Temperature effect on peak width and column efficiency in subcritical water chromatography

Subcritical water has been recently employed as the mobile phase to eliminate the use of organic solvents in reversed-phase liquid chromatography. Although the influence of temperature on retention in subcritical water chromatography has been reported, the temperature effect on peak width and column efficiency has not yet been quantitatively studied. In this work, several polar and chlorinated compounds are separated using pure subcritical water on Zorbax RX-C8, PRP-1 (polystyrene-divinylbenzene), Hypersil ODS, and ZirChrom-polybutadiene columns. Isothermal separations are performed at temperatures ranging from 60 degrees C to 160 degrees C. The retention time and peak width of analytes are reduced with increasing temperature. However, the column efficiency is either improved or almost unchanged with the increasing temperature in the low-temperature range (lower than the 100 degrees C to 120 degrees C range), but it is decreased when temperature is further raised in the high-temperature range (higher than the 100 degrees C to 120 degrees C range). Therefore, a maximum in column efficiency is obtained at temperatures within the 100 degrees C to 120 degrees C range in most cases.     

Application of calorimeters for 5 MeV EB and bremsstrahlung dosimetry

Graphite and water calorimeters, which were developed for use a 10 MeV electron beams (EB) at Riso National Laboratory, were used for process validation and routine dosimeter calibration at a 5 MeV EB. Water calorimeters were used for reference measurements for 5 MeV EB, the response was found to be directly proportional to the beam current and the variation among three water calorimeters was less than ± 2 % in the range of 10 to 40 kGy. CTA, PMMA, RCD dosimeters were calibrated by irradiating the dosimeters and water calorimeters simultaneously. The water calorimeters was proved to be an useful tool at 5 MeV EB. Graphite calorimeters gave reproducible readings within 3.3 % relative errors (95% confidence level) for X-ray measurement.     

Binding methyl orange and hydrophobic fluorescent probes by poly(2-dimethylaminoethyl methacrylate) and copolymers of 2-dimethylaminoethyl methacrylate and N-vinyl-2-pyrrolidone: pH dependence of the binding and fluorescence intensity

The pH dependence of the interaction of poly(2-dimethylaminoethyl methacrylate) and copolymers of 2-dimethylaminoethyl methacrylate and N-vinyl-2-pyrrolidone with methyl orange, 2-p-toluidinylnaphthalene-6-sulfonate (TNS), and 1,6-diphenyl-1,3,5-hexatriene (DHT) was studied by equilibrium dialysis and fluorescence measurements at pH's 7–10. The first binding constant accompanying the binding of methyl orange and TNS by the polymers, in particular the homopolymer, shows a maximum around pH 8 and maximal fluorescence intensity of TNS is obtained around pH 8.5 in the presence of the polymers. To elucidate these observations the pH-induced conformational changes of the homopolymer were examined by potentiometric titration and viscosity measurements and the thermodynamic parameters that accompany the binding were calculated. The polymer was found to change from an extended coil at lower pH to a compact coil at higher pH. The electrostatic attraction between the sulfonate group of the small molecule and the protonated nitrogen atoms on the polymer is increased at lower pH and the hydrophobic interaction between the hydrophobic moieties of the polymer and the small molecule is enhanced at higher pH. The results obtained for the dye binding and fluorescence intensity were discussed in terms of the electrostatic and hydrophobic interactions.     

Thermal decomposition of basic copper carbonate,CuCO3 · Cu(OH)2 · H2O,in carbon dioxide atmosphere (0–50 atm)

The thermal decomposition of basic copper carbonate, CuCO₃ · Cu(OH)₂ · H₂O, was studied by high-pressure DTA under high-pressure carbon dioxide (0–50 atm).The DTA-TG measurement in air showed that the peak temperature was influenced more by heating rate than by sample weight.Decomposition via dehydration and decarbonation was rapidly finished in a single step, and no intermediate was found. The decomposition temperature was strongly influenced by the partial pressure of carbon dioxide. The decomposition temperature increased in the range 0 atm < _Pco2 < 7 atm, but was nearly constant above P_co2 = 7 atm. Explaining these phenomena was approached by various considerations.     

Comparative study of electron transfer reactions at the ionic liquid/water and organic/water interfaces

The rates of electron transfer (ET) reactions at the water/ionic liquid (IL) interface have been measured for the first time using scanning electrochemical microscopy. The standard bimolecular rate constant of the interfacial ET between ferrocene dissolved in 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and aqueous ferricyanide (0.4 M-1 cm s-1) was found to be approximately 30 times higher than the corresponding rate constant measured at the water/1,2-dichloroethane interface. The driving force dependence of the ET rate was investigated over a wide range of the interfacial potential drop values (>200 mV). The observed Butler-Volmer-type dependence is discussed in terms of the interfacial model. The ET was also probed at the interface between aqueous solution and the mixture of the IL and 1,2-dichloroethane. The mole fractions in this mixture were varied systematically to investigate the transition from the water/organic to the water/IL interface. The observed decrease in the rate constant with increasing mole fraction of 1,2-dichloroethane is in contrast with the previously reported direct correlation between the electrochemical rate constant and the diffusion coefficient of redox species in solution.     

