KCl Solution (kcl + solution)

Distribution by Scientific Domains

Selected Abstracts

Flow Injection Analysis of Sulfide Using a Cinder/Tetracyano Nikelate Modified Screen-Printed Electrode

Jyh-Myng Zen
Abstract Flow injection analysis (FIA) of sulfide is presented using a screen-printed carbon electrode modified with a cinder/tetracyano nickelate hybrid (designated as cinder/NiTcSPE). Hybridization of NiTc was achieved in iron-enriched industrial waste cinder material through the bimetallic formation of FeIII[NiII(CN)4]. The electrocatalytic oxidation of sulfide is mediated by the higher oxidation state of Ni in this hybrid-bimetallic complex. The system shows a detection limit (S/N=3) of 0.06,,M and a linear working range up to 1,mM in pH,10, 0.1,M KCl solution. Taking into account the relatively low volatility of the analyte in alkaline conditions, the system is ideally suited for the accurate detection of sulfide. The response of the electrode to sulfide is highly reproducible, thereby offering the potential development of a disposable amperometric sensor for sulfide. Selective detection of sulfide in cigarette smoke is presented in this study as an example of a real sample application. [source]

Microwave Activation of Electrochemical Processes at Glassy Carbon and Boron-Doped Diamond Electrodes

Kumar Sur, Ujjal
Abstract Voltammetric experiments under intense microwave field conditions have been carried out at a carbon microfiber electrode, an array of carbon microfiber electrodes, and at a boron-doped diamond electrode. For the reversible one electron redox systems Fe(CN) and Ru(NH3) in aqueous KCl solution increased currents (up to 16 fold at a 33,,m diameter carbon microelectrode) and superheating (up to ca. 400,K at all types of electrodes) are observed. Electrodes with smaller diameter allow better signal enhancements to be achieved. From the missing effect of the supporting electrolyte concentration on the microwave enhanced currents, it can be concluded that effects observed at carbon electrodes (microwave absorbers) are due to the interaction of microwaves with the electrode material whereas for metal electrodes (microwave conductors) effects are dominated by the interaction of the microwaves with the aqueous dielectric. Short heat pulses can be applied by pulsing the microwave field and relatively fast temperature transients are observed for small electrodes. For the irreversible two electron oxidation of L -dopa in aqueous phosphate buffer, different types of effects are observed at glassy carbon and at boron-doped diamond. Arrays of carbon microfibers give the most reproducible and analytically useful current signal enhancements in the presence of microwaves. [source]

Ammonia exchange on clinoptilolite from mineral deposits located in Mexico

Roberto Leyva-Ramos
Abstract This work investigated the ion exchange of ammonia on clinoptilolite obtained from mineral deposits located in San Luis Potosi and Sonora, Mexico. Experimental ion exchange isotherm data were obtained in a batch adsorber. The effects of temperature and solution pH on the ion exchange capacity were studied and it was found that the exchange capacity was slightly increased by augmenting the temperature and by decreasing the pH from 6 to 3. The ion exchange capacity was independent of the diameter of the zeolite particles. The reversibility of ion exchange was analyzed by desorbing the ammonia exchanged on the zeolite. The ion exchange was reversible when 1% NaCl solution was used as the desorbing solution, but more ammonia was desorbed using 1% KCl solution in the desorption step. It was concluded that a considerable amount of ammonia was exchanged on the clinoptilolite and that the exchange capacity was slightly dependent on the temperature and pH. Copyright © 2004 Society of Chemical Industry [source]

Physicochemical characterization of papain entrapped in ionotropically cross-linked kappa-carrageenan gel beads for stability improvement using Doehlert shell design

Mayur G. Sankalia
Abstract This work examines the influence of various process parameters on papain entrapped in cross-linked ,-carrageenan beads for improvement of its stability. A Doehlert shell design (DSD) was employed to investigate the effect of three process variables, namely ,-carrageenan concentration, KCl concentration, and hardening time, on the entrapment, time required for 50% enzyme release (T50), time required for 90% enzyme release (T90), and particle size. The beads were prepared by dropping the ,-carrageenan containing papain into a magnetically stirred KCl solution. Topographical characterization was carried out by scanning electron microscopy and entrapment was confirmed by Fourier transform infrared spectroscopy and differential scanning calorimetry. Stability testing was carried out according to the International Conference on Harmonization (ICH) guidelines for zone III and IV. A polymeric matrix was prepared with ,-carrageenan (3.5% w/v) and potassium chloride (0.5 M) using the ionotropic gelation method, with a hardening time of 20 min. Beads characterized by a spherical disc shape with a collapsed center, an absence of aggregates, an entrapment of 82.75%, a T90 value of 55.36 min, and a composite index of 88.55 were produced. The shelf-life of the enzyme-loaded beads was found to increase to 3.63 years compared with 1.01 years for the conventional formulation. It can be inferred that the proposed methodology can be used to prepare papain-loaded ,-carrageenan beads for stability improvement. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95: 1994,2013, 2006 [source]

Surface characterization of flax, hemp and cellulose fibers; Surface properties and the water uptake behavior

Alexander Bismarck
The surface characteristics of several natural fibers,flax, hemp and cellulose,were investigated using scanning electron microscopy, BET-surface area and zeta (,-) potential measurements. ,-Potential measurements using the streaming potential method were performed in order to study the water uptake behavior as well as the surface properties of several natural fibers. The influence of different flax-fiber separation methods and several modifications, like industrial purification, and such a treatment followed by alkaline purification as well as polypropylene grafting on the fiber surface morphology, surface area and time- and pH-depending ,-potentials were studied. The time-dependence of the ,-potential, measured in 1 mM KCl solution, offeres and alternative possibility to estimate the water uptake behavior for nearly all investigated natural fibers. The water uptake data derived from the ,-potential measurements (, = f(t)) were compared with data from conventional water adsorption studies for some chosen examples. [source]

Circular dichroism spectroscopy of conformers of (guanine + adenine) repeat strands of DNA

CHIRALITY, Issue 7 2003
Iva Kejnovská
Abstract (Guanine+adenine) strands of DNA are known to associate into guanine tetraplexes, homodimerize into parallel or antiparallel duplexes, and fold into a cooperatively melting single strand resembling the protein alpha helix. Using CD spectroscopy and other methods, we studied how this conformational polymorphism depended on the primary structure of DNA. The study showed that d(GGGA)5 and d(GGA)7 associated into homoduplexes at low salt or in the presence of LiCl but were prone to guanine tetraplex formation, especially in the presence of KCl. In addition, they yielded essentially the same CD spectrum in the presence of ethanol as observed with the ordered single strand of d(GA)10. Strands of d(GA)10, d(GGAA)5, d(GAA)7, and d(GAAA)5 associated into homoduplexes in both LiCl and KCl solutions, but not into guanine tetraplexes. d(GAAA)5 and d(GAA)7 further failed to form the single-stranded conformer in aqueous ethanol. Adenine protonation, however, stabilized the single-stranded conformer even in these adenine-rich fragments. The ordered single strands, homoduplexes as well as the guanine tetraplexes, all provided strikingly similar CD spectra, indicating that all of the conformers shared similar base stacking geometries. The increasing adenine content only decreased the conformer thermostability. Chirality 15:584,592, 2003. © 2003 Wiley-Liss, Inc. [source]