Electrochemical Measurements of Glucose Using a Micro Flow‐Through Immobilized Enzyme Reactor

A new fast, cheap and efficient epoxy‐amine immobilized enzyme reactor (IMER) is demonstrated. Polyethyleneimine (PEI) was used as the curing agent of an epoxy resin (bisphenol‐A diglycidyl ether (BADGE)) in order to introduce a high number of reactive –NH₂ groups at the substrate. A ratio mixture of 3:2 PEI:BADGE (w/w) was shown to be the most suitable for curing, taking into account the number of immobilization sites and the resistance of the material towards channeling. Electrochemical measurements made by a three electrode system, adapted at the IMER, showed that the K_m value for immobilized glucose oxidase (GOx) was half the value commonly reported for GOx immobilized at PEI derived substrates. The IMER response decreased by around 41 % after one week of intense usage. Even so, the remaining activity was sufficient for quantifications of approximately 0.1 mmol L⁻¹, merely requiring a new calibration of the reactor before its utilization. The developed system was applied to D‐glucose quantification of beverage samples, requiring an injection volume of only 10 μL and a flow rate of 150 μL min⁻¹ (almost 60 samples per hour). Low detection and quantification limits (1.94 and 5.89 μmol L⁻¹, respectively) and a wide linear range (from 8 μmol L⁻¹ to 2 mmol L⁻¹) were also found, which are useful characteristics for quality control analysis.     

An original ultrasonic reaction with dual coaxial frequencies for biomass processing

An advanced dual frequency ultrasonic coaxial reactor enabling simultaneously low and high frequencies irradiating in the same direction was developed to focus both mechanical and chemical effects on a concentrated area. The prototype was straightforward employed for the conversion of a starch-based industrial waste into sugars.     

Energy dispersive X-ray fluorescence determination of cadmium in uranium matrix using Cd Kα line excited by continuum

An energy dispersive X-ray fluorescence method for determination of cadmium (Cd) in uranium (U) matrix using continuum source of excitation was developed. Calibration and sample solutions of cadmium, with and without uranium were prepared by mixing different volumes of standard solutions of cadmium and uranyl nitrate, both prepared in suprapure nitric acid. The concentration of Cd in calibration solutions and samples was in the range of 6 to 90 µg/mL whereas the concentration of Cd with respect to U ranged from 90 to 700 µg/g of U. From the calibration solutions and samples containing uranium, the major matrix uranium was selectively extracted using 30% tri-n-butyl phosphate in dodecane. Fixed volumes (1.5 mL) of aqueous phases thus obtained were taken directly in specially designed in-house fabricated leak proof Perspex sample cells for the energy dispersive X-ray fluorescence measurements and calibration plots were made by plotting Cd Kα intensity against respective Cd concentration. For the calibration solutions not having uranium, the energy dispersive X-ray fluorescence spectra were measured without any extraction and Cd calibration plots were made accordingly. The results obtained showed a precision of 2% (1σ) and the results deviated from the expected values by < 4% on average.     

Analytical Model of a Plasma Reactor

This paper presents a simple analytical model to estimate the effect of theboundary layer on the performance of a dc plasma reactor. A graphite linerwas inserted inside the reactor to raise the wall temperature. The model wasused to predict the Destruction and Removal Efficiency (DRE) of the reactorwith and without the graphite liner. The DRE of the device was measured forboth conditions and was found to be in close agreement with the predictedvalues. The model has shown that the DRE is a strong function of the walltemperature of the flight tube and is insensitive to the change in thetube's diameter.     

原子吸收光谱法测定过氧化氢-柠檬酸溶液中铁铬镍钴

研究了原子吸收光谱法测定压水堆主回路去污液过氧化氢-柠檬酸溶液中铁、铬、镍、钴的影响因素,选择了合适的测量条件,用合成样品进行了试验.结果表明.铁、钴、镍、铬含量在0.5～5mg·L~(-1)范围的回收率为100%±10%,相对标准偏差为6.0%～10%.     

Electrochemical conversion of carbon dioxide in a solid oxide electrolysis cell

Carbon dioxide is one of the greatest concerns worldwide, since it is not only a major greenhouse gas but also expected to be an important, sustainable resource for fuels and chemicals. The electrochemical conversion of carbon dioxide, based on solid electrolyte membrane reactors, has the promise to overcome the limitations of the conventional catalytic reactors such as the limited conversion and kinetics, relatively low selectivity and high energy consumption. In this review, electrocatalysts and solid oxide electrolytes, both proton and oxide ion conductors as core materials in an electrochemical ceramic membrane reactor have been reviewed and particular emphasis is placed on their application to synthesize carbon monoxide and hydrogen.     

Production of Carbon Nanotubes over Pre-reduced LaCoO_3 Using Fluidized-bed Reactor

A great amount of research on carbon nanotubes (CNTs) has been carried out since its observation in 19911. It has been predicted that CNTs can be novel materials of semiconductor, electric-field-induced electron emitters, quantum wire, catalysts etc2-5. Nowadays, CNTs can be synthesized by arc discharge6 laser ablation7, and pyrolysis of hydrocarbon gases8. In order to make CNTs of practical importance, the criteria for assessing any synthesis technique must include the feasibility and po…     

Immobilized enzyme reactor chromatography: optimization of protein retention and enzyme activity in monolithic silica stationary phases

Our group recently reported on the application of protein-doped monolithic silica columns for immobilized enzyme reactor chromatography, which allowed screening of enzyme inhibitors present in mixtures using mass spectrometry for detection. The enzyme was immobilized by entrapment within a bimodal meso/macroporous silica material prepared by a biocompatible sol-gel processing route. While such columns proved to be useful for applications such as screening of protein-ligand interactions, significant amounts of entrapped proteins leached from the columns owing to the high proportion of macropores within the materials. Herein, we describe a detailed study of factors affecting the morphology of protein-doped bioaffinity columns and demonstrate that specific pH values and concentrations of poly(ethylene glycol) can be used to prepare essentially mesoporous columns that retain over 80% of initially loaded enzyme in an active and accessible form and yet still retain sufficient porosity to allow pressure-driven flow in the low μL/min range. Using the enzyme γ-glutamyl transpeptidase (γ-GT), we further evaluated the catalytic constants of the enzyme entrapped in capillary columns with different silica morphologies as a function of flowrate and backpressure using the enzyme reactor assay mode. It was found that the apparent activity of the enzyme was highest in mesoporous columns that retained high levels of enzyme. In such columns, enzyme activity increased by ∼2-fold with increases in both flowrate (from 250 to 1000 nL/min) and backpressure generated (from 500 to 2100 psi) during the chromatographic activity assay owing to increases in k_cat and decreases in K_M, switching from diffusion controlled to reaction controlled conditions at ca. 2000 psi. These results suggest that columns with minimal macropore volumes (<5%) are advantageous for the entrapment of soluble proteins for bioaffinity and bioreactor chromatography.