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.

750-MHz directly coupled HPLC-NMR: Application for the sequential characterization of the positional isomers and anomers of 2-, 3-, and 4-fluorobenzoic acid glucuronides in equilibrium mixtures

Abstract: This paper presents the first demonstration of the use of directly coupled HPLC. 1 H NMR spectroscopy using 750-MHz NMR detection. We show the application of the technique in the continuous-flow mode to separate and characterize mixtures of ester glucuronide isomers formed by internal acyl migration and mutarotation of 2-, 3-, and 4-fluorobenzoic acid β-1-O-acyl glucuronides [1-O-(2-fluorobenzoyl)-D-glucopyranuronic acid, 1-O-(3-fluorobenzoyl)-D-glucopyranuronic acid, and 1-O-(4-fluorobenzoyl)-D-glucopyranuronic acid]. The equilibrated mixtures of isomers were obtained by incubation of 10 mM synthetic β-1-O-acyl glucuronides in buffer solution (pH 7.4) at 25 °C. The β-anomer of the residual 1-O-acyl-glucuronide, as well as the 2-, 3-, and 4-positional glucuronide isomers (all three as both α- and β-anomers) present in the equilibrium mixture, was separated in the chromatographic system, and the 2-, 3- and 4-positional glucuronide isomers could be characterized directly by HPLC-NMR in the continuous-flow mode. The amount of each isomer injected on column was <0.14 μmol (35 μg), showing the practicality of continuous-flow 750-MHz HPLC-NMR in analytical problems requiring the highest sensitivity and signal dispersion.

Properties of Amylase Immobilized on a New Reversibly Soluble-Insoluble Polymer and Its Application to Repeated Hydrolysis of Soluble Starch

Abstract: A copolymer of glycidyl methacrylate (GMA) and N-isopropyl acrylamide (NIPAM) forms a reversibly soluble-insoluble (S-IS) polymer (GMA-NIPAM), whose solubility changes with the temperature of the solution An amylase (Dabiase) was immobilized on GMA-NIPAN under alkaline conditions The specific activity of Dabiase immobilized on GMA-NIPAM (D-GN) for saccharification of soluble starch was 90% that of native Dabiase and higher than that of conventional solid immobilized enzymes D-GN was soluble below 32°C but insoluble above 44°C When NaCl was added to a buffer solution (pH 50) with D-GN, the solubility response of D-GN to change in temperature was more sensitive than that in the buffer solution without NaCl In addition, the temperature causing half of the maximum turbidity decreased by about 23°C whenever the NaCl concentration of the buffer solution was increased by 1% D-GN was used successively for repeated hydrolysis reaction of soluble starch, in which D-GN was insolubilized not only by elevating the temperature of reaction mixture with 1% NaCl from 30°C to 38°C, but also by adjusting the NaCl concentration of reaction mixture to 4% at 30°C, followed by its batchwise recovery from a reaction product by centrifugation

Pilocarpine-loaded chitosan-PAA nanosuspension for ophthalmic delivery.

Abstract: Chitosan-poly(acrylic acid) (CS-PAA) nanoparticles, to be used as ophthalmic drug carrier, were successfully prepared using template polymerization of acrylic acid (AA) in a chitosan solution. When the polymerization was done at 70°C for 45 min with a CS/AA weight ratio of 1:1, the surface structure of the prepared nanoparticles was most stable with the smallest mean diameter (92.0±7.5 nm) and a stable zeta potential (25.5±2.6 mV) in a buffer solution (pH 4.5). The size of the nanoparticles dramatically increased with the pH value of the medium. Both in vitro and in vivo studies revealed that the prepared nanoparticle suspension was better at sustaining the release of pilocarpine than either simulated tear fluid or commercial eye drops.