Raman spectroscopy stationary phases

Liao, Z.H., Orendorff, C.J., Sander, L.C., and Pemberton, J.E., Structure-function relationships in high-density docosylsUane bonded stationary phases by Raman spectroscopy and comparison to octadecylsUane bonded stationary phases. Anal. Chem., 78,5813, 2006. 

Doyle, C.A., Vickers, T.J., Mann, C.K., and Dorsey, J.G, Characterization of hqnid chromatographic stationary phases by Raman spectroscopy—effects of ligand type, J. Chromatogr. A, 779, 91, 1997. 

Ho, M., Cai, M., and Pemberton, J.E., Characterization of octadecylsilane stationary phases on commercially available silica-based packing materials by Raman spectroscopy. Ana/. Chem., 69, 2613, 1997. 

The fullerenes, Cgo and C70, are produced in the laboratory by the contact arc-evaporation of 6 mm graphite rods (e.g. Johnson Matthey, spectroscopic grade) in 100 torr of helium in a water-cooled stainless steel chamber described previously [5]. The soluble material in the soot produced from the arc-evaporation is extracted with toluene using a Soxhlet apparatus. The pure fullerenes are obtained by chromatography on neutral alumina columns using hexanes as the eluant, or by the use of a simple filtration technique using charcoal-silica as the stationary phase and toluene as the eluant [5]. The fullerenes so prepared are characterized by UV/Vis spectroscopy and other techniques. FT-IR spectra of vacuum deposited fullerene films on KBr crystals also provide a means of characterization, just as do Raman spectra of films deposited on a silicon crystal. Ultraviolet and X-ray photoelectron spectra of fullerene films on... 

Standardless analysis, 323 Standards, in calibration, 11, 17 States, virtual, 495,606 in laser media, 171 in Raman spectroscopy, 482,484 Stationary phase, 762 chiral, 806, 837... 

To determine the role of stationary phase structure in the retention process, it is of primary importance to understand its structure in various solvent environments. Studies of the interphase region using deuterium NMR have shown that it is the mobile phase composition that determines the structure of the stationary phase (d). Results have shown that water does not associate strongly wdth the alkyl chains. However, acetonitrile can associate strongly, even at low mole fractions because of the microheterogeneous environments that exist for the binary mixture. Previous in situ studies of the alkyl stationary phases using surface enhanced Raman spectroscopy have also concluded that little conformational change occurs with the addition of a polar solvent to the interface (7). 

This lack of solvent-induced monolayer disorder was also observed by Pemberton and coworkers (7). Pemberton and coworkers used Raman spectroscopy to examine Cis alkylsiloxane monolayers on a SiQ/Ag substrate and found little disruption of the alkyl chains in contact with acetonitrile, as well as water. The results of Carr and Harris (19), however, showed that a Cis chromatographic stationary phase assumes a collapsed structure in water. The stationary phase can evolve from this collapsed state with the addition of an organic modifier, such as acetonitrile, to the aqueous solvent. The modifier intercalates into the monolayer, causing an increase in volume, polarity, and alkyl chain order. 

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