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.

Simultaneous determination of hydroquinone and catechol using a modified glassy carbon electrode by ruthenium red/carbon nanotube

Abstract: A decorated glassy carbon (GC) electrode with functionalized multi-walled carbon nanotube (CNTs) and ruthenium red (RR) has been used for simultaneous determination of hydroquinone (HQ) and catechol (CC). The electrocatalytic behaviors of the GC/CNTs–RR were studied in acetate buffer solution with pH 4.5 by differential pulse voltammetry and chronoamperometry techniques. Due to the excellent electrocatalytic activity and enhanced electrical conductivity of the CNTs–RR, the simultaneous determination of HQ and CC with two well-defined peaks was achieved at the GC/CNTs–RR modified electrode. The catalytic peak currents linearly depend on the HQ and CC concentrations in the range of 1.3–433.3 µM with the sensitivity of 5.0 µA µM−1 cm−2 and 7.45 µA µM−1 cm−2, respectively. The detection limits for HQ and CC were obtained 0.21 and 0.18 µM. The diffusion coefficient for the oxidation of HQ and CC at the modified electrode was calculated as 1.06 ± 0.05 × 10−6 and 1.76 ± 0.07 × 10−5 cm2 s−1, respectively. The proposed sensor was successfully examined for real water samples analysis and revealed stable and reliable recovery data.

Amino Acid Determination Using Screen-Printed Electrochemical Sensors

Abstract: The use of a screen-printed electrochemical sensor (SPES) strip, consisting of a two-electrode system (a carbon working electrode and Ag/AgCl reference electrode), for amino acid determination is reported. The behaviour of the SPES toward cysteine and tyrosine is investigated using linear sweep and hydrodynamic voltammetries. The SPES operate at a lower oxidation potential (vs. Ag/AgCl) compared with traditional carbon and platinum electrodes, in a buffer solution (pH = 7) prepared using 0.1 M phosphates and 0.1 M KCl. The linear response lies between 5 * 10−5 M and 5 * 10−4 M for both amino acids while the sensitivity is 2.95±0.03 µA mM−1 for cysteine and 8.00±0.01 µA mM −1for tyrosine; the correlation coefficient is higher than 0.9980. The sensors were applied to the analysis of some commercial pharmaceutical samples, and the results suggested that the devices hold promise in this application area.

Reversed micelles of polymeric surfactants in nonpolar organic solvents. A new microheterogeneous medium for enzymatic reactions.

Abstract: A new microheterogeneous non-aqueous medium for enzymatic reactions, based on reversed micelles of a polymeric surfactant, was suggested. The surfactant termed CEPEI, was synthesized by successive alkylation of poly(ethy1eneimine) with cetyl bromide and ethyl bromide and was found to be able to solubilize considerable amounts of water in benzeneln-butanol mixtures. The hydrodynamic radius of polymeric-reversed micelles was estimated to be in the range 22 - 51 nm, depending on the water content of the system, as determined by means of the quasi-elastic laser-light scattering. Polymeric reversed micelles were capable of solubilizing enzymes (a-chymotrypsin and laccase) in nonpolar solvents with retention of catalytic activity. Due to the strong buffering properties of CEPEI over a wide pH range, it could maintain any adjusted pH inside hydrated reversed micelles. It was found that catalytic behavior of enzymes entrapped in polymeric reversed micelles was rather insensitive to the pH of the buffer solution introduced into the system as an aqueous component, but determined mostly by acid-base properties of the polymeric surfactant itself. Both catalytic activity and stability of entrapped a-chymotrypsin and laccase were found to increase with increasing water content of the system. Under certain conditions, the entrapment of a-chymotrypsin into CEPEI reversed micelles resulted in a considerable increase in catalytic activity and stability as compared to aqueous solution. CEPEI reversed micelles were demonstrated to be promising enzyme carriers for use in membrane reactors. Owing to the large dimensions of CEPEI reversed micelles, they are effectively kept back by a semipermeable membrane, thus allowing an easy separation of the reaction product and convenient recovery of the enzyme.