Chromatography, column and

In the continuous process for producing phosphatidylcholine fractions with 70—96% PC at a capacity of 600 t/yr (Pig. 5) (16), lecithin is continuously extracted with ethanol at 80°C. After separation the ethanol-insoluble fraction is separated. The ethanol-soluble fraction mns into a chromatography column and is eluted with ethanol at 100°C. The phosphatidylcholine solution is concentrated and dried. The pure phosphatidylcholine is separated as dry sticky material. This material can be granulated (17). 

Application of the Design Equations to Packed Liquid Chromatography Columns and Open Tubular Gas Chromatography Columns... 

After it is washed, dried, and granulated, this silica gel has a very high specific surface area (about 700 m2-g 1) and is useful as a drying agent, a support for catalysts, a packing for chromatography columns, and a thermal insulator. 

Glass chromatography column, 15-mm i.d. x 400 mm with a stopcock Silica gel column Place a cotton wool plug at the bottom of glass chromatography column and then add anhydrous sodium sulfate in a layer 1-cm thick. Weigh 10 g of silica gel and pour it into the tube with n-hexane-benzene (1 3, v/v). Rinse the silica gel column with the same solvent system and place an anhydrous sodium sulfate in a layer 1-cm thick on the top the column. 

The simplest analytical method is direct measurement of arsenic in volatile methylated arsenicals by atomic absorption [ 11 ]. A slightly more complicated system, but one that permits differentiation of the various forms of arsenic, uses reduction of the arsenic compounds to their respective arsines by treatment with sodium borohydride. The arsines are collected in a cold trap (liquid nitrogen), then vaporised separately by slow warming, and the arsenic is measured by monitoring the intensity of an arsenic spectral line, as produced by a direct current electrical discharge [1,12,13]. Essentially the same method was proposed by Talmi and Bostick [10] except that they collected the arsines in cold toluene (-5 °C), separated them on a gas chromatography column, and used a mass spectrometer as the detector. Their method had a sensitivity of 0.25 xg/l for water samples. 

Quality assurance measures such as pre-analytical checks on instrumental stability, wavelength calibration, balance calibration, tests on resolution of chromatography columns, and problem diagnostics are not included. For present purposes they are regarded as part of the analytical protocol, and IQC tests their effectiveness together with the other aspects of the methodology. 

Amorphous silica is used as a pigment and filler in paints and coatings. It also is used as an abrasive, absorbent and catalyst support. Silica gel is a common desiccant and adsorbent. It is used in analytical chemistry as a packing material in chromatography columns and in clean-up of organic extracts to remove interference in trace analysis of organic pollutants. 

Rruss, A., Kempter, C., Gysler, 1., and lira, T., Evaluation of packed capillary liquid chromatography columns and comparison with conventional-size columns. Journal of Chromatography A 1030(1-2), 167-176, 2004. 

Majors, R. E., New chromatography columns and accessories at the 2002 Pittsburgh Conference. Part 1. LC-GC North America, 20,248-266,2002. 

Another type of mass transfer equipment, shown in Figure 6.2d, is normally referred to as the packed- (fixed-) bed. Unlike the packed column for gas-liquid mass transfer, the packed-bed column is used for mass transfer between the surface of packed solid particles (e.g., catalyst particles or immobilized enzyme particles) and a single-phase liquid or gas. This type of equipment, which is widely used as reactors, adsorption columns, chromatography columns, and so on, is discussed in greater detail in Chapters 7 and 11. 

The crude paclitaxel is dissolved in dichloromethane, filtered, and solvent-exchanged into a mixture of dimethylformamide (DMF) and formamide. This solution is loaded onto a chromatography column and eluted with acetonitrile/ water as the mobile phase. The acceptably pure fractions are combined and concentrated to remove acetonitrile, and the paclitaxel is extracted into dichloromethane. Finally, the dichloromethane is replaced with IPA (distillative exchange) and paclitaxel API is isolated by crystallization. 

