Fractions from adsorption chromatography

Figure 2. Fluorescence spectrum in a nitrogen matrix at 15 K (excited by a 2.5-kW mercury-xenon lamp) of an adsorption chromatography fraction from a coking plant water sample. Compounds BbF, benzo[b]fluorene C, chrysene BeP, ben-zo[e]pyrene P, pyrene BkF, benzo[k]fluoranthene BaP, benzo[a]pyrene U, unknown ( ).

Figure 3. Fluorescence spectra excited by a dye laser at 389.2 nm in an r -heptane matrix at 15 K of an adsorption chromatography fraction from a coking plant water sample (left,) and of pure benzo[a]pyrene (right,). Note that the two spectra are virtually superimposable ( 1).

Biggs and co-workers used a DC arc plasma detector to measure iron, nickel, vanadium, and sulfur profiles from SEC of petroleum and its distillation and adsorption chromatography fractions [118-123]. They found that the metal species were present as three distinct molecular sizes. They identified the low molecular weight ones as metalloporphyrins. They also measured the variety of siliconpolysiloxane polymers and synthetic alkyl- and arylsulfonates [124]. 

The enantioselective determination of 2,2, 3,3, 4,6 -hexachlorobiphenyl in milk was performed by Glausch et al. (21). These authors used an achiral column for an initial separation, followed by separation of the eluent fraction on a chiral column. Fat was separated from the milk by centrifugation, mixed with sodium sulfate, washed with petroleum ether and filtered. The solvent was evaporated and the sample was purified by gel permeation chromatography (GPC) and silica gel adsorption chromatography. Achiral GC was performed on DB-5 and OV-1701 columns, while the chiral GC was performed on immobilized Chirasil-Dex. 

A method has been described [55] for separating polychlorinated biphenyls from chlorinated insecticides. This procedure involves adsorption chromatography on alumina and charcoal columns, elution with increasing fractional amounts of hexane on alumina columns, and with acetone-diethyl ether on charcoal columns. The polychlorinated biphenyls and chlorinated pesticides are then determined by gas chromatography-mass spectrometry on the separate eluates without interference. 

Purification of the Organoselenium Compounds. After the oxidation of 2-butene with selenium dioxide was completed, the acetic acid solvent and the volatile reaction products were distilled at reduced pressure (10 mm. HgA). The residue, a yellow oil, was purified by adsorption chromatography in a column packed with silica gel. n-Hexane and ethyl ether were used as eluents. The same procedure was applied to the fractionation and purification of the organoselenium compounds obtained from the oxidation of bis(l-methyl-2-acetoxypropyl) selenide with peracetic acid. 

DOM is derived from autochthonous sources such as phytoplankton and photosynthetic bacteria (16) at Big Soda Lake near Fallon, Nevada. This lake is alkaline (pH 9.7) and chemically stratified. It contains DOC concentrations as high as 60 mg/L and dissolved salt concentrations as high as 88,000 mg/ L (17). The DOM in this lake is colorless. The fulvic acid fraction was isolated by adsorption chromatography (Amberlite XAD-8 resin) (18) and by zeo-trophic distillation of water from N,N-dimethylformamide (19). Average molecular model synthesis was achieved in a manner similar to that used for fulvic acid from the Suwannee River. The characterization data are presented in Table I and the structural model is presented in Structure 2. 

Fig. 30. Chromatographic cross-fractionation of300 mg poly(styrene-6-methyl methacrylate) with 47 wt % styrene. SEC curves of the fractions obtained by column adsorption chromatography. The large SEC curve is from the non-fractionated sample. (From Ref.1321 with permission)...

The removal of sterols, vitamin E vitamers, carotenoids, and other interfering material from the unsaponifiable fraction of food samples has been achieved using one or more of the following techniques coprecipitation of sterols with digitonin (91), precipitation of sterols from a methano-lic solution (195,209), adsorption chromatography on open columns of alumina (70,91,96), thin-layer chromatography on silica plates (209), and solid-phase extraction on silica (68,100) and reversed-phase (210) cartridges. 

Sulfur compounds in the gas oil fractions from two bitumens (Athabasca oil sand and Cold Lake deposit)> a heavy oil (Lloydminster) from Cretaceous reservoirs along the western Canada sedimentary basin, and a Cretaceous oil from a deep reservoir that may be mature (Medicine River) are investigated. The gas oil distillates were separated to concentrates of different hydrocarbon types on a liquid adsorption chromatographic column. The aromatic hydrocarbon types with their associated sulfur compounds were resolved by gas chromatographic simulated distillation and then by gas solid chromatography. Some sulfur compounds were further characterized by mass spectrometry. The predominant sulfur compounds in these fractions are alkyl-substituted benzo- and dibenzothiophenes with short side chains which have few dominant isomers. 

Isoenzymes. Multiple forms of citrus PE were reported by Evans and McHale (AO) and Versteeg et al. (Al). PE was purified from West Indian limes and Navel oranges by fractionation of the whole fruit extracts with (NH. SO (AO-65%), adsorption and elution from Sephadex G-75 columns (AO). The PE active fractions were combined and concentrated before separation into two active PEs on the basis of their elution volume from a DEAE Sephadex A-50 column. Orange PEI (OPEI) and lime PEI (LPEI) had the same elution volume also OPEII and LPEII had the same elution volume. A higher concentration of NaCl was required at all pH values for optimum activity of OPEI and LPEI than of OPEII and LPEII. When the component parts of oranges were separately analyzed chromatographi-cally with DEAE-Sephadex A-50, OPEI was detected only in the peel, whereas OPEII was identified in juice sacs and section walls (AO). 

Separation, Characterization and Analysis of the Distillate Fractions. Results from the analyses of the <200° C coal-liquid distillates (after removal of trace quantities of acids and bases) are summarized in Table IV. Results from the dual silica-gel/alu-mina-gel adsorption chromatography separations of the 200° to 325° C, 325° to 425° C, and 425° to 540° C coal-liquid distillates are summarized in Table V. Data for the acid and base extracts of the polyaromatic-polar adsorption fractions are also included in Table V. Summary data on analysis of the saturate fractions are listed in Table VI. Data in Table VI show a trend toward higher percentages of zero- and one-ring saturates in lower-rank coals. 

Table V. Fraction Yields from Adsorption Chromatography and Acid-Base Separations, Weight Percent...

Function of Pre-HPLC Column. The schematic in Figure 6 for a HPLC chromatogram representative of extracts of agricultural products illustrates use of silica gel adsorption chromatography for the pre-HPLC cleanup step. The schematic shows that (A) a large part of the co-extractives can be removed in the first fraction from the precolumn, (B) the polarity of the mobile phase can be adjusted so the pesticide elutes in pre-HPLC column fraction B where the eluate can be collected and concentrated for injection into the HPLC, while (C) more polar compounds that would otherwise appear during HPLC have been eliminated by permanent adsorption on the pre-HPLC Column. 

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