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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.


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Journal ArticleDOI
TL;DR: In this paper, the electron paramagnetic resonance (EPR) spectrum obtained was assigned to the semiquinone radical anion of Hypocrellin A (HA.− ) based on a series of experimental results.
Abstract: Hypocrellin A (HA) is an efficient phototherapeutic agent. Illumination of HA in dimethylsulphoxide (DMSO) or DMSO-buffer (1:1 by volume, pH > 6.7) generated a strong electron paramagnetic resonance (EPR) signal. This EPR signal was intensified in the presence of reductants. The EPR spectrum obtained was assigned to the semiquinone radical anion of HA (HA .− ) based on a series of experimental results. Decay of HA .− , attributed to a radical-radical reaction, follows second-order kinetics. In acidic DMSO-buffer (1:1 by volume) solution, no EPR signal of HA .− was detected in the absence or presence of reductant. This was explained by a fast disproportionation of radicals, facilitated by protonation of radicals. The spectrophotometric measurements indicated that on illumination HA was directly reduced to its two-electron reduction product, i.e. hydroquinone, in acidic solution. The absorption maximum of the hydroquinone of HA which is at 496 nm at pH 5.8 shifts bathochromically with increase in pH of the medium. In DMSO or DMSO-buffer (1:1 by volume, pH > 6.7) solutions the semiquinone radical anion of HA was also observed spectrophotometrically. The absorption maximum of HA .− is at around 628 nm. Strong intramolecular hydrogen bonding was considered to exist in the chromophore of HA .− .

38 citations

Journal ArticleDOI
TL;DR: In this article, a glassy carbon electrode coated with graphene nanosheets, chitosan and a poly (amidoamine) dendrimer in pH 6.0 buffer solution was investigated.
Abstract: The electrochemical behavior of rutin was investigated in pH 6.0 buffer solution using a glassy carbon electrode coated with graphene nanosheets, chitosan and a poly (amidoamine) dendrimer in pH 6.0 buffer solution. The results indicate that the modified electrode displays electrochemical redox activity towards rutin, and that the oxidation peak current of rutin increases significantly compared to that at other electrodes. The amount of immobilized graphene and dendrimer, pH value, scan rate, accumulation time and accumulation potential were optimized. The kinetic parameters, charge transfer coefficient, transfer electron number, proton transfer number, standard rate constant, were calculated. Under the optimized conditions, the oxidation peak current is proportional to the concentration of rutin in the range between 0.001 and 2.0 μmol L−1 (R = 0.9991). The detection limit is 0.6 nmol L−1 (at S/N = 3). The electrode exhibits satisfactory selectivity and reproducibility and was applied to the determination of rutin in pharmaceutical preparations, spiked human serum, and traditional Chinese medicine, with recoveries between 97.2 and 104.67%.

38 citations

Journal ArticleDOI
15 Apr 2010-Talanta
TL;DR: A novel non-enzymatic hydrogen peroxide sensor was realized from Mn-nitrilotriacetate acid (Mn-NTA) nanowires, which were successfully fabricated via a facile hydrothermal route and showed linear response to H( 2)O(2) at the concentrations range from 5 x 10(-6)M to 2.5 x 10 (-3)M.

38 citations

Journal ArticleDOI
TL;DR: In this article, the formation and reduction of the passive film on iron was investigated in a phosphate-borate buffer solution, and it was concluded that the ferric oxide was simultaneously reduced to metallic iron and ferrous ion at the potential arrest.

38 citations

Journal ArticleDOI
TL;DR: In this article, a directly coupled HPLC-1 H NMR was used in the stop-flow mode to separate and rapidly identify an equilibrated mixture of ester glucuronide isomers formed spontaneously by intramolecular rearrangement reactions (internal acyl migration and mutarotation) of 2-fluorobenzoic acid β-1-glucuronide (1-O-(2-florobenzoyl)-D-glocopyranuronic acid).
Abstract: Directly coupled HPLC- 1 H NMR was used in the stop-flow mode to separate and rapidly identify an equilibrated mixture of ester glucuronide isomers formed spontaneously by intramolecular rearrangement reactions (internal acyl migration and mutarotation) of 2-fluorobenzoic acid β-1-glucuronide (1-O-(2-fluorobenzoyl)-D-glucopyranuronic acid). The equilibrated mixture of isomers was obtained by incubation of the synthetic 2-fluorobenzoic acid glucuronide in buffer solution (pH 7.4) at 25 °C for 24 h. The β-anomer of the 1-O-acyl glucuronide, and the 2-, 3-, and 4-positional glucuronide isomers (all three as both α- and β-anomers) present in the equilibrium mixture, were all characterized after separation in an isocratic chromatographic system containing phosphate buffer at pH 7.4 and 1% acetonitrile in the mobile phase. The HPLC-NMR investigations also elucidated the mutarotation of the positional glucuronide isomers as well as showing the benefits of the HPLC-NMR technique as a primary analytical tool. This HPLC-NMR method will be of particular value in studies on the acyl migration reactions of nonsteroidal antiinflammatory drug glucuronides which may be related to their toxicological properties.

38 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202317
202232
202185
2020151
2019220
2018245