Topic
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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TL;DR: In this article, a detailed study on the electrocatalytic oxidation of β-nicotinamide adenine dinucleotide at three different carbon paste electrodes modified with redox mediators commonly used in bioelectrochemistry, viz Meldola blue, methylene green and riboflavin, adsorbed on zirconium phosphate Cyclic voltammetric investigations of these chemically modified electrodes performed in aqueous tris buffer solutions at different pHs allowed them to conclude that the immobilised redox species presented very stable redox properties, with mid
73 citations
TL;DR: In this paper, a three layer feed-forward network was used and the network training was performed using the back-propagation (BP) algorithm for signal processing of optical fiber pH sensor.
Abstract: In this paper, the applications of artificial neural network (ANN) in signal processing of optical fibre pH sensor is presented. The pH sensor is developed based on the use of bromophenol blue (BPB) indicator immobilized in a sol–gel thin film as a sensing material. A three layer feed-forward network was used and the network training was performed using the back-propagation (BP) algorithm. Spectra generated from the pH sensor at several selected wavelengths are used as the input data for the ANN. The bromophenol blue indicator, which has a limited dynamic range of 3.00–5.50 pH units, was found to show higher pH dynamic range of 2.00–12.00 and with low calibration error after training with ANN. The enhanced ANN could be used to predict the new measurement spectra from unknown buffer solution with an average error of 0.06 pH units. Changes of ionic strength showed minor effect on the dynamic range of the sensor. The sensor also demonstrated good analytical performance with repeatability and reproducibility characters of the sensor yield relative standard deviation (R.S.D.) of 3.6 and 5.4%, respectively. Meanwhile the R.S.D. value for this photostability test is 2.4% and it demonstrated no hysteresis when the sensor was cycled from pH 2.00–12.00–2.00 (acid–base–acid region) of different pH. Performance tests demonstrated a response time of 15–150 s, depending on the pH and quantity of the immobilized indicator.
73 citations
TL;DR: Citrate buffer was identified as the preferred buffer for lyophilized pharmaceuticals because of its higher Tg’ and a lower crystallization tendency.
Abstract: Purpose. To evaluate crystallization behavior and collapse temperature (Tg') of buffers in the frozen state, in view of its importance in the development of lyophilized formulations.
Methods. Sodium tartrate, sodium malate, potassium citrate, and sodium citrate buffers were prepared with a pH range within their individual buffering capacities. Crystallization and the Tg’ were detected during heating of the frozen solutions using standard DSC and modulated DSC.
Results. Citrate and malate did not exhibit crystallization, while succinate and tartrate crystallized during heating of the frozen solutions. The citrate buffer had a higher Tg’ than malate and tartrate buffers at the same pH. Tg’ vs. pH graphs for citrate and malate buffers studied had a similar shape, with a maximum in Tg’ at pH ranging from 3 to 4. The Tg’ maximum was explained as a result of a competition between two opposing trends: an increase in the viscosity of the amorphous phase because of an increase in electrostatic interaction, and a decrease in the Tg’ because of an increase in a water concentration of the freeze-concentrated solution.
Conclusion. Citrate buffer was identified as the preferred buffer for lyophilized pharmaceuticals because of its higher Tg’ and a lower crystallization tendency.
73 citations
TL;DR: A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements in water samples and relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels.
Abstract: A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCl solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 × 10–4 M). Finally, 1 × 10–5 M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 × 10–10 to 1.05 × 10–9 M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.
73 citations
TL;DR: In this paper, a rutheniumoxide-type catalytic film (RuOx) was produced on carbon fiber microelectrodes by cycling the electrode potential between 0.65 and −0.85V vs. SSCE at 100 V s−1 in an air-equilibrated acidic solution of RuCl3.
73 citations