Aluminium oxide chromatography

Alkaline hydrolysis, 282 Alkanes, 152,324 Alkanediols and their esters, 143 Alk-1-enyldiacylglycerols, 134 Alkoxyhydroperoxide, 463 Alkyd paints, 245 Alkyldiacylglycerols, 134 Alkylglycerols, MS, 436 Alkylsulphates, 36 Allenic acids, 13, 53 Allylic bromination, 466 Almond oil, 3,51,97 Aluminium alkoxide derivatives, 246 Aluminium oxide, chromatography,... 

The reagent, which can also be employed to impregnate the layer before chromatography, is best suited for silica gel layers [4] it can, however, also be employed on aluminium oxide, kieselguhr. Si 50000, cellulose and polyamide layers [4]. 

The starting material for the above step may be prepared as follows 5 g (0.016 mol) of N -(p-methoxyphenyl)-p-chlorobenzhydrazide hydrochloride and 4.75 g (0.018 mol) of benzyl levulinoyloxyacetate were heated In 25 ml of glacial acetic acid for 3 hours at 80°C. The solvent was then evaporated off under vacuum. The residue was taken up in chloroform and the solution was washed neutral by shaking with sodium bicarbonate solution and thereafter with water. After drying the chloroform solution, this was subjected to chromatography on aluminium oxide, the eluate was concentrated by evaporation and the viscous oil remaining as residue was crystallized by adding ether. The compound melted at 94°-95 t. The yield was 4.1 g which corresponds to 50.7% of the theoretical yield. 

Table 2.1 Summary of some examples of detection after merely heating aluminium oxide layers (Types 150/T or 60/E) after chromatography.

In addition the role played by the sorbent on which the chromatography is carried out must not be neglected. For instance, it is only on aluminium oxide layers and not on silica gel that it is possible to detect caffeine and codeine by exposure to chlorine gas and treatment with potassium iodide — ben2idine [37]. The detection limits can also depend on the sorbent used. The detection limit is also a function of the h/ f value. The concentration of substance per chromatogram zone is greater when the migration distance is short than it is for components with high h/ f values. Hence, compounds with low h/ f values are more sensitively detected. 

Heise and Litz [26] investigated the extraction behaviour of surfactants (LAS, NPEO and cationics) from sand comparing Soxhlet extraction, accelerated solvent extraction (ASE) and microwave-assisted extraction. Fractionation of the three surfactant types anionic, non-ionic and cationic, was accomplished by column chromatography with aluminium oxide. Soxhlet extraction and ASE of spiked sand with methanol—stored during 7 days prior to extraction—gave similar recoveries for both LAS and NPEO with values between 88 and 116%. Less efficient extraction was achieved by microwave extraction (79% for NPEO). 

Bundt ei al. [1] separated low-boiling petroleum hydrocarbons from the aliphatic, mono-, di- and polyaromatics by column chromatography. This separation was simplified by removal of non volatile polar components using a silica gel-aluminium oxide column. See also Table 6.3. 

Alkaloids of Aconitum confertiflorum Monoacetyltalatisamine.—The tubers of A. confertiflorum (DC.) Voroschilov were extracted with dichloroethane to yield 1.98% of total alkaloids.12 Thin-layer chromatographic analysis indicated that this alkaloid fraction contained at least nine components. Two of the bases were isolated by column chromatography on aluminium oxide. The first alkaloid was an amorphous base, reported to be a monoacetyltalatisamine (4). Neither structure... 

In paper chromatography we use filter paper, marketed for this purpose. It comes usually in the form of a 2-5 cm-wide tape, from which a strip of the necessary length can easily be cut. The more modern technique of thin layer chromatography (TLC), makes use of thin sheets of aluminium oxide, silica-gel, cellulose or some other material, supported by a metal sheet or a polymer. Chromatographic thin layers can be prepared in the laboratory from commercially available adsorbents. A thick suspension of these is made with water (usually a 2 1 w/w mixture of water adsorbent is made up) and this is then spread on a metal plate with a suitable spreader device. Techniques vary from device to device, and the instructions of the manufacturer should be followed whenever thin layer plates are to be prepared. Ready-made thin layer sheets are also available commercially. These contain the active material spread on a plastic support. Thin-layer chromatographic materials, especially ready-made plates, are much more expensive than chromatographic paper, but normally offer faster and sharper separations than the paper. The procedures described in Section VI.20 can be carried out both on a slow chromatographic paper (e.g. Whatman No. 1) or on a cellulose thin layer (e.g. Whatman cellulose). 

Conventional thin-layer chromatography (TLC) in our experience, known under the name planar chromatography, uses horizontal or vertical glass or Teflon chambers for the development of chromatograms. As stationary phases, commonly known adsorbents or supports based on silica gel, aluminium oxide, magnesium silica, cellulose, and so forth are used particle sizes are about 20 jitm. The migration of the mobile phase is based on the phenomenon of capillary forces. This chromatographic method is described, in detail, in other sections of this volume. 

To 292 mg (1.3 mmol) of a mixture of 1.2.6d/1.2.6e (1 9) dissolved in ether 500 mg of aluminium oxide neutral was added and this heterogenous mixture was stirred for 2 h at room temperature. Filtration and rota-evaporation of the solvent gave an oily raw product which was crystallized at -20 °C from ether/hexane to yield 270 mg (93%) of pure 1.2.6d, mp 48 - 49 °C. All spectroscopic datas were identical with the sample obtained by chromatography of the photoproduct. 

The phosphonium salt was subjected to a Wittig reaction with a dimethylformamide solution of 212 mg (2 mmol) of benzaldehyde and sodium methoxide as a base. The solution was heated at about 80 °C and stirred for 8 h. After cooling, water was added and the mixture extracted with toluene. The combined extracts were washed with water, dried over MgS04 and the solvent evaporated. After column chromatography of the residue on aluminium oxide with CCI4 as the eluant the cw-isomer of 2-styrylbenzo[c]phenanthrene was isolated, whereas the traiw-isomer was obtained after elution with a mixture of hexane and toluene (1 5). The overall yield was 65% (mp cis. 142 - 144 °C, mp trans-. 224 - 226 °C). 

After cooling to room temperature, the crude product was rapidly purified under a nitrogen atmosphere by flash-chromatography over neutral aluminium oxide (petroleum ether/ethyl acetate 90/10) to afford the pure compound as an orange solid (0.27 g, 98% yield). 

The separation of individual QBA is rather difficult, and several methods have been described in the literature (procedures based on different basicity, separation in the form of dihydro derivatives, column chromatography of the free bases, and others) [5,8], none of which seems to be suitable for the isolation of minor QBA Column chromatography of QBA acetates on acidic aluminium oxide has been very effective [30]. This method has been modified for the separation of QBA chlorides [60]. A recent alternative is the use of column chromatography with a non-polar sorbent and an acidic aqueous mobile phase [41]. Many reports of HPLC detection... 

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