Search results for: Georges Guiochon

Items from 1 to 20 out of 452 results

article

On the catastrophic explosion of the AZF plant in Toulouse

Georges Guiochon

Process Safety Progress > 39 > 4 > n/a - n/a

On September 21, 2001, around 10:17 am, a warehouse containing about 300 metric tons of ammonium nitrate rejects exploded in the AZF/Grande Paroisse plant in Toulouse (France), causing 31 deaths, hundreds of casualties, and enormous damages. The criminal investigation focused exclusively on the explosion itself and neglected the long chain of precursor events that took place in the previous hours,...

article

Hydrophilic interaction chromatography: A promising alternative to reversed‐phase liquid chromatography systems for the purification of small protonated bases

Fabrice Gritti, Georges Guiochon

Journal of Separation Science > 38 > 10 > 1633 - 1641

The overloaded band profiles of the protonated species of propranolol and amitriptyline were recorded under acidic conditions on four classes of stationary phases including a conventional silica/organic hybrid material in reversed‐phase liquid chromatography mode (BEH‐C₁₈), an electrostatic repulsion reversed‐phase liquid chromatography C₁₈ column (BEH‐C₁₈+), a poly(styrene‐divinylbenzene) monolithic...

article

The quantitative impact of the mesopore size on the mass transfer mechanism of the new 1.9μm fully porous Titan-C18 particles II – Analysis of biomolecules

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2015 > 1392 > Complete > 10-19

The kinetic performances of 3.0×100mm columns packed with 1.9μm Titan-C ₁₈ particles with average mesopore sizes of 80Å and 120Å were investigated quantitatively for the analysis of biomolecules. Large mesopores are expected to speed up the rate of diffusivity of high-molecular-weight compounds across the stationary phase and to generate higher plate counts at high velocities. The mass transfer...

article

The quantitative impact of the mesopore size on the mass transfer mechanism of the new 1.9μm fully porous Titan-C18 particles. I: Analysis of small molecules

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2015 > 1384 > Complete > 76-87

Previous data have shown that could deliver a minimum reduced plate height as small as 1.7. Additionally, the reduction of the mesopore size after C ₁₈ derivatization and the subsequent restriction for sample diffusivity across the Titan-C ₁₈ particles were found responsible for the unusually small value of the experimental optimum reduced velocity (5 versus 10 for conventional particles)...

article

The relative importance of the adsorption and partitioning mechanisms in hydrophilic interaction liquid chromatography

Fabrice Gritti, Alexandra Höltzel, Ulrich Tallarek, Georges Guiochon

Journal of Chromatography A > 2015 > 1376 > Complete > 112-125

We propose an original model of effective diffusion along packed beds of mesoporous particles for HILIC developed by combining Torquatos model for heterogeneous beds (external eluent+particles), Landauers model for porous particles (solid skeleton+internal eluent), and the time-averaged model for the internal eluent (bulk phase+diffuse water (W) layer+rigid W layer). The new model allows to determine...

article

Separation of peptides and intact proteins by electrostatic repulsion reversed phase liquid chromatography

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1374 > Complete > 112-121

A new brand of BEH-C₁₈ hybrid particles chemically bonded to a leash carrying an amine group permits the implementation of electrostatic repulsive interactions chromatography. Using columns packed with this material, the influence of the concentration of positive charges bonded to the BEH-C₁₈ surface on the overloaded band profiles of a few positively charged peptides and proteins was investigated...

article

Effects of the surface concentration of fixed charges in C18-bonded stationary phases on the adsorption process and on the preparative chromatography of small ionizable compounds

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1372 > Complete > 42-54

The effects of the surface concentration of positive charges attached to the surface of research BEH-C ₁₈ hybrid particles on the overloaded band profiles and the adsorption isotherms of a neutral (caffeine) and a positively charged (nortryptilinium hydrochloride) compounds were measured and investigated. The inverse method (IM) of chromatography was used to determine the isotherm parameters...

article

Characterization and kinetic performance of 2.1 × 100 mm production columns packed with new 1.6 μm superficially porous particles

