Sulfated Polyborate, a novel buffer for low pH mobile phase on a non-end capped stationary phase in reverse phase liquid chromatography

Background: Sulfated Polyborate, a novel inorganic material primarily designed as a catalyst, has shown properties such as high solubility in organic solvents, low U.V. cut-off, and pKa ≈2.0, which suggests its potential as a mobile phase buffer for reverse-phase liquid chromatography. Objective: This study aims to substantiate the role of Sulfated Polyborate as mobile phase buffer for reverse-phase liquid chromatographic analysis of basic drugs with high pKa values viz. Bisoprolol fumarate, Timolol maleate, Verapamil hydrochloride, and Carvedilol. Methods: Solubilities, U.V. cut-offs, and pKa of Sulfated Polyborate was first experimentally confirmed. The behaviour of Sulfated Polyborate as mobile phase buffer at pH 3.0 was ascertained by varying the buffer concentration, flow rates, and percent organic modifier for elution of the four basic drugs on a non-end capped octyl silyl (C8) column. Similarly, the study was performed with KH2PO4 as a reference buffer. The column performance and conductometric measurements ascertained the impact of Sulfated Polyborate on the stationary phase. Results: Sulfated Polyborate and KH2PO4 buffers showed correlation coefficients of 0.99 and 1.00 for analyte retention factors for variation of buffer concentration and organic modifier composition, respectively. Peak symmetries and the number of theoretical plates were improved from > 2.0 to < 2.0 and ≈1000 to ≈3000, respectively, for Variation in buffer concentrations. Similar Van Deemter plots indicated equivalency of Sulfated Polyborate and KH2PO4 buffers. The column performance and conductometric measurements depicted no adsorption on the stationary phase. Conclusion: The present study demonstrates Sulfated Polyborate as a novel buffer for analytes with higher pKa on reverse-phase liquid chromatography.

Effects of Buffer Concentration on the Sensitivity of Silicon Nanobelt Field-Effect Transistor Sensors

In this work, a single-crystalline silicon nanobelt field-effect transistor (SiNB FET) device was developed and applied to pH and biomolecule sensing. The nanobelt was formed using a local oxidation of silicon technique, which is a self-aligned, self-shrinking process that reduces the cost of production. We demonstrated the effect of buffer concentration on the sensitivity and stability of the SiNB FET sensor by varying the buffer concentrations to detect solution pH and alpha fetoprotein (AFP). The SiNB FET sensor was used to detect a solution pH ranging from 6.4 to 7.4; the response current decreased stepwise as the pH value increased. The stability of the sensor was examined through cyclical detection under solutions with different pH; the results were stable and reliable. A buffer solution of varying concentrations was employed to inspect the sensing capability of the SiNB FET sensor device, with the results indicating that the sensitivity of the sensor was negatively dependent on the buffer concentration. For biomolecule sensing, AFP was sensed to test the sensitivity of the SiNB FET sensor. The effectiveness of surface functionalization affected the AFP sensing result, and the current shift was strongly dependent on the buffer concentration. The obtained results demonstrated that buffer concentration plays a crucial role in terms of the sensitivity and stability of the SiNB FET device in chemical and biomolecular sensing.

Local Acidification Limits the Current Production and Biofilm Formation of Shewanella oneidensis MR-1 With Electrospun Anodes

The anodic current production of Shewanella oneidensis MR-1 is typically lower compared to other electroactive bacteria. The main reason for the low current densities is the poor biofilm growth on most anode materials. We demonstrate that the high current production of Shewanella oneidensis MR-1 with electrospun anodes exhibits a similar threshold current density as dense Geobacter spp biofilms. The threshold current density is a result of local acidification in the biofilm. Increasing buffer concentration from 10 to 40 mM results in a 1.8-fold increase of the current density [(590 ± 25) μA cm−2] while biofilm growth stimulation by riboflavin has little effect on the current production. The current production of a reference material below the threshold did not respond to the increased buffer concentration but could be enhanced by supplemented riboflavin that stimulated the biofilm growth. Our results suggest that the current production with S. oneidensis is limited (1) by the biofilm growth on the anode that can be enhanced by the choice of the electrode material, and (2) by the proton transport through the biofilm and the associated local acidification.

Extraction of ingredients from tea leaves using oxidative enzymatic reaction and optimization of extraction conditions

Peroxidase (POD) and polyphenol oxidase (PPO) are used as biocatalyst in many processes such as oxidization reactions, wastewater treatment, phenol synthesis and so on. The purpose of current study is enzymes extraction from biomass (tea leaves) as well as evaluation of their activation. Different parameters including temperature, buffer concentration, buffer type, buffer/tea leaves ratio, addition of high molecular weight polymers and emulsifiers, and pH were optimized in order to obtain the highest enzymes activity. Response Surface Methodology (RSM) procedure is employed for statistical analysis of enzymes extraction. It is understood from the result that PPO and POD possess the highest activity at temperatures of 25 °C and 50 °C, pH 7 and 5, buffer molarity of 0.1, and 0.05, buffer/tea leaves ratio = 5 for both, contact time = 20 min and 10 min, and presence of 6% and 3% PVP, 5% and 0% Tween 80 for PPO and POD, respectively. Amounts of highest activity for PPO and POD biocatalysts were calculated 0.42 U/mL and 0.025493 U/mL, respectively. Moreover, the entire inactivation of PPO took place after 30 min at 40 °C and 60 °C and 20 min at 80 °C. However, POD lost 35% of its activity after 30 min at 40 °C and 60 °C. The amount of 6% POD activity was kept after 45 min at 80 °C. Generally, it was indicated that POD was more resistant to thermal treatment than PPO.

Development and validation of a short runtime method for separation of trace amounts of 4-aminophenol, phenol, 3-nitrosalicylic acid and mesalamine by using HPLC system

In a short runtime process (about 6 minutes), with isocratic method without need of reconditioning before the next run, a mixture of some molecules containing 4-aminophenol (4APh), phenol, 3-nitrosalicylic acid (3NSA), and mesalamine (5-aminosalicylic acid) (MLZ), were separated and detected by means of HPLC/UV-Vis system. The resolutions of the separated and sharp peaks referring to the mentioned compounds were at least more than 2, and the tailing factor (TF) was about 1, even in 1 µg/l (ppm) concentration. In order to optimize the method, the effects of the pH, eluent percentage, flow rate, and buffer concentration, and wavelength on the chromatogram were investigated. Also, the results of the validation processes showed that the method trustable to be used in laboratories.

Glucose Oxidase Kinetics using MnO2 Nanosheets: Confirming Michaelis – Menten Kinetics and Quantifying Decreasing Enzyme Performance with Increasing Buffer Concentration

MnO2 nanosheets and ultraviolet-visible (UV-Vis) absorbance spectroscopy are used to study glucose oxidase (GOx) kinetics. Glucose oxidation by GOx produces H2O2, which rapidly decomposes the nanosheets and reduces their absorption....