Solute Distribution Coupled with Laminar Flow in Wide-Bore Capillaries: What Can Be Separated without Chemical or Physical Fields?

Abstract

A number of researches have been devoted to the developments of novel separation principles and methodology, because material separation is one of the most important fundamentals in scientific and technological disciplines. In particular, flow separation methods, such as chromatography, 1,2 electrophoresis, [3][4][5][6][7] and field flow fractionation (FFF), [8][9][10] have been extensively used in various fundamental and practical fields, and have facilitated the advancements of modern science. These methods cover separation of almost all classes of materials. A number of dissolved molecules, from simple ions to macromolecules, can be separated by chromatography or electrophoresis, FFF and electrophoresis being capable of resolving even particles. The dimensions of solutes to be separated by these methods thus range from 10 -10 m to 10 -5 m. This situation may suggest that separation science and technology have been completely matured. However, studying new separation principles is still important, because they can allow the separation based on material properties that have not been utilized for conventional methods, provide higher performance and more efficient separation than existing means, and facilitate the understanding of materials through separation processes.According to chromatographic theories, the intrinsic separation performance of liquid chromatography is restricted in comparison with that of gas chromatography because of much lower solute diffusion in liquid phases. 11However, a liquid flow obviously provides versatile ways for material separation because liquids have higher density and dissolution power than gases, and thus has made possible application to various types of solutes with wide ranges in molecular weights and sizes. In the usual flow separation methods, appropriate chemical (chromatography) or physical (FFF) separation fields are created, which retain solutes to different extents and separate them. A variety of stationary phases for chromatography 2,[12][13][14] and physical forces for FFF [15][16][17][18][19] have been exploited, and have provided different capabilities and selectivity from those performed by conventional separation. In contrast, a separation method that requires neither chemical interactions nor special external fields should also be useful because of its instrumental simplicity. Hydrodynamic chromatography (HDC) is such a case, which allows separation of particles or macromolecules according to their hydrodynamic sizes just by passing them through a narrow channel. [20][21][22][23][24] Particles with larger diameter for example cannot approach the channel wall, and thus flow through the channel faster than the smaller particles, when the laminar flow profile is maintained therein. Although the applicability of this method was very restricted, recent developments of chip technology have brought about a remarkable progress. 23,24 If a capillary of radius a is used for HDC, the time for the elution of a particle of radius rp is given bywhere t0 is the time required ...

Analytical Conditions and Separation Performance of Capillary Chromatography Based on the Tube Radial Distribution of Aqueous-Organic Mixture Carrier Solvents under Laminar-Flow Conditions

“…Recently, capillary chromatography using open fused-silica capillary tubes that were not specially coated or modified were reported. [24][25][26][27][28] In one example, Tabata et al developed an open tubular capillary chromatography method based on the microphase separation of mixed solvents, even though they used narrow-bored tubes of 10 μm i.d. ; 27 when an acetonitrile-water mixture with a suitable salt concentration was pumped into a fused-silica capillary tube in which the inner wall was negatively charged due to the dissociation of its silanol groups, microphase separation occurred near the capillary wall, resulting in a water-enriched aqueous phase attached to the capillary inner wall.…”

Laminar dispersion at high Péclet numbers in finite-length channels: Effects of the near-wall velocity profile and connection with the generalized Leveque problem

“…The transition from the Taylor-Aris dispersion to new dispersion regimes has been described by several authors, 43,44,46 but no theoretical work thoroughly elucidated its properties. In point of fact, the scope of this article is precisely that of developing a comprehensive theory for dispersion in this regime.…”

“…The characterization of dispersion regimes in short columns at high Péclet numbers is also important in microfluidic analytical and separation devices related to the application of wide-bore chromatography, [42][43][44] which is used for characterization and separation of nanoparticles and micelles. The diction wide-bore chromatography refers to solute dispersion ͑chromatographic͒ experiments in mini-and microchannel in which the length ͑L͒ to radius ͑R͒ aspect ratio ␣ = L / R is not too high ͑␣ Յ 300͒.…”

“…Indeed, the occurrence of the transition from Taylor-Aris dispersion to convection-dominated regime, which has been qualitatively described by Vanderslice et al, 46 is the physical principle underlying the application of wide-bore chromatography as a hydrodynamic separation technique. 43,44 A complete scaling analysis for laminar parallel flows in channels of arbitrary cross section is developed, and it is shown that the scaling properties of the moment hierarchy depend strongly on the regularity of the crosssectional perimeter. If this perimeter is smooth ͑as in the case of circular capillaries͒ one observes that the variance of the outlet concentration profiles scales as Pe 1/3 ͑where Pe is the Péclet number, see Sec.…”

Wide-Bore Capillary Hydrodynamic Chromatography with ICP-MS Detection for Evaluation of Lanthanide Uptake by Molecular Aggregates

“…These aspects can be completely interpreted on the basis of the advection-diffusion equation, and its basic features have been experimentally revealed. [28][29][30] W-HDC is also efficient for evaluating the interaction between diffusive and non-diffusive analytes. If the system is ideally designed, the former gives a symmetric peak in the absence of the interaction, whereas its peak shape is deformed by the interaction with the latter.…”