Urolithiasis remains a major medical problem in China, especially in Guangdong Province in the southest of China[1]. A survey in Shenzhen city, the most southern city in China, showed the incidence of renal calculus was 4.87%, being 6.12% in the males and 4.07% in the females[2]. The prevalence of renal calculus has been more as the age advances and in the male population and so was in the less-educated population. The recurrence rate is more than 80%, with a moderate improvement by conventi… 相似文献
Summary Solubility of calcium sulfate in concentrated aqueous chloride solutions is of particular significance in chloride hydrometallurgy
and various crystallization processes, such as the production of potassium sulfate from phosphogypsum and potassium chloride.
This paper examines an example of the second type of application in which gypsum and potassium chloride are reacted to form
K2SO4. The solubility of phosphogypsum in aqueous solutions of KCl, HCl, and mixtures of both has first been measured at various
temperatures and concentrations. The parameters investigated are HCl concentration up to 6M, KCl concentration up to 180 g
L-1 and temperature from 25 to 80°C. In addition, the influence of co-existing chloride salts, such as (HCl+KCl), on the solubility
of calcium sulfate is estimated from 25 to 80°C. The solubility increases obviously with the temperature increment as it does
initially with acid concentration, reaching a maximum of about 3M HCl, 130 g L-1 KCl and then drops. At the same time, the solubility of CaSO4·2H2O decreases with increasing KCl concentration. 相似文献
A new H2O2 enzymeless sensor has been fabricated by incorporation of thionin onto multiwall carbon nanotubes (MWCNTs) modified glassy carbon electrode. First 50 μL of acetone solution containing dispersed MWCNTs was pipetted onto the surface of GC electrode, then, after solvent evaporations, the MWCNTs modified GC electrode was immersed into an aqueous solution of thionin (electroless deposition) for a short period of time <5–50 s. The adsorbed thin film of thionin was found to facilitate the reduction of hydrogen peroxide in the absence of peroxidase enzyme. Also the modified electrode shows excellent catalytic activity for oxygen reduction at reduced overpotential. The rotating modified electrode shows excellent analytical performance for amperometric determination of hydrogen peroxide, at reduced overpotentials. Typical calibration at ?0.3 V vs. reference electrode, Ag/AgCl/3 M KCl, shows a detection limit of 0.38 μM, a sensitivity of 11.5 nA/μM and a liner range from 20 μM to 3.0 mM of hydrogen peroxide. The glucose biosensor was fabricated by covering a thin film of sol–gel composite containing glucose oxides on the surface of thionin/MWCNTs modified GC electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The detection limit, sensitivity and liner calibration rang were 1 μM, 18.3 μA/mM and 10 μM–6.0 mM, respectively. In addition biosensor can reach 90% of steady currents in about 3.0 s and interference effect of the electroactive existing species (ascorbic acid–uric acid and acetaminophen) is eliminated. The usefulness of biosensor for direct glucose quantification in human blood serum matrix is also discussed. This sensor can be used as an amperometric detector for monitoring oxidase based biosensors. 相似文献
A novel flow-injection amperometric method was proposed for the sensitive and enzymeless determination of hydrogen peroxide based on its electrocatalytic reduction at a palladium nanoparticle-modified pretreated pencil graphite electrode in a laboratory-constructed electrochemical flow cell. Cyclic voltammograms of the unmodified and modified electrodes were recorded in pH 7.0 phosphate buffer containing 0.10 M KCl at a scan rate of 50?mV s?1 for the investigation of electrocatalytic reduction of hydrogen peroxide at the palladium nanoparticle-modified pretreated pencil graphite electrode. Cyclic voltammograms of the pretreated pencil graphite electrode revealed an irreversible oxidation peak and a weak reduction peak of hydrogen peroxide at +1100?mV and –450?mV vs. an Ag/AgCl/KCl saturated reference electrode. However, the reduction of hydrogen peroxide was observed at –100?mV with an increase in current in the cyclic voltammograms of the palladium nanoparticle-modified pretreated pencil graphite electrode compared to the unmodified electrode. These results indicate that the palladium nanoparticle-modified pretreated pencil graphite electrode exhibits efficient electrocatalytic activity for the reduction of hydrogen peroxide. A linear concentration range was obtained between .01 and 10.0?mM hydrogen peroxide with a detection limit of 3.0 µM from flow injection amperometric current–time curves recorded in pH 7.0 phosphate buffer at –100?mV and a 2.0?mL min?1 flow rate. The novelty of this work relies on its use of a laboratory-constructed flow cell constructed for the pencil graphite electrode using these inexpensive, disposable, and electrochemically reactive modified electrodes for the amperometric determination of hydrogen peroxide in a flow injection analysis system. 相似文献
The construction and performance under flow-injection conditions of an integrated amperometric biosensor for hydrogen peroxide is reported. The design of the bioelectrode is based on a mercaptopropionic acid (MPA) self-assembled monolayer (SAM) modified gold disk electrode on which horseradish peroxidase (HRP, 24.3 U) was immobilized by cross-linking with glutaraldehyde together with the mediator tetrathiafulvalene (TTF, 1 μmol), which was entrapped in the three-dimensional aggregate formed.
The amperometric biosensor allows the obtention of reproducible flow injection amperometric responses at an applied potential of 0.00 V in 0.05 mol L−1 phosphate buffer, pH 7.0 (flow rate: 1.40 mL min−1, injection volume: 150 μL), with a range of linearity for hydrogen peroxide within the 2.0 × 10−7–1.0 × 10−4 mol L−1 concentration range (slope: (2.33 ± 0.02) × 10−2 A mol−1 L, r = 0.999). A detection limit of 6.9 × 10−8 mol L−1 was obtained together with a R.S.D. (n = 50) of 2.7% for a hydrogen peroxide concentration level of 5.0 × 10−5 mol L−1. The immobilization method showed a good reproducibility with a R.S.D. of 5.3% for five different electrodes. Moreover, the useful lifetime of one single biosensor was estimated in 13 days.
The SAM-based biosensor was applied for the determination of hydrogen peroxide in rainwater and in a hair dye. The results obtained were validated by comparison with those obtained with a spectrophotometric reference method. In addition, the recovery of hydrogen peroxide in sterilised milk was tested. 相似文献