Confocal Raman Microscopy of the Interfacial Regions of Liquid Chromatographic Stationary-Phase Materials

Gasser-Ramirez, Jennifer L.; Harris, Joel M.

doi:10.1021/ac802541p

Cited by 18 publications

(28 citation statements)

References 54 publications

(94 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The interfacial environment of the alkyl-bonded silica in contact with water–organic mixtures has been studied by nuclear magnetic resonance (NMR), − infrared, , and Raman spectroscopy. − These studies suggested that the concentration of the organic solvent at the surface of the alkyl-bonded layer is significantly greater than that of the bulk solution phase. RPLC itself is also an effective method to investigate the interfacial environment and solute accumulation behavior at the aqueous/alkyl-bonded silica interface.…”

Section: Introductionmentioning

confidence: 99%

Effect of Acetonitrile on the Solute Distribution at the Heterogeneous Interface Region between Water and Hydrocarbonaceous Silica Revealed by Surface-Bubble-Modulated Liquid Chromatography

et al. 2018

View full text Add to dashboard Cite

The interface between water and a hydrocarbonaceous material is important because of its usefulness for separation of a variety of chemical compounds. In order to change the magnitude of accumulation of the compounds at the water/hydrophobe interface, water miscible organic solvents such as acetonitrile are often added to the aqueous solution. However, the origin of the effect of the organic solvents on the separation of solute compounds has not been fully elucidated. We used surface-bubble-modulated liquid chromatography to investigate the spatial distribution of various organic compounds on an alkyl-bonded silica in contact with an acetonitrile–water mixture (0–5% (v/v)). Our results show that the dependences of the bulk liquid-to-aqueous/alkyl chain interface and bulk liquid-to-alkyl bonded layer distribution coefficients for organic compounds on acetonitrile concentration in aqueous solution are quite different from each other. It has been revealed that acetonitrile slightly partitions into the interior of the alkyl chain layer, whereas it preferentially accumulates at the interface although the interfacial liquid layer at the interface consists of not only acetonitrile but also water. The addition of acetonitrile to the aqueous solution causes a distinct decrease of accumulation of the compounds having hydrophilic groups, while the change in retention of hydrophobic compounds is rather small.

show abstract

Section: Introductionmentioning

confidence: 99%

Effect of Acetonitrile on the Solute Distribution at the Heterogeneous Interface Region between Water and Hydrocarbonaceous Silica Revealed by Surface-Bubble-Modulated Liquid Chromatography

et al. 2018

View full text Add to dashboard Cite

show abstract

“…To determine the organization of lipid layers deposited onto the interior surfaces of reversed-phase chromatographic silica, it is helpful to have an in situ spectroscopic measurement of lipid bilayer structure. Raman spectroscopy has previously been employed in situ to probe the composition and structure of reversed-phase chromatographic interfaces, − and this approach was recently used in a confocal-microscopy experiment to probe the structure of hybrid lipid bilayers formed within individual chromatographic silica particles . Confocal Raman microscopy is well suited to this task because it can probe the internal interfacial composition and structure within individual chromatographic particles; the results showed that the acyl chains of the phospholipid indeed interact with the C 18 alkyl chains bound to the silica surface, as suggested by Tsirkin and Grushka .…”

mentioning

confidence: 97%

Confocal Raman Microscopy Investigation of Self-Assembly of Hybrid Phospholipid Bilayers within Individual Porous Silica Chromatographic Particles

2019

Self Cite

View full text Add to dashboard Cite

Hybrid-supported phospholipid bilayers are a model structure utilized for measurement of molecular interactions that typically occur at cell membranes. These membrane models are prepared by adsorption of a lipid monolayer onto a stable n-alkyl chain layer that is covalently bound to a support surface. Hybrid bilayers have been adapted to chromatographic retention measurements of lipophilicity through the assembly of a phospholipid monolayer onto n-alkane-modified silica surfaces in reversed-phase chromatographic particles. Recent Raman microscopy studies of these particles have shown that the acyl chains of the phospholipid interact with the C18-alkyl chains immobilized on the silica surface, where both lipid and C18 alkyl chains become ordered because of chain interdigitation. Confocal Raman microscopy has also been used to investigate the association of small molecules with hybrid-lipid bilayers in C18 chromatographic silica particles; the partitioning of model solutes compares favorably to that in lipid vesicle membranes with similar changes in acyl-chain structure (disordering) with solute partitioning. The present study seeks information about how these membrane-mimetic bilayers assemble onto the C18-derivatized silica surfaces of reversed-phase chromatographic silica particles. Confocal Raman microscopy is capable of interrogating the time-dependent internal composition and structure within individual silica particles. The Raman scattering data can be resolved into component Raman spectra and corresponding composition vectors that describe the time-dependent changes in intensity of the component spectra. This analysis provides insight into how the structures of both the lipid and C18 alkyl chains of hybrid lipid bilayers evolve during deposition and organization on the internal surfaces of reversed-phase chromatographic silica particles.

