Alumina chromatographic column

Tetrasulfur tetranitride, as prepared by the above procedures, usually has a melting point of 178 to 179°. However, by repeated recrystallization from benzene or by purification on an alumina chromatographic column, S4N4 with a melting point as high as 187 to 187.5° has been obtained. It has been observed that the sensitivity of S4N4 toward both shock and temperature increases with its purity. Even the... 

This type of analysis requires several chromatographic columns and detectors. Hydrocarbons are measured with the aid of a flame ionization detector FID, while the other gases are analyzed using a katharometer. A large number of combinations of columns is possible considering the commutations between columns and, potentially, backflushing of the carrier gas. As an example, the hydrocarbons can be separated by a column packed with silicone or alumina while O2, N2 and CO will require a molecular sieve column. H2S is a special case because this gas is fixed irreversibly on a number of chromatographic supports. Its separation can be achieved on certain kinds of supports such as Porapak which are styrene-divinylbenzene copolymers. This type of phase is also used to analyze CO2 and water. 

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... 

A chromatographic column filled in three sections with ground sugar, chalk, and alumina. When a petroleum extract of spinach leaves is run onto the top of the column, ihe extract spreads down the column, but not uniformly bands of green chlorophylls stop near the top. yellow xanthophyll further down, and red carotene near the bottom. 

When the uptake of hydrogen ceased, the catalyst was filtered and the solution was evaporated to dryness under vacuum. The residue was dissolved in a mixture of benzene-hexane, transferred to a chromatographic column with neutral alumina and the product was eluted with mixtures of benzene-hexane, gradually increasing the proportion of benzene in the mixture. Crystallization of the eluates from acetone-hexane yielded the propionate of 2a-methyldihydrotestosterone. 

In a dry, 1-1., two-necked flask, equipped with a mechanical stirrer and a reflux condenser fitted with a drying tube, are placed 17.8 g. (0.100 mole) of anthracene (Note 1), 27.2 g. (0.202 mole) of anhydrous cupric chloride (Note 2), and 500 ml. of carbon tetrachloride (Note 3). The reaction mixture is stirred and heated under reflux for 18-24 hours. The brown cupric chloride is gradually converted to white cuprous chloride, and hydrogen chloride is gradually evolved. At the end of the reaction the cuprous chloride is removed by filtration, and the carbon tetrachloride solution is passed through a 35-mm. chromatographic column filled with 200 g. of alumina (Note 4). The column is eluted with 400 ml. of carbon tetrachloride. The combined eluates are evaporated to dryness to give 19-21 g. (89-99%) of 9-chloroanthracene as a lemon-yellow solid, m.p. 102-104° (Note 5). Crystallization of the product from petroleum ether... 

In LC-ICP-MS, samples are separated on a chromatographic column, which may be a simple silica or alumina column with a relatively simple eluent. As the components elute from the column, they enter the ICP and the identity of the elements present and their concentration are determined based on the wavelengths of light (identity) and intensity of light (quantification) they emit. The exhaust from the ICP then enters the mass spectrometer, where the metals and their isotopic composition are determined based on their characteristic m/z ratios. The metals are thus identified and verified by two methods, ICP and MS [15]. 

