Alumina column preparation

Water-Soluble Annatto Extracts Transfer 2 mL or 2 g of sample into a 50-mL separatory funnel, and add sufficient 2 N sulfuric acid to make the solution acidic to pH test paper (pH 1 to 2). Dissolve the red precipitate of norbixin by mixing the solution with 50 mL of toluene. Discard the water layer, and wash the toluene phase with water until it no longer gives an acid reaction. Remove any undissolved norbixin by centrifugation or filtration, and dry the solution over anhydrous sodium sulfate. Transfer 3 to 5 mL of the dry solution to the top of an alumina column prepared as described above. Elute the column with toluene, three 10-mL volumes of dry acetone, and 5 mL of Carr-Price Reagent (see Solutions and Indicators) added to the top of the column. The orange-red band of norbixin immediately turns blue-green. 

Cholestenone. Place a mixture of 1 0 g. of purified cholesterol and 0-2 g. of cupric oxide in a test-tube clamped securely at the top, add a fragment of Dry Ice in order to displace the air by carbon dioxide, and insert a plug of cotton wool in the mouth of the tube. Heat in a metal bath at 300-315° for 15 minutes and allow to cool rotate the test-tube occasionally in order to spread the melt on the sides. Warm with a few ml. of benzene and pour the black suspension directly into the top of a previously prepared chromatographic column (1) rinse the test-tube with a little more benzene and pour the rinsings into the column. With the aid of shght suction (> 3-4 cm. of mercury), draw the solution into the alumina column stir the top 0 -5 cm. or so with a stout copper wire to... 

Activity III alumina is prepared by adding 6% (w/w) of water to neutral alumina of activity grade I. The submitters used a 50x3 cm. glass column for the chromatography. 

Prepare an alumina column as described in Section 3. Dissolve the residue prepared in Section 6.2.1 in 3 mL of n-hexane-ethyl acetate (10 1, v/v) and transfer the solution to the column. Rinse the flask twice with 5 mL of the same solvent system and transfer these solutions into the column. Allow the solution to percolate through the column and discard the eluate. Add 160mL of n-hexane-ethyl acetate (10 1, v/v) to the column. Discard the first 40 mL of eluate and collect the second 120 mL of eluate in a 300-mL round-bottom flask. Evaporate the eluate to dryness under reduced pressure. 

Alumina column cleanup. Prepare an alumina column by placing a glass-wool plug in the bottom of a glass chromatography column. Slurry 10 g of alumina with hexane-ethyl acetate (10 1, v/v), and pour the slurry into the column. Rinse the walls of the column with hexane-ethyl acetate (10 1, v/v), and add approximately 2g of sodium sulfate to the top of the alumina column. Drain the solvent to the top of the sodium sulfate layer. 

In this preparation the nitroso compound may be added in solution form to a solution to the amine at low temperature. The solvent may be a suitable mixture of acetic acid and ethanol as well as acetic acid alone. The product may also be extracted from a reaction mixture diluted with water by use of ether [32]. Purification of the final product may be carried out by chromatography on an alumina column. 

The normally prepared azo compounds are, as expected, predominantly in the trans form. However, on chromatographing typical azo compounds on an alumina column, a small, extraneous band had been observed which was subsequently identified as a small amount of the cis isomer. 

A number of macrocycles containing only one phosphorus atom have been prepared, and they are usually referred to as phosphorus-containing crown ethers rather than as P macrocycles. The 18-crown, or [18]anePOs, was prepared by van Zon (equation 28).82 This cyclic phosphine is stable in air, even in solution (cf. Ph3P). However, when the non-macrocyclic substituent is Bul the phosphorus is oxidized in solution by air in the presence of alumina. This unwelcome discovery was made by van Zon when purifying the material by chromatography on an alumina column. 

Microparticulate alumina specially prepared for HPLC is available commercially and facilitates the isocratic separation of all-tram-/3-carotcnc from its lower potency cis isomers. Using an alumina column and a mobile phase of isooctane containing 0.5% stabilized tetrahydrofu-ran (161), the cis isomers of /3-carotene are eluted before the all-tram- isomer to form a single composite peak in the chromatogram. a-Carotcnc coelutes with the cis isomers of /3-carotene and therefore cannot be accurately quantified. y-Carotcnc, /3-cryptoxanthin, and canthaxanthin are not eluted. 

Adsorption column preparation and loading. In order to obtain satisfactory results, the tube must be uniformly packed with the adsorbent uneven distribution may lead to the formation of cracks and channels and to considerable distortion of adsorption band shapes. If there is any doubt concerning the uniformity of particle size of the adsorbent powder it should be sifted before use to remove the larger particles fines are removed from the adsorbent using a sedimentation procedure immediately prior to column packing. In this the alumina or silica gel adsorbent is stirred into between five to ten times its volume of the selected solvent or solvent system, allowed to settle for five minutes and the supernatant liquor decanted off the procedure is repeated until the supernatant liquid is clear. 

The sample preparation methodology for the determination of TCDD at these low levels is an active area of development as indicated by the improved procedure reported here and used to analyze the milk for the NIEHS study. It uses reagent modified adsorbants, a higher efficiency basic alumina column than previously (19) and a new degree of separation, reverse phase HPLC as an integral part of the procedure. All of these are directed towards improving the specificity of the sample preparation for 2,3,7,8-TCDD. Increased specificity is needed since the lowest detection limit achievable in all previous studies of TCDD in environmental samples has been dictated by the presence of other substances in the samples which have not been removed by the sample preparation. 

A similar strategy has been used to synthesize the 1,4-diazepine skeleton, starting from 4-azidopyridines. The preparative-scale irradiation (400 W, high-pressure Hg lamp, Pyrex filter) of azides 148 in MeOH/dioxane (1 1) containing NaOMe resulted in the formation of 5-methoxy-6H-l,4-diazepines 149 as the more stable tautomer (Scheme 12.38) [94]. It should be noted that compounds 149 are found to be susceptible to decomposition on silica or alumina columns hence, care must be taken in their purification and storage. 

The fullerenes, Cgo and C70, are produced in the laboratory by the contact arc-evaporation of 6 mm graphite rods (e.g. Johnson Matthey, spectroscopic grade) in 100 torr of helium in a water-cooled stainless steel chamber described previously [5]. The soluble material in the soot produced from the arc-evaporation is extracted with toluene using a Soxhlet apparatus. The pure fullerenes are obtained by chromatography on neutral alumina columns using hexanes as the eluant, or by the use of a simple filtration technique using charcoal-silica as the stationary phase and toluene as the eluant [5]. The fullerenes so prepared are characterized by UV/Vis spectroscopy and other techniques. FT-IR spectra of vacuum deposited fullerene films on KBr crystals also provide a means of characterization, just as do Raman spectra of films deposited on a silicon crystal. Ultraviolet and X-ray photoelectron spectra of fullerene films on... 

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