Alumina liquid chromatography

Liquid chromatography is a separation technique based on the selective adsorption on a solid, siiica or alumina for example, or a mixture of the two, of the different components of a liquid mixture. 

The stationary phase matrices used in classic column chromatography are spongy materials whose compress-ibihty hmits flow of the mobile phase. High-pressure liquid chromatography (HPLC) employs incompressible silica or alumina microbeads as the stationary phase and pressures of up to a few thousand psi. Incompressible matrices permit both high flow rates and enhanced resolution. HPLC can resolve complex mixtures of Upids or peptides whose properties differ only slightly. Reversed-phase HPLC exploits a hydrophobic stationary phase of... 

This technique is based on the same separation mechanisms as found in liquid chromatography (LC). In LC, the solubility and the functional group interaction of sample, sorbent, and solvent are optimized to effect separation. In SPE, these interactions are optimized to effect retention or elution. Polar stationary phases, such as silica gel, Florisil and alumina, retain compounds with polar functional group (e.g., phenols, humic acids, and amines). A nonpolar organic solvent (e.g. hexane, dichloromethane) is used to remove nonpolar inferences where the target analyte is a polar compound. Conversely, the same nonpolar solvent may be used to elute a nonpolar analyte, leaving polar inferences adsorbed on the column. 

Ethylenethiourea (ETU) is a toxic decomposition product/metabolite of alky-lenebis(dithiocarbamates). This compound could be generated during processing of treated crops at elevated temperature. Different chromatographic methods to determine the residue levels of ETU have been published. After extraction with methanol, clean-up on a Gas-Chrom S/alumina column and derivatization (alkylation) with bro-mobutane, ETU residues can be determined by GC with a flame photometric detector in the sulfur mode. Alternatively, ETU residues can also be determined by an HPLC method with UV detection at 240 nm or by liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/tandem mass spectrometry (LC/MS/MS) (molecular ion m/z 103). ... 

Sediment Soxhlet extraction clean-up by liquid-liquid partition, alumina column chromatography GC/NPD 81-97 Muiretal. 1981... 

Benzene chemisorption on platinum-alumina in the range 26°-470°C has been measured in a flow system by Pitkethly and Goble (7). A small dose of benzene was injected into a stream of inert carrier gas and transported to the reactor the effluent was then sampled repeatedly and analyzed by gas-liquid chromatography. Information concerning the adsorption and desorption of benzene was obtained from the shape of the subsequent benzene concentration versus time curves. Evidence was obtained for four types of adsorption of benzene ... 

Liquid chromatography (LC) activated alumina applications, 2 400 adsorption, 1 610-611 of ascorbic acid, 25 760 basic principles, 4 603-606 classification of solvents for, 23 87... 

Liquid chromatography 200-400 mesh silica and alumina Organic solvents... 

Beck and Brink [28] have described a sensitive method for the routine assay of cobalamins in activated sewage sludge. The method involves extraction with benzyl alcohol, removal of interfering substances using a combination of gel filtration and chromatography on alumina, concentration of the extract by lyophilization, and direct determination of total cobalamin by high-speed liquid chromatography, in comparison with cobalamin standards. 

Stationary phase materials are synthesized from different raw materials. Those stationary phase materials synthesized from inorganic materials, such as silica and alumina, are physically strong but chemically unstable. Conversely, stationary phase materials synthesized from organic materials, such as polystyrene or poly(vinyl alcohol), are chemically stable but physically weaker. Improvements in the chemical stability of inorganic stationary phase materials and in the physical strength of organic stationary phase materials are required the marketed products do not have both and have to be used under restricted conditions in liquid chromatography. 

Example 2 Chromatography of nitroaniline isomers. The elution order of the nitroaniline isomers was ortho, meta, and para in normal-phase liquid chromatography using H-butanol-w-hexane mixtures as the eluent, when the stationary phase material was either silica gel, alumina, an ion-exchanger, polystyrene gel, or octadecyl-bonded silica gel. The results indicate that the separation of these compounds can be performed on a range of different types of stationary phase materials if the correct eluent is selected. The best separation will be achieved by the right combination of stationary phase material and eluent.68... 

Figure 4.19 Solvent strength of combination of n-pentane and more polar solvents in normal-phase liquid chromatography using alumina. Symbols. A, methyl acetate, 0> acetone, , chloroform, and O, benzene.

Normal phase (NP) was the original mode of high-performance liquid chromatography (HPLC) reported. This uses a polar stationary phase (e.g. sihca, alumina) and non-polar mobile phase. It can also be referred to as adsorption... 

LIQUID CHROMATOGRAPHY ON SILICA AND ALUMINA AS STATIONARY PHASES... 

A Perkin-Elmer Model 21 infrared spectrophotometer was used to detect and to estimate the hydroxylic and carbonyl functions in the oxidized product mixtures. The organic hydroperoxide and peroxide functional groups in the product mixtures were determined by an iodine liberation and titration procedure (11). In order to get reproducible results, it is necessary to pretreat the olefins with about 10 weight % activated silica or alumina for several hours with agitation to remove adventitious peroxides and impurities. Sodium bisulfite solution rapidly destroys hydroperoxides but does not destroy peroxides completely. The hydroperoxides and peroxides decomposed extensively during attempted distillation at about 1 mm. of Hg partial vacuum. We had some success in concentration by liquid chromatography over silica gel the unconverted olefins are eluted with n-hexanes, and a hydroperoxide-peroxide... 

Methods. Adsorption isotherms were run at constant feed molar ratio of C oS0 /Ci3eS0.. The feed solutions had a pH of 4.25 and a NaCl concentration of 0.15 M. Ten ml of feed solution was added to 0.5 g alumina in a screw top centrifuge tube and centrifuged at 700 RPM for 45 minutes at room temperature. The tube was then placed in a water bath at 30°C for four days, the liquid decanted from the mineral and analyzed. The surfactant concentrations were analyzed using high performance liquid chromatography with a conductivity detector. The solution pH after equilibration was determined using pH electrodes. The equilibrium pH increased to 6.8 at equilibrium because the PZC of alumina is approximately 9. 

Octadecanol was recrystallized from hexane after fractionation by vacuum distillation, and its purity was checked by gas-liquid chromatography. Dodecylammonium chloride was recrystallized from a mixture of ethanol and water, and its purity was confirmed by the fact that it had no minimum near the critical micelle concentration on the surface tension vs concentration curve. Hexane was distilled after passing through an activated alumina column. Water was distilled from alkaline permanganate solution of distilled water after refluxing for one day. The purity of hexane and water was confirmed by the value of the interfacial tension between them. 

Platinum porphyrin complexes can be prepared by reaction with PtCl2(PhCN)2. Purification of the final complex is by medium pressure liquid chromatography on alumina. The strongly phosphorescent platinum(II) porphyrin complexes are efficient sensitizers for stilbene isomerization. The quantum yields for the cis to trans process are greater than unity because of a quantum chain process in which the metalloporphyrin serves both as an energy donor and an acceptor.1110 Picosecond laser spectroscopy has been used to obtain time-resolved excited-state spectra of platinum octaethylporphyrin complexes, and to probe the excited-state energy levels.1111 Tetrabenzoporphyrin complexes have been prepared for platinum in both the divalent and tetravalent oxidation states. The divalent complex shows strong phosphorescence at 745 nm.1112... 

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