Modeling liquid-liquid interface level in a horizontal three-phase separator with a bucket and weir

The flow behavior in a three-phase separator with a bucket and weir was analyzed, and a theoretical equation for calculating the liquid-liquid interface level (H_H) in gravity separation zone was derived. The analysis indicates that the H_H increases as the flow rate and the density ratio of heavy to light liquid increase, and decreases linearly with increasing height difference between heavy and light liquid overflow weirs. The calculated H_H under different operating conditions is in good agreement with the experimental. With the proposed equation, the thicknesses of heavy and light liquid layers can be calculated, and then the minimum lengths of two phase layers required for separation can be determined separately. From the minimum lengths it can be clearly indicated that the governing step of liquid-liquid separation is in heavy or light liquid layers, hence the sizing of the separator can be optimized.     

Chiral silica-based monoliths in chromatography and capillary electrochromatography

Chiral-modified silica-based monoliths have become well-established stationary phases for both high performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). The silica-based monoliths were fabricated either in situ in the capillaries for nano-HPLC and CEC or in a mould for “conventional” HPLC. The present review summarizes the chiral modification of silica monoliths and the recent development in the field of enantioselective separations by nano-HPLC and CEC.     

Profiling of phospholipids in lipoproteins by multiplexed hollow fiber flow field-flow fractionation and nanoflow liquid chromatography–tandem mass spectrometry

This study describes a coupled analytical method to carry out the systematic profiling of phospholipids (PLs) in high-density lipoproteins (HDL) and low-density lipoproteins (LDL) from human blood plasma. HDL and LDL of healthy human plasma samples were separated by size and collected on a semi-preparative scale using multiplexed hollow fiber flow field-flow fractionation (MxHF5). Phospholipid mixtures contained in the resulting HDL and LDL fractions were analyzed by shotgun nanoflow liquid chromatography–tandem mass spectrometry (nLC–ESI-MS–MS). We utilized a dual scan method for the separation and simultaneous characterization of complicated PL mixtures by nLC–ESI-MS–MS, such that phosphatidylcholine (PC) and phosphatidylethanolamine (PE) molecules were detected in positive ion mode in a first LC run. In a second LC run, phosphatidylinositol (PI), phosphatidylglycerol (PG), and phosphatidic acid (PA) were detected in negative ion mode. In this study, a total of 56 PLs from HDL and 52 PLs from LDL particles were characterized by their molecular structures from data dependent collision-induced dissociation (CID) experiments, and their relative abundances were compared.     

Effect of particulate filler on cell size in membranes formed via liquid–liquid thermally induced phase separation

This paper discusses the effects of adding particulate filler to a system undergoing liquid–liquid thermally induced phase separation (L–L TIPS). While much is known about the growth of droplets in L–L TIPS, little is known about the effect particular fillers have on droplet growth and the final cell size in the resulting microporous membranes. In this work, zeolite particles are shown to have a significant effect on the final cell size of these microporous membranes, the extent of which depends on the particle loading and processing conditions used to form the membrane. Two polymer–diluent–zeolite systems are reported: isotactic polypropylene–diphenyl ether and poly(methyl methacrylate)–cyclohexanol, both with zeolite 4A particles.     

冠醚B15C5萃取分离锂同位素的阴离子效应

本文研究了B15C5冠醚萃取锂盐时,不同阴离子对体系的同位素分离效应的影响。结果表明,阴离子在冠醚萃取过程中不仅对萃取络合物的稳定性有显著影响,而且阴离子半径及软度越大时,萃取体系的锂同位素分离系数(α_(LI))也越大。     

Phase separation of poly(γ-benzyl L-glutamate) to liquid crystal and isotropic solution in various helicogenic solvents

