Takeshi Hara - Speaker

Yoshihiro Izumi - Contributor

Motonao Nakao - Contributor

Gino Baron - Contributor

Takeshi Bamba - Contributor

Gert Desmet - Contributor

Over the past decades, the open-tubular column format has received a lot of attention as a separation medium for liquid chromatography, because of its ability to combine high column efficiency with high column permeability. In a proceeding study on this column format, we have shown that it is possible to prepare porous-layered open tube (PLOT) columns with a controlled layer thickness and mesoporosity in fused-silica capillaries with 5 μm inner diameter (i.d.) via sol-gel processing, to enhance the retention and the sample loadability. In the present study, we address the preparation and examination of hybrid PLOT columns, aiming at enhancing the hydrophobic ability by introducing methyl groups with methyltrimethoxysilane (MTMS) as silica precursor.

PLOT columns were produced with a mixture of 85:15 (v/v) tetramethoxysilane (TMOS)/MTMS, urea, polyethylene glycol with a molecular weight of 20 000 g/mol, and 0.01 M aqueous acetic acid solution. After the preparation, the PLOT columns were functionalized with octadecyldimethyl-N,N-dimethylaminosilane, and subsequently with 1-(trimethylsilyl)-1H-imidazol for endcapping. Afterwards, the column performance of the functionalized PLOT columns was
assessed with coumarin dyes by fluorescence detection, using 70:30 (v/v) methanol/water as mobile phase. Moreover, scanning electron microscopy (SEM) was employed to visualize the resulting structures.

SEM images showed that it is possible to control the layer thickness by varying the amount of silica precursors in the feed solution. We also found that hybrid PLOT columns can provide an increase in volumetric phase ratio (m) compared to TMOS-based PLOT columns prepared with a nearly-same molar quantity of silica precursor. For the chromatographic performance, hybrid columns could provide approximately 60% larger retention factor (k) for coumarin C460 and
C480 than TMOS-based columns prepared with the similar molar quantity. Testing 35 cm-hybrid columns provided H = 3.4−3.9 μm for C480 at an optimal linear velocity of u0 = 0.6 mm/s, and showed that the data on reduced plate height curves is well-fitted with Golay-Aris theory as well as the TMOS-based columns used in our previous study. When we extended the columns length to 1.2─1.3 m, the inherent column properties, such as retention- and reduced plate height-values, were maintained. Comparison of column efficiency of hybrid columns to that of TMOS-based columns under similar retention condition suggested that insertion of the functional groups to porous silica layer
with silica precursor could be beneficial to enhance retention ability while keeping thin layer thickness to provide high column efficiency.
25 Sep 2018

Event (Conference)

Title32nd International Symposium on Chromatography (ISC 2018)
Abbrev. TitleISC 2018
Web address (URL)
Degree of recognitionInternational event

ID: 39952542