Alumina column cleanup

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. 

Alumina column cleanup and separation of petroleum wastes... 

There are two noncolumn cleanup methods, one of which uses acid partition (EPA SW-846 3650) to separate the base/neutral and acid components by adjusting pH. This method is often used before alumina column cleanup to remove acid components. The other method (EPA SW-846 3660) is used for sulfur removal and uses copper, mercury, and tetrabutylammonium sulfite as desulfurization compounds. Sulfur is a common interfering compound for petroleum hydrocarbon analysis, particularly for sediments. Sulfur-containing compounds are very common in crude oil and heavy fuel oil. Elemental sulfur is often present in anaerobically biodegraded fuels. Thus, abnormally high levels of sulfur may be... 

H2SO4/sodium tungstate extn, alumina column cleanup, SPE cleanup, on-line trace enrichment on LiChrosorb RP-18, 5 m, preconcn column and switching to analytical column... 

MSPD extn/ cleanup, alumina column cleanup... 

Chicken CHClVEtOAc extn, liver alumina column cleanup, liq-liq partn, ion-pair extn... 

EtOAc extn, liq-liq partns, Sephadex LH-20 column cleanup, alumina column cleanup... 

Neutral form is less active than the basic grade and is used to separate aldehydes, ketones, esters, and lactones, etc. Acidic form (pH 4 to 5) is used to separate strong acids and acidic pigments. Alumina column cleanup is also used to separate petroleum wastes. 

In alumina column cleanup, the column is first preeluted with ether-pentane mixture (30 70) before the sample extract is transferred onto the column. It is then successively eluted with ether-pentane mixture of 30 70 and 50 50% composition, respectively. This separates A-nitrosodiphenylamine. The latter elutes into the first fraction, from the interfering substance diphenylamine which goes into the second fraction along with the analytes A-nitrosodimethylaminc and A-nitrosodi-n-propy lamine. A small amount of the latter compound is also eluted into the first fraction. A cleanup procedure for other nitrosamines (not classified under U.S. EPA s priority pollutants) should generally be the same as described above. The composition of ether-pentane mixture and the elution pattern, however, must be established first before performing the cleanup. 

A study compared ASE and SFE to Soxhlet and sonication in the determination of long-chain trialkylamines (TAMs) in marine sediments and primary sewage sludge [89], The recoveries of these compounds by SFE at 50°C and 30 MPa with CO2 (modified dynamically with methanol or statically with triethylamine) were 10 to 77% higher than those by Soxhlet or soni-cation with dichloromethane methanol (2 1). ASE at 150°C and 17 MPa with the same solvent mixture as Soxhlet showed the highest extraction efficiency among the extraction methods evaluated. SFE exhibited the best precision because no cleanup was needed, whereas Soxhlet, sonication, and ASE extracts required an alumina column cleanup prior to analysis. SFE and ASE used less solvent and reduced the extraction time by a factor of 3 and a factor of 20 compared to sonication and Soxhlet, respectively. 

Another major problem in this work concerned the gas chromatographic overlap of several compounds. The use of alternate columns was insufficient for complete resolution of all the phenols. An alumina column cleanup and separation technique was devised which overcame most of the problem. 

In addition to eliminating interferences, the column also separates those insecticide pairs that are poorly resolved by gas chromatography— e.g., dieldrin and DDE. Figure 1 shows the improvement resulting from alumina column cleanup and separation on the gas chromatogram of the dieldrin fraction. The activity of alumina as purchased was found to vary slightly with age and lot therefore, l.Q-1.5% water had to be... 

Figure 1. Effect of alumina column cleanup in gas chromatography...

A. Muscle tissue of poisoned fish after acetonitrile cleanup B. Muscle tissue of poisoned fish after alumina column cleanup... 

Ambient Air Sample collection on glass fiber filter and PUF cartridge Soxhiet extraction alumina column cleanup GC/ECD >1 ng/m 36-94 EPA 1988b (method TO-4)... 

U.S. Environmental Protection Agency Test Method 361 IB, Alumina Column Cleanup and Separation of Petroleum Wastes, U.S. Government Printing Office, Washington, pp. 1-7, 1996. 

Alumina column cleanup makes use of highly porous granular aluminum oxide. Available in acidic, neutral, and basic pH ranges, this solid is packed into a column topped with a water-absorbing substance over which the sample is eluted with a suitable solvent, which leaves interferences on the column. After elution, the sample is concentrated, exchanged with another solvent if necessary, then analyzed. Florisil... 

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