Solvent effects on the phase separation of poly(-benzyl L-glutamate) to liquid crystal and isotropic solution have been observed in various helicogenic solvents. The temperature-composition phase diagrams have been determined for each solution. The critical concentrations, ₂ ^* , at which the phase separation occours have been compared in various solvents. In dimethylformamide in which the polymer is molecularly dispersed, the observed ₂ ^* value has agreed with that calculated by Flory's theory. In some solvents in which the polymer aggregates in a head-to-tail mode such as chloroform, the observed ₂ ^* values have been considerably small. It is assumed that the polymer aggregates behave as longer particles than the original particles. In dioxane in which the polymer aggregates highly both in a head-to-tail and a side-by-side modes, the ₂ ^* value has been a little larger than that in chloroform. In this case the relationship between the aggregation and the liquid crystal formation is so complicated that further investigation is necessary. In aromatic solvents such asm-cresol that dissolves the polymer almost molecularly, the ₂ ^* is smaller than that in dimethylformamide. Therefore, the intermolecular interactions between the phenyl groups in the side groups of the polymer and those in solvent molecules must be considered.The author is grateful to Mr. K. Sano and Mr. M. Watanabe for their observation of the liquid crystal formation.     

Reverse-phase high-performance liquid chromatography of virus proteins and other hydrophobic proteins

Summary So far most solvents generally used in reverse phase chromatography (RPC) for separation of peptides and water soluble polypeptides could not be utilized for hydrophobic proteins such as membrane proteins and structural polypeptides of viruses due to their insufficient solubility. But we have introduced a new RP-HPLC solvent system which was very useful in our studies on poliovirus polypeptides. Formic acid in high concentration is an extremely potent solvent for proteins, particularly those that are hydrophobic. Preliminary estimates are made of the concentration of formic acid which is required to completely dissolve hydrophobic proteins. For example, solubilization of structural polypeptides of poliovirus which are absolutely water insoluble requires 60% formic acid. Therefore, we used a proportion of 60% formic acid in all solvents for reversed phase chromatography and applied propanol-2 or acetonitrile as the organic modifiers for gradient elution. Using this mobile phase all four poliovirus polypeptides of three serological types were obtained in high purity by this rapid procedure. In each case, polypeptides were quantitatively eluted independent of the amount of protein (1–1000 μg) injected onto the columns. The solvents used were volatile and easily removed in a short evaporation step. Therefore this solvent system is suited for analytical and for micropreparative separation of proteins for chemical, biochemical and immunological studies. Rechromatography and electrophoresis in SDS-polyacrylamide gels of the separated polypeptides demonstrated that this solvent system with its high proportion of formic acid did not alter their primary structure. There may have been major changes in secondary and tertiary structure. In contrast, alterations of the elution characteristics were observed after reduction of disulfide bridges and several modifications of proteins. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Chromatographic separation of some metal ions on NTA-impregnated thin-layer plates

Summary NTA (nitrilo triacetic acid) has been used as an impregnating agent for an efficient TLC separation of twelve metal ions, using a mixture of 5% aq ammonia, ethanol acetone and acetic acid as the solvent system and dithizone (0.5% in chloroform) for visualization.     

Practical limitations of capillary gas chromatography

Glass capillary gas chromatography is a high resolution separation method which allows the qualitative and quantitative analysis of even complex mixtures, which may contain many components–also isomeric–in a wide range of volatilities, polarities and concentrations. The principal limitation of gas chromatographic application is given by an insufficient volatility of the species to be separated. Elevated temperatures have to be applied if the application range is to be extended and to achieve steep peak profiles, i.e. low detection limits at high resolution. The use of elevated temperatures is limited, of course, by the temperature stability of both the solvent (stationary liquid and support) and the solutes. The problems of trace analysis for low volatility compounds at high resolution and its limitational parameters regarding sampling, separation and detection are discussed. The applicability of glass capillary columns in this field is influenced by the following parameters: tailing behaviour; irreversible adsorption of polar and decomposition of unstable solutes; thermal stability of stationary liquid (including the support deactivation); separation efficiency and sample capacity (film thickness). Multidimensional gas chromatography using capillary columns coupled either with a packed or another capilllary column for preseparations may be applied with advantage in the analysis of complex mixtures.