A novel stationary phase based on amino derivatized nanotubes for HPLC separations: Theoretical and practical aspects

Abstract

A novel column based on silica containing immobilized carbon nanotubes (CNTs) was developed and evaluated in terms of its binding efficiency and resolution. First, CNT functionalized with amino groups (CNT-NH(2)) were prepared via chemical modification of carboxylic groups introduced on the CNT surface. Secondly the covalent immobilization of CNT-NH(2) was carried out by using glutardialdehyde activating agent on aminopropyl (AP)-silica surface. This CNT stationary phase was applied to the HPLC separation of two molecule series, i.e. polychlorinated biphenyl (PCB) isomers with different degrees of substitution in the ortho-position (non-ortho to tetra-ortho substituted) and terpenes (linalool, geraniol, thymol, alpha-terpineol). The retention behavior of these solute molecules was measured under isocratic conditions with different mobile phase compositions, ranging from 0.05-0.70 v/v of toluene in cyclohexane. The retention factors of the solute molecule do not depend linearly on the toluene fraction but follow a quadratic relationship. This CNT stationary phase was a very useful column for the separation of PCB congeners and terpenes. It was demonstrated that a planar conformation of the solute molecule enhanced the solute retention on this CNT stationary phase. As well, a quantitative structure relationship derived, demonstrated the significant input to retention was due to the structurally selective dipole-dipole and charge transfer interactions with the solutes. These results were compared with those obtained on the AP stationary phase. The proposed CNT stationary phase for the separation possess distinctive and interesting retentive properties, and chemometric analysis of retention data of appropriate designed series of test solutes appears to be a convenient, objective and quantitative method to prove a new phase specificity.

Incorporation of carbon nanotubes in porous polymer monolithic capillary columns to enhance the chromatographic separation of small molecules

“…Previous literature describing experiments with oxidized MWNT deposited within porous silica beads suggests that a high affinity of the immobilized nanotubes for aromatic compounds is the cause [63], however, a reduction in the column efficiency was also noted. Andre et al compared carbon nanotubes to a graphite sheet ( sp 2 carbon) rolled in a tube [42]. The π–π interaction at the large contact area are thought to be responsible for high retention of benzene derivatives.…”

Recent applications of carbon-based nanomaterials in analytical chemistry: Critical review

“…André et al [132] investigated the preparation and chromatographic characteristics of a silica column that was chemically-modified with amino groups, and then functionalized with CNT. In this work, the authors separated eight aromatic compounds and four terpenes, obtaining good resolution and reproducibility.…”

Development and Evaluation of a New Fluorinated Double-Wall Carbon Nanotube HPLC Stationary Phase

“…This increased can be attributed to specific polar fluorine-fluorine interactions which as well explained a better selectivity on the F-DWCNT stationary phase than on the DWCNT and C18 stationary phases. Also, since the nanotubes are full of π electrons the aromatic ring of each fluorobenzene molecule is likely to interact with the surface of tubes through = CH-π hydrogen bonds and π-π stacking [28] which explained the higher retention observed for the DWCNT and F-DWCNT columns when compared to the C18 column. The separation of a mixture of difluorophenols on the DWCNT and F-DWCNT stationary phases is given in Fig.…”

“…make them of particular interest in separation science [13,15]. For example, carbon nanotubes (CNTs) [16][17][18][19] were used in GC [20][21][22][23][24][25][26], HPLC [27][28][29][30][31][32][33][34][35], CE [36][37][38][39] and in capillary electrochromatography [40][41][42]. The interest of carbon nanotubes was that they could improve the analytical performances of the chromatographic methods such as higher resolution and chromatographic retention or better repeatability and stability due to the specific interactions between the analyte and the carbon nanotube (electrostatic Abstract A novel column based on silica-containing immobilized fluorinated double-wall carbon nanotubes (F-DWCNTs) was developed.…”