Column aluminum oxide

Capillary columns coated with aluminum oxide and molecular sieves can be described as absorption phases [22]. These columns are also known as porous-layer open tubular (PLOT) columns. Aluminum oxide PLOT columns deactivated with potassium chloride have been very effective at the separation of C,.,0 hydrocarbons. 

Typical adsorbents in PLOT columns are, similar to packed columns, aluminum oxide, molecular sieve, and modified cross-linked porous polymers. Aluminum oxide is a very selective stationary phase and it enables the separation of all Ci- to C4-hydro-carbons according to C-number, structure, and degree of saturation. The high surface activity is... 

Reagent grade dichloromethane is dried by passing over a column of aluminum oxide (activity I). 

The checkers used a 30-mm. (I.D.) chromatographic column charged with approximately 250 g. of activated (400° for 12 hours), acid-washed, chromatographic aluminum oxide (Merck and Co., Inc.). 

A mixture of 50 g of betamethasone, 50 cc of dimethylformamide, 50 cc of methyl orthobenzoate and 1.5 g of p-toluenesulfonicacid Is heated for 24 hours on oil bath at 105°C while a slow stream of nitrogen is passed through the mixture and the methanol produced as a byproduct of the reaction is distilled off. After addition of 2 cc of pyridine to neutralize the acid catalyst the solvent and the excess of methyl orthobenzoate are almost completely eliminated under vacuum at moderate temperature. The residue Is chromatographed on a column of 1,500 g of neutral aluminum oxide. By elution with ether-petroleum ether 30 g of a crystalline mixture are obtained consisting of the epimeric mixture of 170 ,21 -methyl orthobenzoates. This mixture is dissolved without further purification, in 600 cc of methanol and 240 cc of methanol and 240 cc of aqueous 2 N oxalic acid are added to the solution. The reaction mixture is heated at 40°-50°C on water bath, then concentrated under vacuum. The residue, crystallized from acetone-ether, gives betamethasone 17-benzoate, MP 225°-231°C. 

A solution of 3.5 g 4-(2,3-epoxypropoxy)carbazole in 50 ml absolute alcohol is mixed with 30 ml isopropylamine and heated for 3 hours under reflux. When the reaction is finished, the reaction mixture is evaporated to dryness. The residue obtained is taken up in methylene chloride and chromatographed over an aluminum oxide column (300 g basic aluminum oxide, activity stage IV eluent methylene chloride). The eluted fractions are evaporated and the residue is dissolved in methanol and acidified with 2N ethereal hydrochloric acid. 

This compound was boiled with 12 g of dry piperidine in 120 ml of absolute benzene for 12 hours under reflux, a total of 6 g of piperidine hydrochloride being separated out. This was filtered off and the benzene solution was concentrated by evaporation. The residue was taken up in a little chloroform and the solution was applied to a dry aluminum oxide column (according to Brockmann) it was thereafter extracted with chloroform. After concentrating the solution by evaporation, an oil was obtained, which was taken up in absolute diethylether. Introduction of dry HCI gas into the cooled solution gave a precipitate which was dissolved and allowed to crystallize from isopropanol/ether. MP 193° to 199°C. 

Adsorption column chromatography has been employed to separate the constituents of pyrethrum. Florisil and aluminum oxide have been used as adsorption columns to retain much of the pigmented materials. The pyrethroids may be caused to elute with several solvents. In our experience mixtures of hexane with ethyl acetate, methanol, ethyl ether, dichloromethane, or acetone have provided different elution patterns. 

For the extraction of Tc from molybdemun irradiated by neutrons or separated from uranium fission products, inorganic sorbents, especially aliuninum oxide have widely been applied. In preparing a Tc generator from irradiated molybdenum , MoOj is dissolved in cone, nitric acid, the solution is diluted and passed through an aluminum oxide column. The column is then eluted by 0.2 N H2SO4 to extract Tc. If molybdenum is adsorbed by AljOj as molybdatophos-phate instead of molybdate, the exchange capacity of molybdenum increases from... 

Tucker et al. have separated " Tc from the fission product Mo using chromatographic aluminum oxide washed by dilute nitric acid at pH 1.5. Mo dissolved in the same dilute HNO3 of pH 1.5 is passed through the column which is then eluted with 0.1 M HNO3. Tc is only slightly adsorbed and can easily be eluted while molybdenum is retained on the column. The purity of technetium is 99.99%. 

N-Methylmorphinane. 2.7 g of the decahydro compound above in 25 ml of 85% phosphoric acid is refluxed for 70 hours and then poured onto ice. The aqueous phase is extracted with ether and the product is salted out with potassium carbonate. It is then taken up with ether, dried, and distilled at 130-132° at 0.7 mm of vacuo to give 1 g ofN-Methyl morphinane mixed with a small amount of octahydroisoquinoline, which can be removed by column chromatography. Use 0.5 g of product in 4 ml of low boiling petroleum ether and add onto the top of 30 g of aluminum oxide in a 50 ml buret or column. Elute with 20 ml portions of low boiling ether to which is added 0,0,0,1,3,5,5, and 5 ml of ethyl ether, respectively. The last three portions eluted over 0.3 g of purified product. 

