Sol−Gel Monolithic Columns with Reversed Electroosmotic Flow for Capillary Electrochromatography

Abstract

Sol-gel chemistry was used to prepare porous monolithic columns for capillary electrochromatography. The developed sol-gel approach proved invaluable and generates monolithic columns in a simple and rapid manner. Practically any desired column length ranging from a few tens of centimeters to a few meters may be readily obtained. The incorporation of the sol-gel precursor, N-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, into the sol solution proved to be critical as this reagent possesses an octadecyl moiety that allows for chromatographic interactions of analytes with the monolithic stationary phase. Additionally, this reagent served to yield a positively charged surface, thereby providing the relatively strong reversed electroosmotic flow (EOF) in capillary electrochromatography. The enhanced permeability of the monolithic capillaries allowed for the use of such columns without the need for modifications to the commercial CE instrument. There was no need to pressurize both capillary ends during operation or to use high pressures for column rinsing. With the developed procedure, no bubble formation was detected during analysis with the monolithic capillaries when using electric field strengths of up to 300 V cm(-1). The EOF in the monolith columns was found to be dependent on the percentage of organic modifier present in the mobile phase. Separation efficiencies of up to 1.75 x 10(5) plates/m (87,300 plates/column) were achieved on a 50 cm x 50 microm i.d. column using polycyclic aromatic hydrocarbons and aromatic aldehydes and ketones as test solutes.

Capillary Electrochromatography on Monolithic Silica Columns

“…14 Continuous silica columns in a capillary have been reported for use in CEC as well as in HPLC. [15][16][17] The column efficiency of these monolithic columns was generally lower than that reported with columns packed with small silica particles. 18 Ishizuka and coworkers prepared a continuous silica gel from tetramethoxysilane using a sol-gel process in a fused-silica capillary.…”

Recent advances in preparation and application of hybrid organic‐silica monolithic capillary columns

“…As shown in Fig. 3, trialkoxysilanes with hydrophobic organic moieties, such as N-octadecyldimethyl [3-(trimethoxy silyl)propyl]ammonium chloride [23], n-octyltriethoxysilane (C8-TES) [32][33][34][35], phenyltriethoxysilane (PTES) [36][37][38], propyltrimethoxysilane (C3-TMS) [39], MTMS [40][41][42][43][44], and other trialkoxysilanes with active organic functionalities, such as aminopropyl triethoxysilane (APTES) [45][46][47][48][49], N-(␤-aminoethyl)-␥-aminopropyl-triethoxysilane [50], N-(␤-aminoethyl)-␥-aminopropylmethyldimethoxysilane [51], 3-chloropropyltrimethoxysilane [52], 3-mercaptopropyltrime thoxysilane (MPTMS) [53], N-trimethoxysilylpropyl-N,N,Ntrimethylammonium chloride [54], allyl-trimethoxysilane [ 55,56], and vinyltrimethoxysilane (VTMS) [57] have been selected as coprecursors with tetraalkoxysilanes, TMOS, or TEOS. Additionally, bridged silanes such as 1,4-bis(triethoxysily1)benzene [58] have also been used for preparation of hybrid monoliths.…”

Synthesis of boronate-silica hybrid affinity monolith via a one-pot process for specific capture of glycoproteins at neutral conditions

“…With the unique properties of simplicity of preparation, rapid mass-transfer rate, low backpressure, and versatile surface modification, monolithic materials have been more and more attractive and widely used in proteomic analysis [21,22]. Since Malik et al [23] first prepared a C 18 -incorprated hybrid monolith, the organic-silica hybrid monolith has drawn more attentions in the separation field [24,25], which combines the advantages of both organic monolith and inorganic monolith, such as easily fabricated, less shrinkage and good pH stability. A "one-pot" approach was developed for preparation of organic-silica hybrid capillary monolithic columns by concurrently introducing organic monomers and alkoxysilanes.…”