Lateral Diffusion of Molecules Partitioned into Silica-Bound Alkyl Chains:  Influence of Chain Length and Bonding Density

Hansen, Richard L.; Harris, Joel M.

doi:10.1021/ac960119j

Cited by 38 publications

(30 citation statements)

References 59 publications

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“…A comparative study [164] has reported the short range effect of run time on the column parameter of different high or low grafted reversed phases. In order to assert that C22 and C30 bondages give best peak symmetry, they must be evaluated with the same based silica, the same bondage density [168] and in such a way that the stereochemical state of the stationary phase is the same, i.e. Thus, it can be argued that longer alkyl chains will interact preferentially with each other, forming overlapping chains that restrict the access of the surface silanols [165,166].…”

Section: 22amentioning

confidence: 99%

Silica and other materials as supports in liquid chromatography. Chromatographic tests and their importance for evaluating these supports. Part I

et al. 2001

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Reversed-phase liquid chromatography (RP-HPLC) has become a powerful and widely employed technique in the separation and analysis of a great variety of compounds with different functionalities. The most common type of stationary phase for RP-HPLC consists of nonpolar, hydrophobic organic species (e.g., octyl, octadecyl) attached by siloxane bonds to the surface of a silica support. In the first part of this article, a description of the many beneficial properties that make porous silica the most employed support in RP-HPLC will be presented, starting from the synthesis of silica. It is noteworthy that the chromatographic properties of the final column are strictly correlated to the preparation type. A silica surface possesses a number of attractive properties, but also some drawbacks. Unreacted or residual silanols interact with basic compounds and can induced peak tailing, which means a loss in chromatographic performance. This problem has lead many manufactures to produce stationary phases with reduced silanol activity which improve dramatically the peak shape of basic compounds. In the second part of this review, different approaches are proposed to obtain less reactive stationary phases

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Section: 22amentioning

confidence: 99%

Silica and other materials as supports in liquid chromatography. Chromatographic tests and their importance for evaluating these supports. Part I

et al. 2001

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“…[9][10][11] Lateral diffusion is measured very accurately by either fluorescence recovery after photobleaching [4][5][6][7][8][12][13][14] or fluorescence correlation spectroscopy, [15][16][17][18] where the latter avoids perturbing the sample. The interpretation of the results is most straightforward when there is a single diffusing species; however, the data can, in principle, be analyzed for multiple species.…”

Section: Introductionmentioning

confidence: 99%

Single-Molecule Study of an Adsorbed Oligonucleotide Undergoing Both Lateral Diffusion and Strong Adsorption

Wirth

Swinton

2001

J. Phys. Chem. B

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Single-molecule fluorescence spectroscopy was used to probe the lateral transport of an adsorbed oligonucleotide, the SP6 promoter primer, which is a 24-mer labeled at the 5′ end with tetramethylrhodamine. The oligonucleotide was adsorbed to the interface of an aqueous solution of 0.01 M KCl and silica chemically modified by chlorodimethyloctadecylsilane. Confocal fluorescence microscopy achieved single-molecule resolution, with a molecule in the beam 7% of the time. Autocorrelation of the data fit well to a model having two species, one diffusing and the other one undergoing transient strong adsorption. A small number of bursts, 0.3%, had unusually long durations, accounting for the slow component in the autocorrelation. When these long bursts were excised from the data, the autocorrelation fit well to simple diffusion, with D ) 4 × 10 -6 cm 2 /s. Autocorrelation of the long bursts alone gave a rate constant for desorption of 3 s -1 . The strongly adsorbed molecules were found to comprise 10% of the total population of adsorbates. It is concluded that the lateral transport of the SP6 promoter primer is described by fast lateral diffusion interrupted by rare, reversible, strong adsorption to defect sites. During strong adsorption, the tetramethylrhodamine label undergoes hindered motion, suggesting it is not the adsorbing moiety.

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“…Regarding retention in RPLC and its dependence on conformational order, in general, the highest degree of shape selectivity [16,47,48] and retention [49,50] are observed for the most ordered stationary phase. However, controversy can also be found with respect to this issue.…”

Section: Resultsmentioning

confidence: 97%

Reverse-High Performance Liquid Chromatography Mechanism Explained by Polarization of Stationary Phase

Andrade-Eiroa¹

2011

CheM

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Original results and conclusions on Reverse Phase High Performance Liquid Chromatography (RPLC) mechanism are here presented. So far, none of the theoretical approaches applied to the RPLC mechanism can explain the retention and elution mechanisms of most of the analytes by RPLC, especially neutral organic compounds. Our experiences allowed us to state that RPLC retention mechanism most likely occurs through polarization of stationary phase (usually dielectric surfaces) submerged into solvents with huge dielectric constant and high dipole moment (i.e. water and/or acetonitrile) at high pressures as those applied in RPLC systems. The surface polarized interacts with polarizable target analytes (i.e. naphthalene, pyrene or benzo(ghi)perylene) in such a way that the retention depends on the medium polarizability of the target compound. The higher is the medium polarizability of the compound retained the higher is its retention time.By using Polycyclic Aromatic Hydro-carbons (PAHs) and 6-nitrochrysene as probes, we found that although the dependence of retention times on pressure is not evident in most cases, the interaction between pressure and the mobile phase dipole moment is evidenced at the light of the constructed mathematical models. Two very different cases can be distinguished:1. On one hand, when low dipole moment mobile phases are used, high pressure means big work developed by the system in such a way that high pressures inside the system reduce retention times compared to low pressures.2. On the another one, when high dipole moment solvents are used as mobile phase, high pressure entails an outstanding increase of the retention times compared to low dipole moment mobile phases. This is most likely due to high pressures that entail closer alignment of mobile phase dipoles and lesser tilt of them, originating an outstanding electric field inside the analytical column.In addition to this, reduced retention times for dipole solutes (6-nitrochrysene, dipole molecule) compared to non-polar solutes (PAHs) were observed when pressure drops. This conclusions would allow to extend the model to basic/acid molecules at different pH. In this case, electrostatic repulsions among analyte molecules should be considered.

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Lateral Diffusion of Molecules Partitioned into Silica-Bound Alkyl Chains: Influence of Chain Length and Bonding Density

Cited by 38 publications

References 59 publications

Silica and other materials as supports in liquid chromatography. Chromatographic tests and their importance for evaluating these supports. Part I

Silica and other materials as supports in liquid chromatography. Chromatographic tests and their importance for evaluating these supports. Part I

Single-Molecule Study of an Adsorbed Oligonucleotide Undergoing Both Lateral Diffusion and Strong Adsorption

Reverse-High Performance Liquid Chromatography Mechanism Explained by Polarization of Stationary Phase

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