Liquid chromatography polysiloxane

Our initial attempts to separate the Cj and Dj isomers of 5 (G = 1) used octadecyl polysiloxane (ODS) as high performance liquid chromatography (HPLC) stationary phase and mixtures of acetonitrile/HjO or methanol/HjO as mobile phases. Under these classical reverse-phase conditions, the resulting efficiencies were extremely poor because of the low solubility of 5 (G = 1) in both mobile phases. By contrast, mixed mobile phases which contained acetonitrile (ACN) with some percentages of a cosolvent such as tetrahydrofuran (THF) substantially improved... 

Since Pasteur separated crystalline sodium ammonium tartrate manually in 1848, many researchers have worked on the subject of enantiomeric separation. In 1939 Henderson and Rule fully separated derivatives of camphor by column chromatography using lactose as a stationary phase material [1]. Gil-Av et al. [2] were able to separate amino acid derivatives on a polysiloxane-based stationary phase by gas chromatography (GC) in 1966. Since then many approaches for a successful distinction between enantiomers have been developed for capillary GC and liquid chromatography [3]. It is still a current topic for researchers searching for chiral separation with SciFinder [4] results in 812 hits and searching for chiral recognition leads to 285 hits for the year 2003 only. 

Jones, B.A., Bradshaw, J.S., Nishioka, M., and Lee, M.L., Synthesis of smectic liquid-crystalline polysiloxanes from biphenylcarboxylate esters and their use as stationary phases for high-resolution gas chromatography, J. Org. Chem., 49, 4947, 1984. 

K. Markides, M. Nishioka, et al., Smectic biphenylcarboxylates ester liquid crystalline polysiloxane stationary phase for capillary gas chromatography, Anal. Chem., 57 1296-1299(1985). 

Many of the column coatings used in liquid chromatography have been applied to supercritical-fluid chromatography as well. Typically, these are polysiloxanes (see Section 31B-3) that are chemically bonded to the surface of silica particles or to the inner silica wall of capillary tubing. Film thicknesses are 0.05 to 0.4 p,m. 

Terfloth, G.J. Pirkle, W.H. L5mam, K.G. Nicolas, E.C. Broadly applicable polysiloxane-based chiral stationary phase for high-performance liquid chromatography and supercritical fluid chromatography. J.Chromatogr.A, 1995, 705, 185-194... 

Popp, P., Bauer, C., Paschke, A., and Montero, L., Application of a polysiloxane-based extraction method combined with column liquid chromatography to determine polycyclic aromatic hydrocarbons in environmental samples. Anal. Chim. Acta, 504, 307-312, 2004. 

Chang-Chien, G., Terminally carboxyl oligo(ethylene oxide) monomethyl ether-substituted side chain liquid crystalline polysiloxane polymer as stationary phase in capillary gas chromatography for the separation of polynuclear aromatic hydrocarbons, J. Chromatogr. A, 808, 201-209, 1998. 

The Amino Acid-Peptide Polysiloxane Stationary Phases Peptide-Dimethylpolysiloxane Chiral Stationary Phases Peptide-Phenylpolysiloxane Chiral Stationary Phases Cyanopolysiloxane Peptide Chiral Stationary Phases The Polysiloxane-Cyclodextrin Based Stationary Phases Chiral Liquid Chromatography... 

Wolff, R.L. Analysis of Alpha-Linolenic Acid Geometrical Isomers in Deodorized Oils by Capillary Gas-Liquid Chromatography on Cyanoalkyl Polysiloxane Phases A Note of... 

Jing, P. Fu, RJ4. Dai, RJ. Gu, J.L. Huan, Z. Chen, Y. Consequence of diluting modified p-cyclodextrins in a side-chain crown ether polysiloxane and in a side-chain liquid-crystaUine polysiloxane-containing crown ether as stationary phases in capillary gas chromatography. Chromatographia 1996, 43, 546 550. 

Analysis of reaction products - Liquid reaction products were analyzed by gas chromatography using a capillary column (type WCOT Fused Silica, stationary phase 5% phenyl-methyl-polysiloxane length - 50 m ID - 0.32 mm, OD - 0.45 mm film thickness - 0.25 pm). 

A much better agreement between theory and experiment is found in the closely-related field of macrocyclisation equilibria. Investigations of the cyclic populations in ring-chain equilibrates set up in typical polymeric systems such as polyesters, polyethers, polysiloxanes, and polyamides take a major advantage from the relative ease with which the cyclic fraction can be separated from the linear fraction and analysed for the relative abundance of the individual oligomeric rings. This is conveniently done by means of modern analytical techniques such as gas-liquid and gel-permeation chromatography (Semiyen, 1976). 

Polysiloxanes are known to be chemically and thermally stable. Due to this feature they can be used as stationary liquids in gas chromatography (3,4, 5). ... 

The same is true for the chiral polysiloxanes described here. Their use as stationary phases in gas chromatography allows the calculation of the differences in enthalpy and entropy for the formation of the diaste-reomeric association complexes between chiral receptor and two enantiomers from relative retention time over a wide temperature range. Only the minute amounts of the polysiloxanes required for coating of a glas capillary are necessary for such determinations. From these numbers further conclusions are drawn on the stereochemical and environmental properties required for designing systems of high enantio-selectivity in condensed liquid systems. 

Chromatographic separations frequently rely upon interactions between analytes in a flowing liquid or gas stream (or mobile phase) and a solid surface which remains motionless. In traditional forms of chromatography, the motionless solid surface, or stationary phase, might be porous particles of a polar material like silica (a normal-phase chromatographic support), hydrophobically modified or coated silica (a reversed-phase chromatographic support), or a thin polysiloxane film on the inner lumen of a capillary (for capillary gas chromatography). 

Both gas/solid adsorption and gas/liquid partition chromatography can be used for GC-MS, but GC is by far the most common. Because, in GC, the stationary phase is a liquid, usually a polymer, its vapor pressure will cause a continual low flow, or bleed into the ion source of the mass spectrometer. This bleed, which usually consists of decomposed stationary phase, will produce a spectrum whose intensity increases with column temperature. Stationary phases should therefore be of the high-boiling, low-bleed type. Most currently used stationary phases for routine GC-MS are based on alkyl-polysiloxanes or alkyl-phenyl-polysiloxanes that are chemically bonded to the column wall to increase stability. Columns containing such phases can, in some cases, be used at temperatures of up to 400°C. One advantage, however, to the presence of bleed peaks in the spectrum is that they enable a continual check to be made on the mass spectrometer calibration. For the alkyl siloxanes, ion peaks are present, in decreasing relative abundance, at miz 73, 207, 281, 355, 429,... 

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