Silica gel bonding

Enomoto, N., Furukawa, S., Ogasawara, Y., Akano, H., Kawamura, Y., Yashima, E., and Okamoto, Y. (1996) Preparation of silica gel-bonded amylose through enzyme-catalyzed polymerization and chiral recognition ability of its phenylcarbamate derivative in HPLC, Anal. Chem. 68, 2798-2804. 

Facklam, C., Pracejus, H., Oehme, G., and Much, H., Resolution of enantiomers of amino acid derivatives by high-performance liquid chromatography in a silica gel bonded chiral amide phase, J. Chromatogr., 257, 118, 1983. 

As regards the lipids, two types of adsorbents are available, one of which is a form of silica gel and is utilized in normal-phase HPLC, and the other of which can be a silica gel bonded to a hydrophobic chain and is employed in reverse-phase HPLC. In normal-phase HPLC the phospholipids appear to be separated based on the molecular classes present (PE, PC, Sph, etc.), whereas in reverse-phase HPLC the separation is closely related to the lipophilic character of the acyl (fatty acyl, hydrocarbon chain) of the particular phospholipids. High-quality adsorbents suitable for HPLC are easily available from commercial companies. 

Chromatographic System (See Chromatography, Appendix IIA.) Use a liquid chromatograph equipped with a refractive index detector that can be maintained at a constant temperature of 25°, a 25-cm x 4.6-mm (id) column packed with 10- im porous silica gel bonded with aminopropylsilane (Alltech 35643, or equivalent), and a guard column that contains the same packing. Maintain the column at a constant temperature of 25° 2°, and the flow rate at about 2.0 mL/min. Inject 20 pL of System Suitability Preparation into the chromatograph, and record the peak responses as directed under Procedure. The relative standard deviation for replicate injections is not more than 2.0%, and the alpha-Cyclodextrin and beta-Cyclodextrin peaks exhibit baseline separation, the relative retention times being about 0.8 and 1.0, respectively. 

Syloid . [Wit. Grace/Davison] Silica gels bonding agent for adhesives. 

The type, if any, of open-column, flash, or vacuum-column chromatography used. These were divided into silica gel bonded phases (e.g, ODS, C-8, Diol, CN) or gel permeation on nonfunctionalized resins, including both size and partition chromatography systems (e.g., Sephadex LH-20, Sephadex LH-60, NS Gels, BioBeads SX-2, SX-4, SX-8, AMBERLITE XAD-2, XAD-4, and XAD-7, TSK-G3000S gel). 

The passage of chloride ion through a column of an anion-exchange resin leads to an enrichment of C1 in the first fractions and a depletion in the last fractions (Figure 1). This behaviour can be accounted for if the lighter isotope has the larger ionic radius. The separation of, and detection-limits for, the halide ions on a thin layer of activated silica gel (bonded on aluminium foil) have been studied... 

Some other methods are immobilized by amino bonds. For example, 6-chlorpromazine-CD and single-6-sulfonic add ester-CD are used as intermediates. Silica gel carrier with the amino groups is used to immobilize CDs to obtain CD silica gel bonded phase. 

In general, as newer detection techniques and sensitivities are developed in the analytical laboratory, the demands are more stringent regarding the purity of the new products whether they are solvents or thin-layer plates. This is particularly true for the silica gels, bonded phases, or binders used in HPTLC plates to be used in TLC-MS work. If doing elution-based TLC-MS or desorption-based TLC-MS, the requirements are the same. 

These functions have been used to evaluate 171 possible two-dimensional solvent systems for separating a mixture of 15 steroids [43]. These systems included 13 candidate solvent systems and four stationary phases (silica gel, bonded C2, bonded C g, and bonded diphenyl). A total of 1681 simulated chromatograms were computer evaluated for each of the possible 171 systems in order to obtain an optimum for the entire two-dimensional solvent domain. These optimum values were then used to rank the different systems. In addition, the best of the 1681 simulated chromatograms for each two-dimensional system was printed in order to allow ranking based on visual evaluation. 

Reactions.—New chiral stationary phases, such as the silica gel-bonded fluoro-alcohol (47), have been developed for the h.p.l.c. separation of enantiomers chiral alcohols are separated as their 3,5-dinitrobenzoate esters. 

In LPLC, a mobile phase is allowed to flow through a densely packed sorbent. The separation mechanism is adsorption or size-exclusion depending on the choice of packing material for the stationary phase (adsorption silica gel, bonded-phase silica gel, alumina, polystyrene size-exclusion polyacrylamide, carbohydrates). This is almost similar to... 

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