tributylzinnchlorid (TBTC) und Dibutylzinndichlorid (DBTC) in Ethanol-Wasser-Gemischen wurde untersucht und die Wirkung von Temperatur, pH, Modulationsamplitude sowie Zusammensetzung des Lösungsmittels und Leitelektrolyts geprüft. Die Reduktionsprozesse waren kompliziert und abhÄngig vom pH. DBTC ergab eine reversible Reduktionswelle, TBTC eine quasireversible Welle, sowie daneben einige irreversible Wellen. Beide Organozinnverbindungen konnten in einer Konzentration von 10^–7 mol/l durch Differential-Puls-Polarographie bestimmt werden. Die Methode wurde erfolgreich auf die Analyse von handelsüblichen Fischernetzen angewandt. Die Nachweisgrenzen lagen bei 2,2·10^–7 (TBTC) bzw. 6,2 · 10^–8 mol/l (DBTC).

This work was supported in part by a Grant-in-Aid for Scientific Research No. 554164 from the Ministry of Education. The authors wish to thank Mr. Y. Komatsu, Clean Kagaku Co., Tokyo, who offered the fishing net samples.