126 Electrophoresis 2013, 34, 126–140 Junjie Ou 1 Hui Lin 1,2 Zhenbin Zhang 1,2 Guang Huang 1,3 Jing Dong 1 Hanfa Zou 1 1 CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R & A Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CAS), Dalian, China 2 Graduate School of Chinese Academy of Sciences, Beijing, China 3 Dalian University of Technology, Dalian, China Received June 29, 2012 Revised October 13, 2012 Accepted October 13, 2012 Review Recent advances in preparation and application of hybrid organic-silica monolithic capillary columns Hybrid organic-silica monolithic columns, regarded as a second generation of silica-based monoliths, have received much interest due to their unique properties over the pure silica- based monoliths. This review mainly focuses on development in the fields of preparation of hybrid monolithic columns in a capillary and their application for CEC and capillary liquid chromatography separation, as well as for sample pretreatment of solid-phase microex- traction and immobilized enzyme reactor since July 2010. The preparation approaches are comprehensively summarized with three routes: (i) general sol–gel process using tri- alkoxysilanes and tetraalkoxysilanes as coprecursors; (ii) “one-pot” process of alkoxysilanes and organic monomers concomitantly proceeding sol–gel chemistry and free radical poly- merization; and (iii) other polymerization approaches of organic monomers containing silanes. The modification of hybrid monoliths containing reactive groups to acquire the desired surface functionality is also described. Keywords: Monolithic columns / Organic-silica hybrid materials / Ring-opening polymeriza- tion / Sol–gel DOI 10.1002/elps.201200344 1 Introduction During the last two decades, several advancements have been made in the chromatographic columns for separation sci- ences. Due to its key role in the separation process, the col- umn is rightfully considered as the heart of the separation sys- tem, particularly, covering GC, HPLC, capillary liquid chro- matography (CLC), and CEC and so on. Although the family of columns has continuously enlarged, researchers continue to pursue new columns to broaden their applications. Mono- lithic columns possess a unique structure and exhibit some Correspondence: Dr. Junjie Ou, CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R & A Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CAS), Dalian 116023, China E-mail: junjieou@dicp.ac.cn Fax: +86-411-84379620 Abbreviations: AA, amino acid; AIBN, a,a’- azobisisobutyronitrile; APTES, aminopropyltriethoxysilane; C8-TES, n-octyltriethoxysilane; CLC, capillary liquid chro- matography; GPTMS, glycidoxypropyltrimethoxysilane; IMER, immobilized enzyme reactor; MAA, methacrylic acid; MIP, molecularly imprinted polymer; MPTMS, 3- mercaptopropyltrimethoxysilane; MTMS, methyltriethoxysi- lane; NHSG, non-hydrolytic sol–gel; POSS, polyhedral oligomeric silsesquioxane; PSG, photopolymerized sol– gel; PTES, phenyltriethoxysilane; SPME, solid-phase mi- croextraction; TEOS, tetraethoxysilane; TMOS, tetram- ethoxysilane; VTMS, vinyltrimethoxysilane; -MAPS, - methacryloxypropyltrimethoxysilane exceptional characteristics, which are regarded as new genera- tion of stationary phases. Their much higher external porosity compared to conventional particle-packed columns minimize the pore diffusion and mass transfer resistance, resulting in higher permeability and low-pressure drop with higher sep- aration efficiency [1–4]. As a result, monolithic columns be- come an excellent tool in the analytical laboratory, not only for separation fields covering RP, ion-exchange, hydrophilic interaction, size exclusion, and affinity chromatography etc., but also for sample preparation including SPE or solid-phase microextraction (SPME), and as basis for immobilized en- zyme reactors (IMERs) [5–11]. To date, two most common monolithic materials used for columns are the organic polymers such as polymethacry- lates, polyacrylamide, and polystyrenes, and the silica-based inorganic polymers. The former monoliths can be generally prepared by in situ polymerization of organic monomers and crosslinkers in the presence of porogenic solvents, and the latter ones may be fabricated via a sol–gel process following a chemical modification of the matrix with different silylation reagents. They therefore exhibit different advantages and dis- advantages. A number of review articles have been published in the last decade describing progresses on their preparations, properties, and applications [12–18]. It can be easily found that the problems of both the swelling or shrinkage of organic ∗ Additional corresponding author: Professor Hanfa Zou, E-mail: hanfazou@dicp.ac.cn Colour Online: See the article online to view Figs. 1 and 8 in colour. C  2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.electrophoresis-journal.com