Buffer solution

About: Buffer solution is a research topic. Over the lifetime, 6948 publications have been published within this topic receiving 112440 citations. The topic is also known as: pH buffer & buffer.

Effects of buffer pH on electroosmotic flow control by an applied radial voltage for capillary zone electrophoresis.

Abstract: Electroosmotic flow has been shown to be controlled via an applied radial voltage. Many factors determine the effectiveness of this control, and one major factor is buffer pH. In this study the effectiveness of the applied radial voltage for controlling electroosmotic flow while varying buffer pH is examined. Previously developed theory is applied and compared to experimental results for a pH range from 1.4 to 6.32. Analysis time is dramatically reduced by applying a radial voltage for separation of a peptide mixture at pH 1.4. Theory predicts laminar flow profiles under some conditions when applying this technique. However, experimental evidence at pH 6.32 and 1.4 shows no evidence of band broadening from a laminar flow profile. Theoretical and experimental results indicate the largest range of effective electroosmotic flow control via an applied radial voltage occurs at low ph. Furthermore, a sigmoidal relationship between electroosmotic flow and applied radial voltage is clearly apparent under these conditions. In contrast, at high buffer pH ( > 6) the relationship appears to be linear and is only over a limited range of flow velocities.

Chiral separation of β-amino alcohols by capillary electrophoresis using cyclodextrins as buffer additives. I. Effect of varying operating parameters

Abstract: Capillary electrophoresis has been used for the chiral analysis of two β-amino alcohol pharmaceutical compounds. Capillary zone electrophoresis conditions were used with β-cyclodextrin as a chiral mobile phase additive. The effects of variation of β-cyclodextrin concentration, temperature, pH, background electrolyte composition and concentration have been investigated. Optimum separations were achieved for clenbuterol using β-cyclodextrin at its solubility limit (16mM), the lowest practicable temperature (19°C), pH 4.0 and an electrolyte solution with a high ionic strength prepared from 0.1 M citric acid and 0.3 M Na2HPO4. For the development compound picumeterol and its (S)-enationmer, the optimum pH 4.0 buffer was prepared from 0.1 M citric acid and 0.2 M sodium acetate. Baseline separation with resolution greater than 2 was achieved for both compounds.

Mixed potential response mechanism of cobalt electrodes toward inorganic phosphate

Abstract: The potentiometric response mechanism of a previously reported phosphate ion-sensitive electrode based on a surface-oxidized cobalt metal is examined. Beyond response to phosphate, the cobalt electrode is found to respond to changes in the partial pressure of oxygen in the sample solution. The potentiometric response toward phosphate ions and molecular oxygen is shown to depend on the sample stirring rate as well as the pH, ionic strength, and nature of the buffer salts present within the test solution. X-ray photoelectron spectroscopy studies of the cobalt electrodes, in conjunction with cyclic voltammetric measurements, suggest that the potentiometric response originates from a mixed potential resulting from the slow oxidation of cobalt and simultaneous reduction of both oxygen and Co2+ at the surface of the electrode. In contrast to an originally proposed host−guest mechanism, the present mixed potential mechanism more accurately explains behavior of oxidized cobalt electrodes in the presence of phosph...

Coupled Oxidation of Alcohol

Abstract: We have seen previously that hydrogen peroxide is formed in several oxidation reactions catalysed by enzymes like xanthine oxidase, uricase, and amino acid oxidase. In all these reactions one molecule of hydrogen peroxide is formed for each molecule of substrate oxidized. It is known that the hydrogen peroxide formed in the primary oxidation reaction can be used in promoting secondary or coupled oxidations of some substances (Thurlow, 1925; Harrison and Thurlow, 1926). The study of secondary oxidations by hydrogen peroxide revealed an unsuspected fact, namely, that it can be used in the oxidation of alcohol to the corresponding aldehydes. In this paper we propose to examine the conditions under which the coupled oxidation of alcohol takes place, the properties of the peroxide formed in the primary reaction, and the mechanism of the secondary oxidation of alcohol promoted by this peroxide. II−Coupled Oxidation of Alcohol by Uricase System. The study of this reaction was carried out in Barcroft differential manometers in the usual manner but with a series of controls. For instance, in order to detect the oxidation of alcohol by the uricase system, the oxygen uptake of four mixtures was measured separately: (1) uricase + uric acid; (2) uricase + alcohol; (3) uricase + uric acid + alcohol; (4) uric acid + alcohol. The reactions were carried out in buffer solution of p H 8·9 at 39° C. The quantity of enzyme varied from 25 to 50 mg of dry acetone preparation of liver, that of uric acid varied from 2 to 5 mg, and of alcohol from 5 to 10 mg per flask. The CO2 was absorbed in the usual way by rolls of filter paper soaked with 10% KOH. The substrate in these experiments was always added in small dangling tubes suspended from the KOH tubes. These tubes were dislodged and their contents mixed with that of the flask after equilibration of the temperature and closing the taps of the manometers. After the experiment the contents of the flasks were examined for aldehydes. In manometric experiments with uricase the presence of KOH is required for absorption of CO2, and most of the aldehyde is absorbed by the potash paper where it polymerizes to a dark brown substance. In this way, even a small amount of aldehyde formed from alcohol gives rise to a yellow fringe on the potash filter paper.

Cadmium ion adsorption on different carbon adsorbents from aqueous solutions. Effect of surface chemistry, pore texture, ionic strength, and dissolved natural organic matter

Abstract: Adsorption of Cd(II) species at pH = 5 was studied on three carbon adsorbents: granular activated carbon, activated carbon fiber, and activated carbon cloth As-received and oxidized adsorbents were used Cd(II) adsorption greatly increased after oxidation due to the introduction of carboxyl groups The use of a buffer solution to control the pH introduced some changes in the surface chemistry of carbons through the adsorption of one of the compounds used, biphthalate anions The increase in ionic strength reduced Cd(II) uptake on both as-received and oxidized carbons due to a screening of the electrostatic attractions between the Cd(II) positive species and the negative surface charge, which in the case of as-received carbons derived from the biphthalate anions adsorbed and in the oxidized ones from the carboxyl groups Tannic acid was used as a model compound for natural organic matter Its adsorption was greatly reduced after oxidation, and most of the carbon adsorbents preadsorbed with tannic acid showed an increase in Cd(II) uptake In the case of competitive adsorption between Cd(II) species and tannic acid molecules, there was a decrease in Cd(II) uptake on the as-received carbon whereas the contrary occurred with the oxidized carbons These results illustrate the great importance of carbon surface chemistry in this competitive adsorption process Finally, under all experimental conditions used, when the adsorption capacity of carbons was compared under the same conditions it increased in the following order: granular activated carbon < activated carbon fiber < activated carbon cloth