We recently introduced a new method  to deposit carbon on fully porous silicas (5μm) to address some of the shortcomings of carbon clad zirconia (C/ZrO 2), which has rather low retention due to its low surface area (20-30m 2/g). The method enables the introduction of a thin, homogeneous layer of Al(III) on silica to serve as catalytic sites for carbon deposition without damaging the silica's native pore structure. Subsequent carbon deposition by chemical vapor deposition resulted in chromatographically useful carbon phases as shown by good efficiencies and higher retentivity relative to C/ZrO 2. Herein, we use the above method to develop a novel carbon phase on superficially porous silica (2.7μm). This small, new form of silica offers better mass transfer properties and higher efficiency with lower column back pressures as compared to sub 2μm silica packings, which should make it attractive for use as the second dimension in fast two-dimensional LC (LC×LC). After carbon deposition, several studies were conducted to compare the new packing with C/ZrO 2. Consistent with work on 5μm fully porous silica, the metal cladding did not cause pore blockage. Subsequent carbon deposition maintained the good mass transfer properties as shown by the effect of velocity on HETP. The new packing exhibits efficiencies up to ∼5.6-fold higher than C/ZrO 2 for polar compounds. We observed similar chromatographic selectivity for all carbon phases tested. Consequently, the use of the new packing as the second dimension in fast LC×LC improved the peak capacity of fast LC×LC. The new material gave loading capacities similar to C/ZrO 2, which is rather as expected based on the surface areas of the two phases.
Bibliographical noteFunding Information:
The authors would like to thank Prof. Dwight Stoll of Gustavus Adophus College for many helpful conversations. This work was supported by a grant from the National Institute of Health ( GM 54585-15 ). We also wish to acknowledge Agilent Technologies and ZirChrom Separations Inc. for the gifts of columns. M.F. acknowledges a fellowship from ANPCyT-UNLP (Argentina).
- Carbon clad silica
- Stationary phase
- Superficially porous particle
- Two-dimensional LC