NaDDBs as a Dispersion Agent for Multi-Walled Carbon Nanotubes in Capillary Electrophoretic Separation of Nucleotides
Date Issued
2009
Date
2009
Author(s)
Hsieh, Yu-Fang
Abstract
Carbon nanotubes (CNTs) belong to the fullerene family of carbon allotropes. The walls of the tubes consist of hexagonal carbon, and the end caps contain pentagonal rings. Their specific physical properties, such as high surface areas and mechanical and electrical properties, make CNTs interesting to analytical science. In our work, a special type of MEKC, NaDDBs-coated MWCNTs EKC was used for the separation of biomolecules. Sodium dodecylbenzenesulfonate (NaDDBs) was used for the dispersion of carbon nanotubes. NaDDBs is composed of two parts: the long hydrophobic chain and the benzylsulfonate group. In comparison with the conventional surfactant used in MEKC, sodium dodecylsulfate (SDS), NaDDBs suspends more MWCNTs (about 100-fold) than SDS, and the π-π interaction between the benzene ring of NaDDBs and MWCNTs prolongs the slurry suspension time. Using NaDDBs as surfactant can reduce the required amount of MWCNTs and decrease the baseline noise. Even the system without micelle could make the good pseudostationary phase. To produce a stable suspension, various ratios (w/w) of MWCNTs to NaDDBs over the range from 1:10 to 1:20 were studied with turbidimetry. The ratio of 1:10 produces the most stable form. Considering this, several parameters affecting the CE separation were studied, including the amount of surfactant and of MWCNTs, the buffer pH, composition and concentration, as well as the organic modifier. The results show that 8 mg L-1 of NaDDBs-coated MWCNTs (0.8 mg/L) as the pseudostationary phase in a phosphate buffer (30 mM, pH 8) as the mobile phase could provide the best recognition for 7 nucleoside monophosphates, baseline separating even the geometric isomers. In the stacking mode, adding 10% MeOH to the sample mixture in a phosphate buffer (50 mM, pH 9) containing 0.8 mg L-1 MWCNTs and 8 mg L-1 NaDDBs, 12 model compounds, including nucleoside mono-, di- and tri-phosphates, were resolved. The nucleotides with a more electron-withdrawing functional group have a strong interaction with MWCNTs because of the π electron donor and π electron acceptor interaction. From the retention behavior of each analyte, the separation mechanism was suggested to be hydrogen bonding and a hydrophilic interaction between surfactant and analytes, as well as hydrophobic force and π-π interaction between MWCNTs and nucleotides, in addition to the electrophoretic mobility difference.
Subjects
carbon nanotubes
sodium dodecylbenzenesulfate
MWCNT
suspension
nucleotides
Type
thesis
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