Acidic phase silica

I have discussed normal phase separations on silica and hydrated silica columns in which polar compounds retain and nonpolars elute. Separations have also appeared in the literature using an acid phase silica column for the separation of phospholipids. 

A review on TLC and PLC of amino adds, peptides, and proteins is presented in the works by Bhushan [24,25]. Chromatographic behavior of 24 amino acids on silica gel layers impregnated tiraryl phosphate and tri-n-butylamine in a two-component mobile phase (propanol water) of varying ratios has been studied by Sharma and coworkers [26], The effect of impregnation, mobile phase composition, and the effect of solubility on hRf of amino acids were discussed. The mechanism of migration was explained in terms of adsorption on impregnated silica gel G and the polarity of the mobile phase used. 

Szabo, G., Guczi, J., Bulman, R.A. (1995) Examination of silica-salicylic acid and silica-8-hydroxyquinoline HPLC stationary phases for estimation of the adsorption coefficient of soil for some aromatic hydrocarbons. Chemosphere 30, 1717-1727. 

One example is the separation of tricarboxylic acid cycle organic acids. These organic acids were originally separated on sulfonic acid-treated silica gel as the stationary phase material, and a chloroform and isopentyl alcohol mixture was used as the eluent. However, this eluent is not suitable for UV detection. A mixture of -hexane, THF, and ter/-butanol was therefore selected for the same separation.74... 

FIGURE 5.7 Reaction schemes for the synthesis of a poly(ethylene co-acrylic acid)-glycidoxypropyl-silica (PEAGlyP) stationary-phase. (Reproduced from Wegmann, J., et al., Anal. Chem., 73, 1814, 2001. With permission.)... 

Comparable to the other protein-coated supports are the Ultrabiosep and the BioTrap phases. The former are composed of C4, Cg, or Cis reversed-phase silica supports covered with a biological polymer which is not described in the literature (135). The latter are commercially available as Bio Trap Acid or Biotrap Amine precolumns (136). They are Cis-modified silica supports covered with -1-acid glycoprotein as a biocompatible layer. Due to the immobilized protein, this type of reversed-phase material also possesses weak ion-exchange properties. 

Bhushan and Parsad [65] resolved dansyl amino acids on erythromycin impregnated thin-layer chromatographic (TLC) silica plates. The mobile phase used was different ratios of 0.5 M aqueous NaCl-acetonitrile-methanol. Further, Bhushan and Thiong o [66] achieved the chiral resolution of dansyl amino acids on silica TLC plates impregnated with vancomycin chiral selector. The mobile phase used for this study was acetonitrile-0.5 M aqueous NaCl (10 4 and 14 3, v/v). The chiral recognition mechanisms of antibiotic CSPs in sub-SFC, SFC, CEC, and TLC modes of chromatography were found to be similar to HPLC. 

You may not be able to fix it. Zirconium columns have a different chemical structure than silica. They are more pH resistant and can be used at elevated temperatures, but they run differently than a silica Ci8. First, find out if it has a chemically bonded tetraphosphonic acid chelator. If not, you may have to add a chelator to the mobile phase. If you are not getting sharp peaks, make sure you have made new inlet tubing specifically for this column. Old tubing can ruin the performance of a new column. Run a standard mix on both columns and see how they differ. This column can give you the ability to separate mixture that you can t separate on a reverse-phase silica column. 

Acintrazole Bulk TLC phase Silica (76 24 0.5) NH4OH-MeOH Acidified acid, caffeine, and acetaminophen [1]... 

Cellulose was the first sorbent for which the resolution of racemic amino acids was demonstrated [23]. From this beginning, derivatives such as microcrystalline triacetylcellulose and /3-cyclodextrin bonded to silica were developed. The most popular sorbent for the control of optical purity is a reversed-phase silica gel impregnated with a chiral selector (a proline derivative) and copper (II) ions. Separations are possible if the analytes of interest form chelate complexes with the copper ions such as D,L-Dopa and D.L-penicillamine [24], Silica gel has also been impregnated with (-) brucine for resolving enantiomeric mixtures of amino acids [25] and a number of amino alcohol adrenergic blockers were resolved with another chiral selector [26]. A worthwhile review on enantiomer separations by TLC has been published [27],... 

Swan, T.H., Mack, Jr., E. (1925) Vapor pressures of organic crystals by an effusion method. J. Am. Chem. Soc. 47, 2112-2116. Swift, Jr., E., Hochanadel, H.P. (1945) The vapor pressure of trimethylamine from 0 to 40°C. J. Am. Chem. Soc. 67, 880-881. Szabo, G., Guczi, J., Bulman, R.A. (1995) Examination of silica-salicylic acid and silica-8-hydroxyquinoline HPLC stationary phases for estimation of the adsorption coefficient of soil for some aromatic hydrocarbons. Chemosphere 30, 1717-1727. 

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