Low pressure chromatography

Proteins precipitation Low pressure cationic exchange chromatography Low pressure cationic exchange chromatography TCA 7% 4 Dowex 50-X2 Amberlite IR-H 120 Yokotsuka et al. (1975) Usseglio-Tomasset and Bosia (1990)... 

Ion-Exchange Chromatography. Low pressure GPC has almost universally replaced low pressure ion-exchange chromatography. However, the basic principles, which in most cases do not reflect true ion-exchange, have been refined and incorporated into HPLC. 

Ion Exchange Resins - Spectra/Gel Ion Exchange resins are ion exchange media for use in low-pressure liquid chromatography. They are based on a polystyrene/divinylbenzene support and are available for both anion and cation exchange applications. This site will give you a reasonable... 

With 2537 k-Light. 1 g (140) in 140 ml anhydrous dioxane is irradiated for 20 hr at room temperature with a Hanau NK 6/20 low-pressure mercury lamp placed in a central water-cooled quartz finger. 0.19 g of (141) crystallize from the crude reaction mixture as described above. Chromatography of the residual material on silica gel with benzene-ethyl acetate (4 1) gives 0.29 g of B-nortestosterone acetate [(142) 28.5 %] and starting material (140). 

T. L. Chester and J. D. Pinkston, Pressure-regulating fluid interface and phase behavior considerations in the coupling of packed-column supercritical fluid chromatography with low-pressure detectors , ]. Chromatogr. 807 265-273 (1998). 

Flash chromatography is widely employed for the purification of crude products obtained by synthesis at a research laboratory scale (several grams) or isolated as extracts from natural products or fermentations. The solid support is based on silica gel, and the mobile phase is usually a mixture of a hydrocarbon, such as hexane or heptane, with an organic modifier, e.g. ethyl acetate, driven by low pressure air. (Recently the comparison of flash chromatography with countercurrent chromatography (CCC), a technique particularly adapted to preparative purposes, has been studied for the separation of nonchiral compounds [90].)... 

An ice-cold solution of a 3-oxa-6-azatricvclo[3.2.0.02,4]hept-6-ene 1 (0.5-1.0 mmol) in MeCN (200 mL) was irradiated with a 30-W low-pressure Hg lamp for 10-125 min. The solvent was removed under reduced pressure and the residue was treated with active charcoal and hexane/i-Pr20. The mixture was filtered and the filtrate was evaporated under reduced pressure to leave the almost pure 1,4-oxazepines as orange oils, which showed vmal (neat) — 1660-1650 cm-L The products decomposed on attempted chromatography. 

A solution of phenol (188 mg, 2 mmol) and benzonitrile (2.06 g, 20 mmol) in McCN (20 mL) was degassed by bubbling nitrogen through it and irradiated with a 16-W low-pressure mercury arc lamp (Applied Photophysics Ltd, APQ40) for 24h. The crude product was separated by flash chromatography (EtOAc/ petroleum ether 1 5) to give yellow crystals yield 79 mg (20%) mp 53-55 C. 

DEAE-cellulose chromatography. The 50% ethanol solution is poured onto a column of DEAE cellulose (2.6 x 10 cm), and F adsorbed at the top is eluted with 20 mM Tris buffer, pH 7.5, containing 0.2 M NaCl. A low pressure of argon gas is applied to accelerate the flow rate. The fractions containing F are combined, concentrated, and desalted using ethanol. 

Totally porous particles of relatively large particle sizes were widely used in low pressure liquid chromatography for many years. These column packings had good sample capacity but only limited efficiency accompanied by long separation times, due to the large size and unfavorable size distribution of the particles and the presence of relatively deep pores within the particles through whick sample molecules diffused in and out of very slowly. 

HPLC as a purification technique and as a tool for process monitoring has become increasingly attractive and will find many new applications in the future. Low pressure LC, probe LC, and micro-LC are techniques important to the future of process chromatography. Specialized detectors and multidimensional chromatographic approaches are also of increasing use. Additional literature is available.22 33-36... 

Ahrer, W. and Buchberger, W., Analysis of low-molecular-mass inorganic and organic anions by ion chromatography-atmospheric pressure ionization mass spectrometry, /. Chromatogr A, 854, 275, 1999. 

Principles and Characteristics SFC-MS is a sensitive coupled technique that can be selective or universal it was first mentioned in 1978 [396]. Further developments are given in Table 7.36. It is used in an on-line mode with open cell gas-phase interfaces, where the mobile phase is decompressed to low pressures. SFC presents a number of features which allow for easier coupling with MS than other chromatographies. In practice, however, SFC-MS coupling did not turn out to be as easy as expected, a fact which can be ascribed to the problems met in the adiabatic expansion of the mobile phase and the effects of pressure gradients in the ion... 

LAC(CC) Liquid adsorption chromatography LPGC Low-pressure gas chromatography... 

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