Coatings reversed-phase

Hanson, M., Kurganov, A., Unger, K. K., and Davankov, V. A., Polymer-coated reversed-phase packings in high-performance liquid chromatography, /. Chromatogr. A, 656, 369, 1993. 

Shinbo, T., Yamaguchi, T., Nishimura, K., and Sugiura, M. (1987) Chromatographic Separation of Racemic Amino Acids by Use of Chiral Crown Ether-coated Reversed-phase Packings, J. Chromatogr. 405, 145-53. 

T. Shimbo, T. Yamaguchi, K. Nishimura, and M. Sugiura, Chromatographic separation of racemic amino acids by use of chiral crown ether-coated reversed-phase packings,/. Chromatogr 405 (1987), 145. 

Michael Hanson and Klaus K. Unger, CoUn T. Mant, and Robert S. Hodges Polymer-coated reversed-phase packings with controlled hydrophobic properties. I. Effect on the selectivity of protein separations, J. Chromatogr. A, 599(1-2), (1992) 65-75... 

Davankov ligand A form of octadecyl Coated Reverse phase Underivatized... 

Chemical stabiUty studies are monitored by siUca gel thin-layer chromatography (dc) or by high performance Hquid chromatography (hplc) using a reverse-phase C g coated column (24). Hplc peaks or dc spots are visualized by thek uv absorption at 245 nm the tic spots can also be detected by ceric sulfate or phosphomolybdic acid staining. 

Naphthalenedisulfonate-acetonitrile as the only mobile phase with a silica column coated with a crosslinked aminofluorocarbon polymer has proven to be an effective combination for the separation of aliphatic anionic surfactants. Indirect conductivity and photometric detection modes are used to monitor these analytes. The retention of these surfactants is found to depend on both the ionic strength and the organic solvent content of the mobile phase. The mechanism of retention is considered to be a combination of both reverse phase and ion exchange processes. Selective separation of both alkanesulfonates and... 

It must be kept in mind, however, that the PIC reagents themselves will not be able to enter the pores of the reverse phase due to ion exclusion and will merely coat the external surface of the stationary phase. Nevertheless, under these circumstances ions will interact with the surface charges and materials will be retained and separated due to ionic interactions. However, at higher solvent concentrations, it has also been suggested that the PIC reagents work in an entirely different manner. 

Tswett s initial column liquid chromatography method was developed, tested, and applied in two parallel modes, liquid-solid adsorption and liquid-liquid partition. Adsorption ehromatography, based on a purely physical principle of adsorption, eonsiderably outperformed its partition counterpart with mechanically coated stationary phases to become the most important liquid chromatographic method. This remains true today in thin-layer chromatography (TLC), for which silica gel is by far the major stationary phase. In column chromatography, however, reversed-phase liquid ehromatography using chemically bonded stationary phases is the most popular method. 

Figure 8.43 Separation of enantiomers using complexation chromatography. A, Separation of alkyloxiranes on a 42 m x 0.2S mm I.O. open tubular column coated with 0.06 M Mn(II) bis-3-(pentafluoro-propionyl)-IR-camphorate in OV-ioi at 40 C. B, Separation of D,L-amino acids by reversed-phase liquid chromatography using a mobile phase containing 0.005 M L-histidine methyl ester and 0.0025 M copper sulfate in an ammonium acetate buffer at pH 5.5. A stepwise gradient using increasing amounts of acetonitrile was used for this separation.

Superheated water at 100°-240 °C, with its obvious benefits of low cost and low toxicity, was proposed as a solvent for reversed-phase chromatography.59 Hydrophobic compounds such as parabens, sulfonamides, and barbiturates were separated rapidly on poly(styrene-divinyl benzene) and graphitic phases. Elution of simple aromatic compounds with acetonitrile-water heated at 30°-130 °C was studied on coupled colums of zirconia coated with polybutadiene and carbon.60 The retention order on the polybutadiene phase is essentially uncorrelated to that on the carbon phase, so adjusting the temperature of one of the columns allows the resolution of critical pairs of... 

Li, J. and Carr, P.W., A study of the efficiency of polybutadiene-coated zirconia as a reversed-phase chromatographic support, Anal. Chem., 69(11), 2193,1997. 

A PRP -1 (Hamilton Reno, NV) reversed phase column was coated with cetylpyridinium and eluted with tetramethylammonium salicylate acetoni-trile water.89 The separation was comparable to that observed on conventional ion exchange. Coated phases were also used to separate oxalate complexes of manganese, cobalt, copper, and zinc.90 Reversed phase silica supports were coated with poly(N-ethyl-4-vinylpyridinium bromide), poly(dimethydiallylammonium chloride), poly(hexamethyleneguanidinium... 

Other applications that utilize different types of reversed-phase columns in both dimensions have been advocated by Carr (Stoll et al., 2006) for metabolomics work in small-molecule separations. These stationary phases include a pentafluorophenyl-propyl stationary phase in the first dimension and a carbon-coated zirconia material stationary phase in the second dimension. A common mistake in 2D method development is to mismatch the solvent system the two solvent systems must be miscible as discussed below. 

Ito et al. [175] used this technique employing octadecyl silane reverse phase columns coated with cetyltrimethyl ammonium chloride for the determination of nitrite and nitrate in seawater. 

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