Investigation of Chromatographic Surface Viscosity Using Total Internal Reflection Fluorescence

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Abstract
Total internal reflection fluorescence (TIRF) spectroscopy was employed to determine the viscosity of planar chromatographic surfaces. Various n-alkyldimethylchlorosilanes were used to modify the surface of a UV-quartz plate, so as to obtain a covalently attached monomeric C1, C3, C8, or C18 surface. TIRF anisotropy data of 1, 6-diphenylhexatriene (DPH) were collected on the unmodified and modified surfaces in the presence of overlaying solvents covering a range of viscosities. The results indicate that DPH adsorbs onto C1 and C3, but clearly exhibits partitioning with the C18 phase. The C8 surface data indicate intermediate behavior between adsorption and partitioning. On the basis of these preliminary data, the estimated microviscosity of a planar C18 surface is approximately 18 cP.