Interaction of crosslinked polyvinylpyrrolidone with a homologous series of methyl orange derivatives in aqueous and nonaqueous solutions: Thermodynamics of the binding equilibria

The extent of binding of methvI orange, ethyl orange, propyl orange, and butyl orange by crosslinked polyvinylpyrrolidone was measured in all aqueous Solution. The first binding constants and the thermodynamic parameters accompanying the binding were evaluated. These values were compared with those of water-soluble polyvinylpyrrolidone. The first binding constant, the absolute magnitude of ΔF°, and the value of ΔS° of the crosslinked polyvinylpyrrolidone are substantially larger than those of the water-soluble product for any particular dye. These behaviors can be accounted for in terms of increased hydrophobic domains in the former and enhanced hydrophobic contribution in the binding process. Also the binding of the dye by the crosslinked polymer in a nonaqueous solvent, ethylene glycol, was measured to assess the contribution of hydrophobic interaction to the dye-polymer complex formation in aqueous medium. It was found that the binding of butyl orange by the crosslinked polymer is suppressed in ethylene glycol and the contribution of entropy term to the free energy change in the aqueous environment is large compared with that in ethylene glycol. The significance of the hydrophobic of the hydrophobic interaction in the dye-polymer association process is described.     

A study of the formation of LiNbO3 in the system Li2CO3Nb2O5

The formation process of LiNbO₃ in the system Li₂CO₃Nb₂O₅ was discussed from the results of non-isothermal or isothermal TG experiments and X-ray analysis. The mixture Li₂CO₃ and Nb₂O₅ in mole ratios of 1:3, 1:1 or 3:1 was heated at a rate of 5°C min^?1 or at various temperatures fixed in the range 475 to 677°C. If the system has a composition of Li₂CO₃ + 3Nb₂O₅ or 3Li₂CO₃ + Nb₂O₅, the reaction between Li₂CO₃ and Nb₂O₅ proceeds with CO₂ evolution to form LiNbO₃ at ca. 300–600°C, but Nb₂O₅ or Li₂CO₃ remains unreacted. A composition of Li₂CO₃ + Nb₂O₅ gives LiNbO₃ at 300–700°C. The diffusion of Li₂O through the layer of LiNbO₃ is rate-controlling with an activation energy of 51 kcal mol^?1. The reaction between LiNbO₃ and Nb₂O₅ gives LiNb₃O₈ at 600–700°C. At 700–800°C, a slight formation of Li₃NbO₄ occurs by the reaction between LiNbO₃ and Li₂O at the outer surface of LiNbO₃ and the Li₂O component of Li₃NbO₄ diffuses toward the boundary of the LiNb₃O₈ layer through the LiNbO₃ layer. The single phase of LiNbO₃ is formed above 850°C.     

Substoichiometric and non-destructive determination of trace impurities in high-purity optical glasses by neutron activation analysis

A method of radioactivation analysis has been developed for the determination of 17 elements as impurities in high-purity optical glasses. The substoichiometric extraction of platinum with dithizone was studied and a simple procedure was proposed for the determination of platinum. Copper and manganese were also determined substoichiometrically by the extractions with dithizone and with thenoyltrifluoracetone, respectively. The non-destructive γ-ray spectrometry using a Ge(Li) detector has been applied for the determination of the other 14 elements (Ag, Co, Cr, Eu, Fe, Ir, Sc, Zn, Cs, Hf, Rb, Sb, Ta and Tb). Impurity elements at the ppb level were analysed by the proposed method and it is shown that the method is reliable for the determination of trace impurities in high-purity optical glasses.     

Binding of anthraquinone dyes by polyion complexes consisting of a piperidinium cationic polymer and various polyanions in aqueous solution

The extent of binding of 1-amino-4-alkylaminoanthraquinone-2-sulfonates (alkyl?methyl, ethyl, propyl, and butyl), which have different chemical structures from methyl orange derivatives, by polyion complexes consisting of a piperidinium cationic polymer and various polyanions such as sodium poly acrylate, poly methacrylate, poly styrenesulfonate, carboxymethylcellulose, and dextran sulfate, was measured in an aqueous solution. The effect of alkyl group of the anthraquinone dye on the binding behavior was investigated. Also, the resultant binding characteristics were compared with those previously observed with methyl orange and its homologs. These polyion complexes exhibited very strong binding affinity toward the anthraquinone dye. The polyion complex of the polycation and sodium poly styrenesulfonate bound the dye noncooperatively and the binding process was athermal. The first binding constant accompanying the binding is of the order of 10⁵–10⁶. In contrast, the polyion complexes composed of the polycation and the other polyanions exhibited strong cooperative binding and the binding process was exothermic. The possible mode of binding is discussed.     

Prostaglandin chemistry—VIII : Synthesis of optically active 7-oxoprostaglandins

Regiospecific α-acylation of β-alkenylated enolates generated by conjugate addition of lithium organocuprates to α,β-unsaturated ketones is described. Several new 7-oxoprostaglandin analogues, 7-oxoprostaglandin E₁ (18), 11-deoxy-7-oxoprostaglandin E₁ (23), and their 15-epi enantiomers 17 and 22, were synthesized by conjugate addition-acylation method. From optically active 4(R) -t - butyldimethylsiloxycyclopent - 2 - en - 1 - one (R-11), 7-oxoprostaglandin E₁ (18) was synthesized. Determination of the absolute configuration of 11-deoxy-7-oxoprostaglandin E₁ (23) and its 15-epi enantiomer (22) on the basis of CD study is described. Successful acylation of β-alkenylated lithium copper enolates with reactive acylating agents such as thiol esters and N-acyl imidazole as well as acyl halides is described.