B. trana-2-Isoayanoeyelohexanol. A 250-mL, one-necked, round-bottomed flask is charged with 13.72 g (70 mmol) of f (t rans-2-isocyanocycl ohexyl )oxy]-trimethylsilane, 12.12 g (210 nmol) of potassium fluoride (Note 7), and 100 mL of methanol. The reaction mixture is stirred magnetically for 5 hr at room temperature (23°C). The methanol is removed under reduced pressure on a rotary evaporator to yield a white slurry. This slurry is added to the top of a 250-g, 60-200 mesh silica gel chromatography column and the column is eluted with 20 ethyl acetate - 80 hexane solvent mixture (Note 8). The solvent is removed from those fractions containing the product under reduced pressure on a rotary evaporator to afford an oil which is redissolved in methylene chloride and the solution is filtered. The methylene chloride is removed from the filtrate under reduced pressure on a rotary evaporator to yield 8.46 g (68 mmol, 97 ) of white, crystalline trans-2-isocyanocyclohexanol, mp 57.0-59.5°C (Note 9). 

Gas-liquid chromatography separates volatile components of a mixture according to their relative tendencies to dissolve in the inert material packed in the chromatography column and to volatilize and move through the column, carried by a current of an inert gas such as helium. Some lipids are naturally volatile, but most must first be derivatized to increase their volatility (that is, lower their boiling point). For an analysis of the fatty acids in a sample of phospholipids, the lipids are first... 

Before Denby and Scott could inject the unknown solution into a chromatograph for the chemical analysis, they had to clean up the unknown even further (Figure 0-3). The slurry of chocolate residue in water contained tiny solid particles that would surely clog their expensive chromatography column and ruin it. So they transferred a portion of the slurry to a centrifuge tube and centrifuged the mixture to pack as much of the solid as possible at the bottom of the tube. The cloudy, tan supernatant liquid (liquid above the packed solid) was then filtered in a further attempt to remove tiny particles of solid from the liquid. 

Figure 22-19 (a) Atmospheric pressure chemical ionization interface between a liquid chromatography column and a mass spectrometer. A fine aerosol Is produced by the nebulizing gas flow and the heater. The electric discharge from the corona needle creates gaseous ions from the analyte. [Adapted from E. C. Huang, T. Wachs, J. J. Conboy, and J. D. Henion, Atmospheric Pressure Ionization Mass Spectrometry," Anal. Chem. 1990,62,713A ] (b) Atmospheric pressure chemical ionization probe. [Courtesy Shimadzu Scientific Instruments, Columbia, MD.J... 

Pour the gel into a glass chromatography column and equilibrate with phosphate/ saline buffer. 

Thiol Sep harose4B (200 pL) was incubated with the RNA by gently mixing at room temperature for one hour. This mixture was then transferred into a chromatography column, and the unbound RNA was eluted by gravity flow. 

The apparatus consists of a chromatography column and a flow controller (Fig. 2.141). This figure is reproduced from the original literature report, to illustrate the description of the technique below, but the equipment is commercially available (e.g. Aldrich Chemical Co., May and Baker Ltd). The flow controller is a simple variable bleed device for precise regulation of the elution rate and is constructed from a glass/Teflon needle valve. Eluate fractions are collected in... 

Hultman et al. [130] developed a LC/MS/MS method for the quantitative determination of esomeprazole and its two main metabolites 5-hydro-xyesomeprazole and omeprazole sulfone in 25 /il human, rat, or dog plasma. The analytes and their internal standards were extracted from plasma into methyl ferf-butyl ether-dichloromethane (3 2). After evaporation and reconstitution of the organic extract, the analytes were separated on a reversed-phase liquid chromatography column and measured by atmospheric-pressure positive ionization mass spectrometry. 

The most effective way to analyze quantitatively the composition of the purified methyl esters is by gas-liquid chromatography, using a flame ionization detector. As an alternative, a combination of gas-liquid chromatography and mass spectrometry can provide a wealth of information on composition and structure. The mass of material required for this type of separation depends in part on the size and type of chromatography column and the type of mass spectrometer. Amounts of material as low as 5 xg can be analyzed by this combined technique. 

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