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Synthesis of propyl‐functionalized hybrid monolithic silica capillaries and evaluation of their performances in nano‐LC and CEC
Author(s) -
Roux Richard,
Puy Guillaume,
Demesmay Claire,
Rocca JeanLouis
Publication year - 2007
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200700304
Subject(s) - monolith , monolithic hplc column , hybrid material , chemistry , siloxane , capillary electrochromatography , chemical engineering , polymerization , in situ polymerization , polymer , matrix (chemical analysis) , ormosil , grafting , silanol , condensation polymer , sol gel , chromatography , organic chemistry , high performance liquid chromatography , catalysis , stationary phase , engineering
During the last decade, silica monolithic capillaries have focused more and more attention on miniaturized separation techniques like CEC, nano‐LC, and chip electrochromatography owing to their unique chromatographic properties and to their possible in situ synthesis. Nevertheless, the preparation of conventional silica‐based individual monolithic columns is time consuming, owing to the individual steps involved, including the synthesis of the silica matrix and its subsequent on‐column chemical grafting. The hybrid organic–inorganic monoliths, whose synthesis is based on the polycondensation of siloxane with organosiloxane precursors, seems to be an attractive alternative since their direct synthesis leads to silica monoliths with organic moieties covalently linked to the inorganic silica matrix through hydrolytically stable Si–C bonds. This study describes the synthesis of hybrid monoliths using propyltrimethoxysilane (C 3 ‐TriMOS) as a new kind of silica coprecursor to subsequently increase the hydrophobicity of the stationary phase. The influence of several experimental parameters (pH, gelation temperature, relative proportion of the precursors) on the textural (skeleton and macropore size) and chromatographic properties (efficiency, retention, and electroosmotic mobility) of the obtained monoliths are discussed. The results show that the optimal coprecursor incorporation is obtained after a postgelation step during which the condensation of the C 3 ‐TriMOS coprecursor is favored by an increase in the pH medium. Thermal hydrolysis of urea previously added to the polymerization mixture allows this in situ pH increase. These hybrid monoliths present hydrophobic properties and allow the separation of test mixtures in the RP mode without any further modification. Moreover, they present excellent efficiencies since reduced plate height as low as 5 and 15 μm are obtained in the electrodriven mode (CEC) and in the hydrodynamic one (nano‐LC), respectively.