Cleanup alumina

MSPD extn/ cleanup, alumina column cleanup... 

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

Air Collect on hexylene glycol-alumina adsorbent sampler extract cleanup with Florisil GC/FPD 0.1 ng/m 53.4 Stanley et al. 1971... 

To obtain reliable chromatograms in the final step of the determination of the analytes by LC or GC, it is important to remove interfering signals resulting from coelution of other compounds. To this end, a variety of techniques are applied for cleanup of the sample extract. The most effective procedures for sample cleanup for PAH measurements are partitioning between M, N-dimethylformamide/water/cyclo-hexane and LC on silica and on Sephadex LH 20. Other cleanup procedures include LC on alumina or XAD-2 and preparative thin-layer chromatography. 

For multi-analyte and/or multi-matrix methods, it is not possible to validate a method for all combinations of analyte, concentration and type of sample matrix that may be encountered in subsequent use of the method. On the other hand, the standards EN1528 andEN 12393 consist of a range of old multi-residue methods. The working principles of these methods are accepted not only in Europe, but all over the world. Most often these methods are based on extractions with acetone, acetonitrile, ethyl acetate or n-hexane. Subsequent cleanup steps are based on solvent partition steps and size exclusion or adsorption chromatography on Florisil, silica gel or alumina. Each solvent and each cleanup step has been successfully applied to hundreds of pesticides and tested in countless method validation studies. The selectivity and sensitivity of GC combined with electron capture, nitrogen-phosphorus, flame photometric or mass spectrometric detectors for a large number of pesticides are acceptable. 

For soil samples, sufficient sample cleanup could be conducted even if the alumina column was changed to a Sep-Pak Alumina N cartridge (Waters) by the following process. The entire sample of the dried n-hexane extract (Section 6.2) is introduced into a Sep-Pak Alumina N cartridge, and the column is washed with 50 mL of n-hexane. Subsequently, pyriminobac-methyl is eluted with 3 mL of ethyl acetate, the solvent is evaporate to dryness under reduced pressure and the residue is dissolved in an appropriate volume of acetone for GC analysis. 

Second cleanup Transfer the n-hexane solution into an alumina cartridge preconditioned with 5 mL of n-hexane. Rinse the cartridge with 10 mL of acetone-n-hexane (1 9, v/v) and elute thenylchlor with 7 mL of acetone-n-hexane (3 17, v/v). Concentrate the eluate to dryness by rotary evaporation at 40 °C and dissolve the residue in 5 mL of acetone for GC analysis. 

The use of SPE with porous materials such as alumina, diatomaceous earth, Horisil and silica for the cleanup of fat-soluble organochlorine pesticides in fatty foods such as meat, flsh, shellfish, milk and vegetable oils has been well documented. The choice of elution solvents is critical because relatively small amounts of lipid in the final extract can cause rapid deterioration of GC capillary columns and also contaminate the gas chromatograph. A number of workers have used a porous material in tandem with Cig to effect an improved cleanup.Di Mucchio employed a multicartridge system comprising Extrelut, silica and Cig to extract organophosphorus pesticides from oils and fatty extracts. Relatively few literature applications include the pyrethroids, but Ramesh and Balasubramanian reported a simple carbon-based SPE method for the analysis of pyrethroids in vegetable oil. 

Prior to the development of modern SPE formats, liquid-solid partitioning with charcoal, silica, Florisil, and/or alumina was common to aid in the removal of lipids in the determination of nonpolar pesticides, but these sorbents are less useful in the cleanup of semi-polar and polar pesticides owing to the large elution volumes needed. Applications of modern SPE are discussed in Section 3.2. 

The development of solid-phase extraction (SPE) absorbents such as silica gel, alumina and Florisil tremendously aided in the purification or cleanup of pesticide residues from water. 

The sample is homogenized with acetonitrile. An aliquot of the extract is evaporated to dryness and the residual material is dissolved in ethyl acetate-toluene (3 1, v/v), and subjected to cleanup by gel permeation chromatography (GPC). After GPC, the sample is subjected to an alumina and Florisil SPE cleanup procedure. The concentrated eluate is analysed by gas chromatography/thermionic nitrogen-specific detection (GC/TSD). 

Packing materials for column chromatography. Adequate cleanup can be achieved with alumina instead of silica gel. Activated carbon is not suitable for sample cleanup of ripe orange and leaf. 

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. 

Each batch of alumina, Horisil, and silica gel used in a cleanup column must be checked for recovery of pyriproxyfen. If the recovery of pyriproxyfen is <90%, the elution volume and/or solvent mixture must be adjusted until suitable recoveries are obtained. 

DBDPE 100°C, 1,500 psi cleanup H2S04, acidic silica gel and basic alumina... 

TBBPA Soxhlet toluene cleanup 1. Multi layer Si02-AgN03, 2. GPC Bio-Beads S-X3, 3. HPLC on a nitro column, 4. micro alumina... 

Alumina Different pH and activity ranges available for different cleanup needs May decompose or irreversibly adsorb some compounds... 

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... 

Various additional (secondary solvent cleaning) procedures have been proposed, including vacuum distillation [30], treatment with macroreticular anion-exchange resins [31], and treatment with activated alumina [32,33]. These secondary cleanup operations increase solvent quality, and continue to be studied to better evaluate their process and economic advantages. In the French UP3 Purex plant, vacuum distillation is used to regulate TBP concentration and solvent quality with beneficial effects. The latter include... 

P14 The most common cleanup methods are as follows shaking the extract with concentrated sulfuric acid, Florisil, alumina,and silica gel and using size exclusion chromatography (SEC). (From Llompart et ah, 2001)... 

Solid-phase extraction seems to be more suitable for multiresidue cleanup. This procedure has become the method of choice for isolation and/or cleanup of -lactam antibiotics from biological matrices, because it requires low solvent consumption, it is generally less time-consuming and labor-intensive, and offers a variety of alternative approaches that allow better extraction of the more hydrophilic -lactam antibiotics such as ampicillin. It is usually performed using reversed-phase Ci8 (69-71, 80-83, 90, 92-94, 99, 107, 112-116, 121-125) or Cg (103), anion-exchange (95, 124), and polar diol (95) or alumina (101, 113) sorbents. In recent applications, some workers demonstrated the potential of online solid-phase extraction in the determination of monobasic penicillins in bovine muscle tissues using a reversed-phase Cis 5 m cartridge and an automated... 

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... 

Cleanup of nitro furans from coextracted substances and concentration of the extracts can also be accomplished with solid-phase extraction columns. Nonpolar sorbents such as reversed-phase (Cis) (37, 159-161, 170, 173, 177) or XAD-2 (178) materials are usually employed, since they provide high recovery of the analytes. However, in many cases, cleanup on these nonpolar sorbents is not effective in removing interfering substances from the extracts. Therefore, polar sorbents such as silica (29, 162), alumina (160, 179, 180), or aminopropyl (175, 176) materials are also frequendy employed as a more powerful alternative for extract cleanup. 

Cleanup and concentration of quinolones from coextracted matrix constituents can also be accomplished with solid-phase extraction columns that contain either nonpolar reversed-phase (Cis) sorbents (177, 197, 198), or polar sorbents such as alumina (189-191, 194), aminopropyl (182, 187), and propylsulfonic acid (188). Reversed-phase Cis material has also been employed as the sorbent in matrix solid-phase dispersion cleanup for the determination of oxolinic acid in catfish muscle (206). 

Honey alumina and AG MP-1 column cleanup, derivatization with N-(1 - naphthyl)- ethylenediamine Acetate buffer, pH 1 - - Fourth- 76-98% 3 ppm/ 212... 

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