Column chromatography types

Method A A solution of the azidoquinoline (5 mmol) in 3M KOMe in MeOH (40 mL) and dioxane (40 mL) was irradiated under N2 using a water-cooled, 125-W medium-pressure Hg lamp until all the azide [as measured by the disappearance of u(N3) at 2120 cm" 1 or by TLC] had reacted (4-10h). The photolysate was left to stand at 20 C for 24h then neutralized cautiously by the addition of 4M IICI in MeOH. The solvent was removed under reduced pressure and the crude product was purified initially by column chromatography on alumina (Type H, toluene), then finally by crystallization (petroleum ether). 

A mixture of 4,5-di(pentyloxy)phthalonitrile (A 69 mg, 0.23 mmol), 3,4,5,6-tetraphenylphthalonitrile (B lOOmg, 0.23 mmol), Ni(0Ac)2 (35 mg, 0.2mmol). and catalytic amounts of DBU in pentan-l-ol (3mL) was heated under N2 for 24 h under reflux. The cooled blue-green solution was poured into MeOH/H20 (5 1, 50 mL), and the precipitate formed was centrifuged, washed with MeOH, and dried in vacuo. The separation of the prepared compounds was performed by column chromatography (toluene/hexane 1 1). The fractions were collected and the solvent evaporated. The order of elution was ABBB (0.5 mg, 0.1 %), ABAB (7.5 mg, 1.4%), AABB (2 mg, 0.5%), AAAB (15 mg, 2.3%) and AAAA (9 mg, 1.6%). No BBBB-type phthalocyanine was formed. 

Purification of aequorin. The purification method of aequorin reported by Shimomura et al. (1962) was essentially the repetition of column chromatography on DEAE-cellulose, the only usable, efficient chromatographic adsorbent available at the time. Since then, various different types of chromatographic media have been developed, and the purification method has been steadily improved. 

In order to reduce the time-consuming open-column chromatographic processes, conventional methods of hydrocarbon-group-type separation have been replaced by MPLC and HPLC. Flash column chromatography is a technique less commonly applied than open-column version, but several applications have been described [2,24—27]. The common technique version is to use a silica-gel-filled column for example, 230 to 400 mesh 20 X 1 cm column size with a back pressure of 1.5 X 10 Pa of an ambient gas such as nitrogen. Solvents are similar to the ones apphed in the case of open-column chromatography fractionations. 

Principles and Characteristics Column liquid chromatography is the parent of all other types of chromatography. The technique used by Tswett is now called classical open-column liquid chromatography or simply LC. In column chromatography the stationary phase is contained in a column and the mobile phase flows... 

Dry column chromatography [528] provides several improvements over traditional column chromatography, such as better resolution and high speed. Another important characteristic is the near-quantitative applicability of TLC results in dry column analysis. Knowledge of the TLC characteristics of a sample is useful before column chromatography is employed. Careful control of the moisture content of the adsorbent is crucial to the dry column as well as other types of chromatography. 

Construction of the cyclopentane ring was accomplished by utilization of Trosf s Pd-mediated diastereoselective [3+2] trimethylenemethane (TMM) cycloaddition [4] on the cinnamate 5 having an Evans type chiral auxiliary [4b], The resulting diastereomeric mixture (3 1 at best) of 7a and 7b was separated by careful silica gel column chromatography (7a is less polar than 7b under normal phase). Puri-... 

There are many combinations of separations techniques and methods of coupling these techniques currently employed in MDLC systems. Giddings (1984) has discussed a number of the possible combinations of techniques that can be coupled to form two-dimensional systems in matrix form. This matrix includes column chromatography, field-flow fractionation (FFF), various types of electrophoresis experiments, and more. However, many of these matrix elements would be difficult if not impossible to reduce to practice. 

Air bubbles are the nasties in HPLC work. They cause the same type of troubles as with wet-column chromatography, and you just don t want them. So there s usually a bubble trap (Fig. 112) before the eluent reaches the pump. This device is quite simple, really. Bubbles in the eluent stream rise... 

Heise and Litz [26] investigated the extraction behaviour of surfactants (LAS, NPEO and cationics) from sand comparing Soxhlet extraction, accelerated solvent extraction (ASE) and microwave-assisted extraction. Fractionation of the three surfactant types anionic, non-ionic and cationic, was accomplished by column chromatography with aluminium oxide. Soxhlet extraction and ASE of spiked sand with methanol—stored during 7 days prior to extraction—gave similar recoveries for both LAS and NPEO with values between 88 and 116%. Less efficient extraction was achieved by microwave extraction (79% for NPEO). 

Stoddart and co-workers have made use of Frechet-type dendrons as dendritic stoppers for self-assembled [n]rotaxanes [65]. The solubility enhancement that results from incorporating dendritic wedges at the termini facilitated the purification of these materials by column chromatography despite the polycationic nature of their bipyridinium backbone. Again, the dendritic wedges did not alter the electrochemical characteristics of the viologen subunits. Flowever, the enhanced solubility resulting from the presence of the dendritic components en-... 

Buchacher et al. [43] discussed the continuous separation of protein polymers from monomers by continuous annular size exclusion chromatography. The P-CAC used for the experiments was a laboratory P-CAC type 3 as described in Table 1. The results were compared to conventional batch column chromatography in regard to resolution, recovery, fouling, and productivity. The protein used in the studies was an IgG preparation rich in aggregates. Under the conditions used, the polymers could be separated from the monomers, although no baseline separation could be achieved in either the continuous or the batch mode. The... 

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