Laboratory reagent grade (stabilized) tetrahydrofuran was allowed to stand over molecular sieves for 24 hours, refluxed for 2 hours with sodium wire, and finally distilled and used within 48 hours. The checkers found that it was convenient simply to percolate the tetrahydrofuran, after preliniinary drying over molecular sieves, through a column of grade I, neutral aluminum oxide, under nitrogen, directly into the reaction flask, until the required volume of solvent was collected. 

The common oxide of aluminum provides a second example, but this time, begin with the weight percent and deduce the atomic ratio. Careful laboratory analysis of aluminum oxide determines it to be approximately 53% aluminum and 47% oxygen by weight, as shown in the second column in Table 2-3. 

Monomeric isoprene is purified as described for styrene in Example 3-1 before use it is run under nitrogen through a 30-cm column packed with neutral aluminum oxide cyclohexane and 1,2-dimethoxyethane are refluxed over sodium for 6 h and distilled off under nitrogen. 

The alcohol-free chloroform required for this experiment is first prepared by running 70 ml of chloroform through a column filled with basic aluminum oxide. 

By a similar procedure, 1.0 gm of p-bromoazobenzene was isomerized in 10 ml of chloroform by irradiation with a Hanovia type 16200 ultraviolet lamp for 2 hr [108], The same authors, using the same equipment, prepared 1.0 gm of c/s-p,//-azotoluene from 6.0 gm of the trans isomer by irradiation for 4 hr. They eluted the product from an aluminum oxide column with ether [108]. 

To separate the components of this reaction mixture, the crude product is dissolved in a minimum quantity of petroleum ether. The solution is then passed through a 2 x 20 cm chromatography column packed with aluminum oxide. The nitro and azo compounds are eluted from the column first with sufficient petroleum ether. The azoxy compound is eluted with petroleum ether containing 1 % of methanol. The eluting solvent is evaporated and the residual product is recrystallized from ethanol, m.p. 117°-118°C, nematic-liquid transition point 134°C. 

The step 1 product (21 g) was dissolved in 210 ml of CH2CI2 and then treated with 77% m-chloroperbenzoic acid (41.6 g) at ambient temperature for 6 hours. The mixture was then poured into a solution of sodium hydroxide (40 g) dissolved in 150 ml of water and 200 ml of hexane and then stirred and cooled to 10°C using an ice bath. The organic layer was isolated and washed once with 100 ml of 5% Na2S204 and three times with 100 ml of 10% KC1 solution. The mixture was concentrated and the residue purified using silica gel column chromatography with hexane/ ethyl acetate, 3 1, respectively. An oil, which was obtained, was dissolved in 100 ml of 10% ethyl acetate in hexane and treated with basic aluminum oxide (3 g) to remove color on the product. After filtration 13 g of product were isolated as a liquid. 

Phthalate Esters (Method 606). These compounds are extracted with methylene chloride, concentrated, and solvent exchanged to hexane for Florisil or aluminum oxide column cleanup and EC-GC determination by using a mixed phase columnn of 1.5 SP-2250 and 1.95 SP-2401. This method is essentially the same as that for or-ganochlorine pesticides. 

Nitrosamines (Method 607). The nitrosamines are extracted with methylene chloride, treated with HC1, concentrated, and solvent exchanged to methanol for direct nitrogen-phosphorus or thermal energy analyzer (TEA) detection. Provision is made for Florisil or aluminum oxide column cleanup prior to GC analysis. The GC column liquid phase is 10 Carbowax 20 M plus 2 KOH. N-Nitrosodiphenylamine thermally degrades to diphenylamine in the GC and is measured as diphenylamine after prior removal of any diphenylamine occurring, as... 

Aluminum oxides As(V) and As(lll) adsorption on activated alumina pH dependence, kinetics, and column breakthrough. Regeneration by desorbing with NaOH. Modeling with pH-dependent Langmuir isotherm (for As) and surface complexation model (for protons) Ghosh and Yuan (1987)... 

Highly porous and granular aluminum oxide—available in three pH ranges (acidic, neutral and basic)—are used in column chromatography. Analytes are separated from the interfering compounds by virtue of their different chemical polarity. 

Normal-phase HPLC on silica columns are also used extensively in D3 analysis of vitamin products with nonpolar mobile phase containing polar modifiers. Krol et al. (66) separated D3 from pre-D3 and from a mixture of other vitamins using an adsorptive silica support introduced in 1972 (Vydac , supplied at that time by Applied Science Laboratories, Inc. State College, Penn.). The hand-packed column was used in conjunction with a mobile phase of pen-tane tetrahydrofuran (97.5 2.5). Sterule (32) used aluminum oxide as column support with chloroform as the mobile phase. Separation of D3 and its isomers and from vitamin A acetate was achieved. 

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