show abstract

“…23 Confocal Raman microscopy within individual reversed-phase chromatographic particles has been used to measure solid-phase extraction of pyrene into surface-bound C 18 chains 23 and liquid−liquid (octanol−water) partitioning of naphthoic acid over a range of source-phase pH. 24 Raman spectroscopy has been utilized previously to measure partitioning of trace organics into polydimethylsiloxane matrixes, 25 and within-particle confocal Raman microscopy has been used to study silica surface functionalization, 26 solvation of the C 18 stationary phase environment, 27,28 and to investigate the mechanism of surfactant-mediated retention in ion-interaction chromatography. 29 Despite correlations between hybrid-bilayer retention in chromatographic experiments and membrane partitioning, confocal-Raman microscopy measurements have shown that hybrid bilayers formed in reversed-phase chromatographic particles are interdigitated, with the acyl chains from the upper leaflet extending into the lower leaflet of C 18 chains.…”

mentioning

confidence: 99%

“…Confocal Raman microscopy within individual reversed-phase chromatographic particles has been used to measure solid-phase extraction of pyrene into surface-bound C 18 chains and liquid–liquid (octanol–water) partitioning of naphthoic acid over a range of source-phase pH . Raman spectroscopy has been utilized previously to measure partitioning of trace organics into polydimethylsiloxane matrixes, and within-particle confocal Raman microscopy has been used to study silica surface functionalization, solvation of the C 18 stationary phase environment, , and to investigate the mechanism of surfactant-mediated retention in ion-interaction chromatography …”

mentioning

confidence: 99%

Confocal Raman Microscopy for in Situ Measurement of Phospholipid–Water Partitioning into Model Phospholipid Bilayers within Individual Chromatographic Particles

2018

Self Cite

View full text Add to dashboard Cite

The phospholipid-water partition coefficient is a commonly measured parameter that correlates with drug efficacy, small-molecule toxicity, and accumulation of molecules in biological systems in the environment. Despite the utility of this parameter, methods for measuring phospholipid-water partition coefficients are limited. This is due to the difficulty of making quantitative measurements in vesicle membranes or supported phospholipid bilayers, both of which are small-volume phases that challenge the sensitivity of many analytical techniques. In this work, we employ in situ confocal Raman microscopy to probe the partitioning of a model membrane-active compound, 2-(4-isobutylphenyl) propionic acid or ibuprofen, into both hybrid- and supported-phospholipid bilayers deposited on the pore walls of individual chromatographic particles. The large surface-area-to-volume ratio of chromatographic silica allows interrogation of a significant lipid bilayer area within a very small volume. The local phospholipid concentration within a confocal probe volume inside the particle can be as high as 0.5 M, which overcomes the sensitivity limitations of making measurements in the limited membrane areas of single vesicles or planar supported bilayers. Quantitative determination of ibuprofen partitioning is achieved by using the phospholipid acyl-chains of the within-particle bilayer as an internal standard. This approach is tested for measurements of pH-dependent partitioning of ibuprofen into both hybrid-lipid and supported-lipid bilayers within silica particles, and the results are compared with octanol-water partitioning and with partitioning into individual optically trapped phospholipid vesicle membranes. Additionally, the impact of ibuprofen partitioning on bilayer structure is evaluated for both within-particle model membranes and compared with the structural impacts of partitioning into vesicle lipid bilayers.

show abstract

Confocal Raman Microscopy of the Interfacial Regions of Liquid Chromatographic Stationary-Phase Materials

Cited by 18 publications

References 54 publications

Effect of Acetonitrile on the Solute Distribution at the Heterogeneous Interface Region between Water and Hydrocarbonaceous Silica Revealed by Surface-Bubble-Modulated Liquid Chromatography

Effect of Acetonitrile on the Solute Distribution at the Heterogeneous Interface Region between Water and Hydrocarbonaceous Silica Revealed by Surface-Bubble-Modulated Liquid Chromatography

Confocal Raman Microscopy Investigation of Self-Assembly of Hybrid Phospholipid Bilayers within Individual Porous Silica Chromatographic Particles

Confocal Raman Microscopy for in Situ Measurement of Phospholipid–Water Partitioning into Model Phospholipid Bilayers within Individual Chromatographic Particles

Contact Info

Product

Resources

About