Pressure dependence of diffusion coefficient and effect on plate height in liquid chromatography

Martin, Michel; Guiochon, Georges

doi:10.1021/ac00264a023

Cited by 27 publications

(5 citation statements)

References 47 publications

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“…These changes in diffusion coefficient need to be accounted for if a reduced parameter analysis is to yield meaningful results. This phenomenon was described in detail over 25 years ago by Martin and Guiochon but is generally ignored for the analysis of HPLC performed at lower pressure . To demonstrate the significance of this phenomenon under ultrahigh pressure conditions we have reanalyzed UHPLC data that was published a few years ago for a 49 cm long, 30 μm i.d.…”

Section: Resultsmentioning

confidence: 99%

Capillary-Based Instrument for the Simultaneous Measurement of Solution Viscosity and Solute Diffusion Coefficient at Pressures up to 2000 bar and Implications for Ultrahigh Pressure Liquid Chromatography

et al. 2009

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An instrument based on the Poiseuille flow principle capable of measuring solution viscosities at high pressures has been modified to observe UV-absorbent analytes in order to allow for the simultaneous measurement of analyte diffusivity. A capillary time-of-flight (CTOF) instrument was used to measure the viscosity of acetonitrile-water mixtures in all decade volume percent increments and the corresponding diffusion coefficients of small aromatic molecules in these solvent mixtures from atmospheric pressure to 2000 bar (approximately 30,000 psi) at 25 degrees C. The instrument works by utilizing a relatively small pressure drop (<100 bar) across a fused-silica capillary which has both the inlet and outlet pressurized so that the average column pressure can be significantly elevated (up to 2000 bar). Measurements with this instrument agree with high-pressure viscosity data collected previously using a CTOF viscometer, as well as with literature values obtained with falling-body viscometers of the Bridgman design. It has been further determined that, for the small molecules included in this study, trends in solute diffusivity with respect to pressure follow the predictions of the Stokes-Einstein equation when the solvent viscosity is corrected as a function of pressure. Because the instrument described herein determines viscosity and diffusivity independently, the effect of pressure on analyte hydrodynamic radius can also be monitored. An analysis of ultrahigh pressure liquid chromatography (UHPLC) data was performed using the pressure-corrected diffusion coefficient of hydroquinone to demonstrate the effect of this phenomenon on the analysis of chromatographic performance.

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Section: Resultsmentioning

confidence: 99%

Capillary-Based Instrument for the Simultaneous Measurement of Solution Viscosity and Solute Diffusion Coefficient at Pressures up to 2000 bar and Implications for Ultrahigh Pressure Liquid Chromatography

et al. 2009

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“…Piel [25], Locke [26], and Guiochon [27 -33] have reported that the influence of pressure in the HPLC system on column efficiency is usually small. The variation in diffusion coefficient can be estimated as 1% per 1 MPa pressure increase [30,32], along with minor effects on retention times [28]. The effect seems to be too small to account for the larger decrease in column efficiency observed for Chromolith columns on connection of the fifth or sixth, as shown in Table 4.…”

Section: True Performance Of Monolithic Silica Capillary Columnsmentioning

confidence: 96%

How to utilize the true performance of monolithic silica columns

Ikegami¹,

Dicks

Kobayashi

et al. 2004

J of Separation Science

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Ways of utilizing the true separation efficiency of monolithic silica (MS) columns were studied. The true performance of MS columns, both regular-sized (rod-type clad with PEEK resin, 4.6 mm ID, 10 cm) and capillary sized (in 100 or 200 microm ID fused silica capillary, 25-140 cm) was evaluated by calculating the contribution of extra-column effects. HETP values of 7-9 microm were observed for solutes having retention factors (kvalues) of up to 4 for rod columns and up to 15 for a capillary column. The high permeability of MS columns allowed the use of long columns, with several connected together in the case of rod columns. Narrow-bore connectors gave good results. Peak variance caused by a column connector ranges from 50 to 70% of that caused by one rod-type column for up to three connectors or four columns in 80% methanol, but the addition of a 4th or 5th connector to add a 5th and 6th column, respectively, caused a much greater increase in peak variance, especially for long-retained solutes, which is greater than the variance caused by one rod column. Rod columns seem to show slightly lower efficiency at a pressure higher than 10 MPa or so. The use of acetonitrile-water as a mobile phase better preserved the ability of individual rod columns to generate up to 100,000 theoretical plates with 14 columns connected. Methods for eliminating extra-column effects in micro-HPLC were also studied. Split injection and on-column detection resulted in optimum performance. A long MS capillary measuring 140 cm produced 160,000 theoretical plates. The column efficiency of a capillary column was not affected by the pressure, showing advantages over the rod columns that exhibited peak broadening caused by connectors and pressure.

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“…An uneven radial temperature profile produces solute retention alteration and additional band broadening [63,79]. Reducing the column diameter to capillary dimensions largely eliminates this effect as illustrated in Table 3 [63].…”

Section: Frictional Heatingmentioning

confidence: 99%

Fast analysis in liquid chromatography using small particle size and high pressure

Nguyen

Guillarme

Rudaz

et al. 2006

J of Separation Science

303

164

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ReviewFast analysis in liquid chromatography using small particle size and high pressureIn order to enhance chromatographic performances in terms of efficiency and rapidity, LC has recently evolved in the development of short columns packed with small particles (sub-2 lm) working at high pressures (A400 bar). This approach has been described 30 years ago according to the fundamental chromatographic equations. However, systems and columns compatible with such high pressures have been introduced in the market in 2004 only. Advantages of small particles working at high pressure will be discussed in terms of sensitivity, efficiency, resolution, and analysis time. Potential problems encountered with high pressure in terms of frictional heating and solvent compressibility will also be discussed even if systems working at a maximum pressure of 1000 bar are not influenced by these parameters and give reliable and reproducible results. Several applications will highlight the potential and interest of this new technology.

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Pressure dependence of diffusion coefficient and effect on plate height in liquid chromatography

Cited by 27 publications

References 47 publications

Capillary-Based Instrument for the Simultaneous Measurement of Solution Viscosity and Solute Diffusion Coefficient at Pressures up to 2000 bar and Implications for Ultrahigh Pressure Liquid Chromatography

Capillary-Based Instrument for the Simultaneous Measurement of Solution Viscosity and Solute Diffusion Coefficient at Pressures up to 2000 bar and Implications for Ultrahigh Pressure Liquid Chromatography

How to utilize the true performance of monolithic silica columns

Fast analysis in liquid chromatography using small particle size and high pressure

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