Radial heterogeneity of some analytical columns used in high-performance liquid chromatography

Abia, Jude A.; Mriziq, Khaled S.; Guiochon, Georges

doi:10.1016/j.chroma.2009.02.034

Cited by 85 publications

(40 citation statements)

References 23 publications

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“…The external porosities of the Luna(2)-C 18 and Jupiter-C 18 columns (e e ¼ 0.361 and 0.387 AE 0.001, respectively) were determined from the results of the total pore-blocking experiments, 36 using sodium nitrate as the unretained compound. the first two moments of the concentration distribution represented by the solid black line; the upper integration limit is chosen once 99.5% of the injected mass is eluted as represented by the solid red line or the cumulative eluted mass; (B) determination of the h data from the measurement of the elution time at the peak apex (t R ) and the bandwidth at half the height of the peak (t r,1/2 2 t f,1/2 ).…”

Section: Methodsmentioning

confidence: 99%

“…The overall eddy dispersion term of a retained solute was two to three times larger when it had no access to the mesopore volume than when it had access to them. Trans-column eddies were always suspected as be a source of band broadening in packed columns, as already observed in packed columns [15][16][17][18] and more recently in monolithic columns. [19][20][21] Still, this observation does not explain why the A-term is significantly higher when access to the mesopore volume is blocked.…”

Section: Introductionmentioning

confidence: 96%

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Impact of retention on trans‐column velocity biases in packed columns

Gritti

Guiochon

2009

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).The heights equivalent to a theoretical plate of a weakly and strongly retained compounds were measured on two packed columns having different average mesopore sizes. The measurements were carried out in two different cases, with access to the mesopores by the sample molecules blocked (filled with n-nonane) or not. The experimental results demonstrate that the eddy dispersion terms of both columns are significantly smaller for porous than for nonporous particles. Two simultaneous phenomena explain this observation. First, packed columns are radially heterogeneous which causes significant trans-column velocity biases warping the bands. Second, radial dispersion contributes to mass transfer across the column, relaxing the radial concentration gradients that are caused by these velocity biases. The impact of these biases is minimized when the pores of the particles are not blocked; it decreases with increasing residence time and radial dispersion coefficient of the solutes. V

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Impact of retention on trans‐column velocity biases in packed columns

Gritti

Guiochon

2009

AIChE Journal

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“…Studies have shown that the eddy dispersion in columns increases as the particle size becomes smaller indicating that efficiency is limited by non uniform packing [149]. This arises from a radial distribution of packing densities in the cylindrical tube, giving a radial distribution of velocities that broadens peaks [150][151][152][153]. Recent experiments bear this out: nonporous 1.0 μm particles in capillaries of varying diameter show that the A term is primarily due to the radial heterogeneity of the packing.…”

Section: Future Perspectives For Column Technologymentioning

confidence: 91%

Evolution and Current Trends in Liquid and Supercritical Fluid Chromatography

Fekete¹,

Perrenoud²,

Guillarme

2014

CCHG

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Abstract:The current trend in high performance liquid chromatography (HPLC) tends toward the achievement of higher separation efficiency and shorter analysis time. Indeed, better performance in LC has become increasingly important in recent years mainly driven by the challenges of either analyzing more complex samples or increasing the numbers of samples per time unit. In the recent development of particle technology, the use of fully porous sub-2 m particles and sub-3 m shell particles have received considerable attention. Beside packed columns, the new generation of silica-based monolithic columns also offers very high separation power. However, to take full advantage of these innovative phases, the chromatographic system has also to be drastically optimized in terms of upper pressure limit and system volume.This revolution in column technology now spreads and covers several modes of liquid chromatography such as reversedphase liquid chromatography (RPLC), hydrophilic interaction liquid chromatography (HILIC), or even supercritical fluid chromatography (SFC). The HILIC and SFC, which can be considered as alternative modes of chromatography, could also be useful to extend the applicability of chromatography towards the analysis of very hydrophilic and lipophilic compounds, respectively.The present review gives an insight about the theory behind the success of current column technology and presents a summary of latest applications, using various modes of one-dimensional chromatography (RPLC, HILIC, SFC). This paper also shows that theoretically expected column efficiency could sometimes be compromised in practical work especially in the case of narrow bore columns.

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“…columns, the relative difference between the eluent velocities at the column center and near its wall is of the order of a few percent. 6 The corresponding reduced eddy dispersion term varies proportionally to the column length. It was recently reported that the porosity of the particles, hence the surface area available for analyte adsorption and retention, have a significant impact on the trans-column eddy dispersion term.…”

Section: Introductionmentioning

confidence: 99%

Importance of sample intraparticle diffusivity in investigations of the mass transfer mechanism in liquid chromatography

Gritti

Guiochon

2011

AIChE Journal

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The effective diffusivity of a nonretained (thiourea) and of a strongly retained (phenol) compounds were measured with the peak parking method in two different columns (both 150 Â 4.6 mm) packed with two types of porous particles having different mesopore sizes [5 lm Jupiter-C 18 , 320 A and Luna(2)-C 18 , 100 A ]. The eluent was a methanol-water mixture (10/90 v/v) and the temperature 294 K. The effective diffusivity data acquired were used to determine the intraparticle diffusivity, D p , based on two different diffusion models. The first one assumes that the diffusion fluxes across the particles and in the interparticle volume are additive (parallel diffusion model). The second model was rigorously derived on the basis of the effective medium theory of diffusion (diffusion model) in a binary composite medium (particles þ interparticle volume). In both models, it was assumed that the rate of equilibrium between the liquid and the solid phases was infinitely faster than the rate of axial diffusion along the column at zero flow rate. Both models provide physically meaningful intraparticle diffusivity coefficients that take into account the average mesopore size of the particles, their specific surface area, and the retention factor of the analyte. Although the actual effective intraparticle diffusivity remains unknown, these result confirm that the mass transfer resistance due to diffusion through the porous particles has almost negligible effects in reversed phase liquid chromatography due to the importance of surface diffusion. Combining the results of the peak parking method with the h data measured at high linear velocities allows the unambiguous measurement of the film mass transfer and the surface diffusion coefficients.

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Radial heterogeneity of some analytical columns used in high-performance liquid chromatography

Cited by 85 publications

References 23 publications

Impact of retention on trans‐column velocity biases in packed columns

Impact of retention on trans‐column velocity biases in packed columns

Evolution and Current Trends in Liquid and Supercritical Fluid Chromatography

Importance of sample intraparticle diffusivity in investigations of the mass transfer mechanism in liquid chromatography

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