B. 2,2-(Trimethylenedithio)cyclohexanone. A solution of 3.02 g. (0.02 mole) of freshly distilled 1-pyrrolidinocyclohexene, 8.32 g. (0.02 mole) of trimethylene dithiotosylate4 (Note 2), and 5 ml. of triethylamine (Note 3) in 40 ml. of anhydrous acetonitrile (Note 4), is refluxed for 12 hours in a 100-ml., round-bottom flask under a nitrogen atmosphere. The solvent is removed under reduced pressure on a rotary evaporator, and the residue is treated with 100 ml. of aqueous 0.1 N hydrochloric acid for 30 minutes at 50° (Note 5). The mixture is cooled to ambient temperature and extracted with three 50-ml. portions of ether. The combined ether extracts are washed with aqueous 10% potassium bicarbonate solution (Note 6) until the aqueous layer remains basic to litmus, and then with saturated sodium chloride solution. The ethereal solution is dried over anhydrous sodium sulfate, filtered, and concentrated on a rotary evaporator. The resulting oily residue is diluted with 1 ml. of benzene and then with 3 ml. of cyclohexane. The solution is poured into a chromatographic column (13 x 2.5 cm.), prepared with 50 g. of alumina (Note 7) and a 3 1 mixture of cyclohexane and benzene. With this solvent system, the desired product moves with the solvent front, and the first 250 ml. of eluent contains 95% of the total product. Elution with a further 175 ml. of solvent removes the remainder. The combined fractions are evaporated, and the pale yellow, oily residue crystallizes readily on standing. Recrystallization of this material from pentane gives 1.82 g. of white crystalline 2,2-(trimethylenedithio)cyclo-hexanone, m.p. 52-55° (45% yield) (Note 8). 

Japenga et al. [56] determined polychlorinated biphenyls and chlorinated insecticides in River Elbe estuary sediments by a procedure in which the sediments were pretreated with acetic acid, mixed with silica and Soxhlet-extracted with benzene/hexane. Humic material and elemental sulphur were removed by passing the extract through a chromatographic column containing basic alumina, on which sodium sulphite and sodium hydroxide were adsorbed. Silica fractionation was followed by gas chromatography to analyse chlorinated pesticides, polychlorinated biphenyls and polyaromatic hydrocarbons. Recovery experiments with standard solutions gave recoveries of 90-102%. 

The crude solid is purified by dissolving it in 50 ml. of petroleum ether (b.p. 40-60°) and introducing it on a short alumina column (IS g.j Brockmann Activity 1 or an equivalent chromatographic alumina). The column is then eluted with 300 ml. of a 1 9 mixture of ether-petroleum ether (b.p. 40-60°). Concentration of the eluate leaves a solid which is recrystallized from aqueous ethanol to give 1.4-1.6 g. (70-80%) of diphenyldiacetylene as large colorless needles, m.p. 87-88° (Note 10). 

Dimethylsulfoxide is purified by filtration through a 2 x 25 cm chromatographic column filled with alumina (activated grade I, neutral, 150 mesh), under a nitrogen atmosphere. This procedure of purification of the solvent is crucial to obtain the indicated yield, since on use of distilled or commercially available anhydrous dimethylsulfoxide, extensive decomposition takes place. 

Liquid Chromatography. The distillates were separated on a dual-packed (silica gel-alumina gel) chromatographic column according to... 

Catalysts pre-treatment (calcination and reduction) was performed in the same testing system or in a parallel automatic activation system prior to reaction test Calcination is carried out at 600 °C under airflow for 8 h and reduction at 250 °C for 2 h under hydrogen flow. Catalytic tests were carried out at 30 bar total pressure, temperature range 200-240°C, and 2.26h-1 WHSV, H2/hydrocarbons molar ratio of 2.93. Each fixed bed microreactor contained 500 mg of catalyst (particle size 0.4—0.6 mm, for which there are no internal diffusion limitations). Reaction products distribution are analysed using a gas chromatograph (Varian 3380GC) equipped with a Plot Alumina capillary column. 

The gasoline feed was cracked over a fixed bed (4.69g) of the relevant catalyst and liquid and gaseous products were collected in conventional MAT receivers. Gaseous products were analysed on a dual-column Hewlett Packard 5890 gas chromatograph where hydrogen and nitrogen were quantified on a 13X column linked to the TCD detector. Individual hydrocarbons in the number range Cl - C7 were quantified on a 50m alumina-PIOT column carbon linked to an FID detector. The liquid fraction from each test was analysed directly on a FIONA analyser supplied by Analytical Control BV. 

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