In a recent paper, Zheng and coworkers (J. Zheng, L. T. Taylor, J. D. Pinkston,and M. L
Chapter 29, Problem 29-11(choose chapter or problem)
In a recent paper, Zheng and coworkers (J. Zheng, L. T. Taylor, J. D. Pinkston,and M. L. Mangels, J. Chromatogr. A, 2005, 1082, 220) discuss the elution ofpolar and ionic compounds in SFC.(a) Why are highly polar or ionic compounds usuallv not eluted in SFC?(b) What types of mobile-phase additives have been' used to improve, the elutionof highly polar or ionic compounds? .(c) Why is ion-pairing SFC not often used?(d) Why arc ammonium salts sometimes added as mobile-phase modifiersin SFC?(e) The authors describe an SFC system that uses mass spectrometry (MS) as adetector. Discuss the interfacing of an SFC unit to a mass spectrometer. Comparethe compatibility of SFC with MS to that of HPLC and GC with MS.(f) The authors studied the effect of column outlet pressure on the elution ofsodium 4-dodecylbenzene sulfonate on three different stationary phaseswith five mobile-phase additives. What effect was observed, and what wasthe explanation for the effect?(g) What elution mechanisms were considered by thc authors?(h) Which mobile-phase additive gave the fastest elution of the sulfonate salts?Which provided the longest retention times?(i) Did a silica column give results similar to or different from a cyano bondedphasecolumn?
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