Journal
JOURNAL OF CHROMATOGRAPHY A
Volume 1216, Issue 18, Pages 3857-3863Publisher
ELSEVIER
DOI: 10.1016/j.chroma.2009.02.070
Keywords
Hybrid silica monoliths; Nano-liquid chromatography; Capillary electrochromatography
Funding
- Research National Agency (ANR) [ANR-07-PCVI-0036-01]
- Agence Nationale de la Recherche (ANR) [ANR-07-PCVI-0036] Funding Source: Agence Nationale de la Recherche (ANR)
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Several modifications of a previously described protocol are proposed to improve the performances of in-situ synthesized C-8 hybrid silica monoliths. Our attention was focused on reducing the sources of radial heterogeneity that may be responsible for the poor efficiencies observed in the hydrodynamic elution mode. It was demonstrated that a decrease in the temperature of the capillary during the filling step equally to that of the polymerization mixture (0 degrees C), associated with a decrease of the gelation temperature to 20 degrees C along with a new pre-treatment of the capillary's internal walls [with a mixture of tetraethoxysilane (TEOS)/EtOH (1/3, v/v)] allows (i) increasing the radial homogeneity of the monolith, thus further enhancing the performances in the nano-liquid chromatography (nano-LC) mode, (ii) improving the capillary to capillary reproducibility in terms of permeability and efficiencies. In fact, the average minimum plate height H-min was lowered from 24 to 14 mu m and the capillary-to-capillary reproducibility of the synthesis was widely improved by factors two and three of reduction on the calculated standard deviation, respectively for both the efficiency in the nano-LC mode and the permeability. At last, the improved radial homogeneity and anchoring of the synthesized monoliths allowed increasing the inner diameter of the capillary (up to 150 mu m) without any significant loss in efficiency. Finally, long term stability of the as-obtained monolithic stationary phases in terms of retention and efficiency was studied. In addition, the evaluation of their chromatographic behaviour was also achieved with the Tanaka test and the results were compared to those already published for commercial monoliths (Chromolith) as well as for particulate stationary phases. (C) 2009 Elsevier B.V. All rights reserved.
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