Separation of peptides by strong cation-exchange capillary electrochromatography

Separation of small peptides on ion-exchange capillary electrochromatography (IE-CEC) with strong cation-exchange packing (SCX) as stationary phase was investigated. It was observed that the number of theoretical plates for small peptides varied from 240 000 to 460 000/m, and the relative standard deviation for t(0) and the migration time of peptides were less than 0.57% and 0.27%, respectively for ten consecutive runs. Unusually high column efficiency has been explained by the capillary electrophoretic stacking and chromatofocusing phenomena during the injection and separation of positively charged peptides. The sample buffer concentration had a marked effect on the column efficiency and peak area of the retained peptides. The influences of the buffer concentration and pH value as well as the applied voltage on the separation were investigated. It has been shown that the electrostatic interaction between the positively charged peptides and the SCX stationary phase played a very important role in IE-CEC, which provided the different separation selectivity from those in the capillary electrophoresis and reversed-phase liquid chromatography. A fast separation of ten peptides in less than 3.5 min on IE-CEC by adoption of the highly applied voltage was demonstrated. (C) 2000 Elsevier Science B.V. All rights reserved.

Alkaline treatment of the cellulose fiber affecting membrane column behaviour for high-performance immunoaffinity chromatography

The original cellulose fibers and those treated by alkaline solution were both used to prepare the acrylic membranes. The two kinds of membranes were packed into the columns for high-performance immunoaffinity chromatography by the immobilization of protein A on them. It was observed that the alkaline treatment of the cellulose fiber decreased the pressure resistance of the membrane to the mobile phases and greatly increased the accessible volume to the proteins, but affected the adsorption capacity of human IgG on the protein A membrane columns less. There is little difference between those two kinds of membranes on the adsorption capacities of HIgG, which means that the alkaline treatment of the cellulose fiber only significantly changes the void volume inter-membrane, and the porosity and surface area of membrane less. Alkaline treatment of the cellulose fiber reduced the membrane-column efficiency significantly. Some typical examples for the immunoaffinity analysis of IgG from human and dog plasma on the protein A membrane columns are illustrated. Copyright (C) 2000 John Wiley & Sons, Ltd.

Preparation and characterization of palladium-based composite membranes by electroless plating and magnetron sputtering

Pd and Pd-Ag (24 wt.%) alloy composite membrane were prepared by electroless plating and magnetron sputtering, respectively. The membranes were characterized by scanning electron microscopy (SEM) and H-2 permeation measurement. Commercial microfiltration ceramic membrane were coated with gamma-Al2O3-based layer by the sol-gel method and used as substrate of Pd and Pd-Ag alloy film. Both the as-prepared membranes were shown: to be He gas-tight at room temperature with a thickness of <1 mu m. Permeation results showed that H-2 permeation through these composite membranes is mainly dominated by the surface chemistry of H-2 on or/and in the membranes. The membranes exhibited a high permeation rate of H-2 and a H-2/N-2 permselectivity of higher than 60 in the optimized operation conditions. (C) 2000 Elsevier Science B.V. All rights reserved.

Syngas production using an oxygen-permeating membrane reactor with cofeed of methane and carbon dioxide

CH4-CO2-O-2 reforming to syngas in a never Ba0.5Sr0.5Co0.8Fe0.2O3.delta oxygen-permeable membrane reactor using LiLaNiO/gamma-Al2O3 as catalyst was successfully reported. Excellent reaction performance was achieved with around 92% methane conversion efficiency, 95% CO2 conversion rate, and nearly 8.5mL/min.cm(2) oxygen permeation flux. In contrast to the oxygen permeation model with the presence of large concentration of CO2 (under such condition the oxygen permeation flux deteriorates with time), the oxygen permeation flux is really stable under the CH4CO2-O-2 reforming condition.

Synthesis and gas permeation properties of an NaA zeolite membrane

A high quality NaA zeolite membrane, which shows a H-2/n-C4H10 permselectivity of 106, has been synthesized on a seeded alpha-Al2O3 support by a multistage synthesis method.

Composite anode for CO tolerance proton exchange membrane fuel cells

Fuel of proton exchange membrane fuel cells (PEMFC) mostly comes from reformate containing CO. which will poison the fuel cell electrocatalyst. The effect of CO on the performance of PEMFC is studied in this paper. Several electrode structures are investigated for CO containing fuel. The experimental results show that thin-film catalyst electrode has higher specific catalyst activity and traditional electrode structure can stand for CO poisoning to some extent. A composite electrode structure is proposed for improving CO tolerance of PEMFCs. With the same catalyst loading. the new composite electrode has improved cell performance than traditional electrode with PtRu/C electrocatalyst for both pure hydrogen and CO/H-2. The EDX test of composite anode is also performed in this paper, the effective catalyst distribution is found in the composite anode. (C) 2002 Elsevier Science B.V. All rights reserved.

Partial oxidation of methane to syngas in tubular oxygen-permeable reactor

A dense Ba0.5Sr0.5Co0.8Fe0.2O3-delta membrane tube was prepared by the extruding method. Furthermore, a membrane reactor with this tubular membrane was successfully applied to partial oxidation of methane (POM) reaction, in which the separation of oxygen from air and the partial oxidation of methane are integrated in one process. At 875degreesC, 94% of methane conversion, 98% of CO selectivity, 95% of H-2 selectivity, and as high as 8.8 mL/(min (.) cm(2)) of oxygen flux were obtained. In POM reaction condition. the membrane tube shows a very good stability.

Protein A tangential flow affinity membrane cartridge for extracorporeal immunoadsorption therapy

Tangential flow affinity membrane cartridge (TFAMC) fs a new model of immunoadsorption therapy for hemoperfusion. Recombinant Protein A was immobilized on the membrane cartridge through Schiff base formation for extracorporeal IgG and immune complex removal from blood. Flow characteristics, immunoadsorption capacity and biocompatibility of protein A TFAMC were studied. The results showed that the pressure drop increased with the increasing flow rate of water, plasma and blood, demonstrating reliable strength of membrane at high now rare. The adsorption capacities of protein A TFAMC for IgG from human plasma and blood were measured. The cartridge with 139 mg protein A immobilized on the matrix (6 mg protein A/g dry matrix) adsorbed 553 mg IgG (23.8 mg IgG/g dry matrix) from human plasma and 499.4 mg IgG (21.5 mg IgG/g dry matrix) from human blood, respectively. The circulation time had a major influence on IgG adsorption capacity, but the flow rate had little influence. Experiments in vitro and in vivo confirmed that protein A TFAMC mainly adsorbed Ige and Little of other plasma proteins, and that blood cell damage was negligible. The extracorporeal circulation system is safe and reliable. Copyright (C) 1999 John Wiley & Sons, Ltd.

Theoretical study of the separation mechanism of ionizable compounds in capillary electrochromatography

The migration mechanism of ionizable compounds in capillary electrochromatography (CEC) is more complicated than in high performance liquid chromatography (HPLC) due to the involvement of electrophoresis and the second chemical equilibrium. The separation mechanism of ionizable compounds in CEC has been studied theoretically. The electrochromatographic capacity factors of ions (k *) in CEC and in the pressurized CEC are derived by phenomenological approach. The influence of pH, voltage, pressure on k* is discussed. in addition, the k * of weak acid and weak base are derived based on acid-base equilibrium and the influence of pH on k * is studied theoretically.