Fabrice Gritti, Stephen Shiner, Jacob N. Fairchild, Georges Guiochon

Journal of Separation Science > 37 > 23 > 3418 - 3425

The overall kinetic performance of three production columns (2.1 mm × 100 mm format) packed with 1.6 μm superficially porous CORTECS‐C₁₈+ particles was assessed on a low‐dispersive I‐class ACQUITY instrument. The values of their minimum intrinsic reduced plate heights (h_min = 1.42, 1.57, and 1.75) were measured at room temperature (295 K) for a small molecule (naphthalene) with an acetonitrile/water...

article

Estimations of temperature deviations in chromatographic columns using isenthalpic plots. I. Theory for isocratic systems

Abhijit Tarafder, Pamela Iraneta, Georges Guiochon, Krzysztof Kaczmarski, more

Journal of Chromatography A > 2014 > 1366 > Complete > 126-135

We propose to use constant enthalpy or isenthalpic diagrams as a tool to estimate the extent of the temperature variations caused by the mobile phase pressure drop along a chromatographic column, e.g. of its cooling in supercritical fluid and its heating in ultra-performance liquid chromatography. Temperature strongly affects chromatographic phenomena. Any of its variations inside the column, whether...

article

Mass transport of small retained molecules in polymer-based monolithic columns

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1362 > C > 49-61

The mass transport properties of a non-retained (thiourea) and three retained low molecular weight compounds (acetophenone, valerophenone, and octanophenone) along a 4.6mm×45mm PROSWIFT™ RP-1S monolithic column made of rigid cross-linked poly(styrene-divinylbenzene) copolymer was investigated in depth. Accurate protocols (peak parking experiments, measurement of the first and second central moments...

article

Calculated and experimental chromatograms for distorted gradients and non-linear solvation strength retention models

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1356 > Complete > 96-104

Computer calculations of gradient chromatograms were performed by taking into account the adsorption behavior of the strong eluent in RPLC and the true Henry constant of the analytes. This improves the accuracy of classical gradient calculations, which all assume no affinity of the eluent modifier for the stationary phase and that the linear solvation strength model (LSSM) applies. The excess adsorption...

article

Particle size distribution and column efficiency. An ongoing debate revived with 1.9μm Titan-C18 particles

Fabrice Gritti, David S. Bell, Georges Guiochon

Journal of Chromatography A > 2014 > 1355 > Complete > 179-192

The mass transfer mechanism in four prototype columns (2.1 and 3.0×50mm, 2.1 and 3.0×100mm) packed with 1.9μm fully porous Titan-C ₁₈ particles was investigated by using two previously reported home-made protocols. The first one was used to measure the eddy dispersion HETP of these new columns, the second one to estimate their intrinsic (corrected for HPLC system contribution) HETPs. Titan...

article

The rationale for the optimum efficiency of columns packed with new 1.9μm fully porous Titan-C18 particles—A detailed investigation of the intra-particle diffusivity

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1355 > Complete > 164-178

In a previous report, it was reported that columns packed with fully porous 1.9μm Titan-C ₁₈ particles provided a minimum reduced plate height as small as 1.7 for the most retained compound (n-octanophenone) under RPLC conditions. These particles are characterized by a relatively narrow size distribution with a relative standard deviation (RSD) of only 10%. A column packed with classical 5μm...

article

Effect of the pressure on pre-column sample dispersion theory, experiments, and practical consequences

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1352 > Complete > 20-28

The effect of the pressure on the dispersion of a low molecular weight compound along 0.508 and 1.016mm i.d. × 50cm long open circular tubes was investigated theoretically and experimentally. The theoretical predictions were based on the early models of dispersion derived by Aris and Taylor (1953) and on the approximate model of Alizadeh for the time moments (1980). Experimentally, the system pressure...

article

Possible resolution gain in enantioseparations afforded by core–shell particle technology

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1348 > Complete > 87-96

Whether columns packed with core–shell particles may outperform those packed with fully porous particles for chiral separations is controversial. The potential advantages of such columns are investigated from a theoretical viewpoint. The height equivalent to a theoretical plate (HETP) associated to the slow adsorption-desorption process typical of chiral chromatography was derived from the Laplace...

article

The adsorption of naproxen enantiomers on the chiral stationary phase (R,R)-whelk-O1 under supercritical fluid conditions

Fahimeh Kamarei, Péter Vajda, Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1345 > Complete > 200-206

The adsorption isotherms of the Naproxen enantiomers eluted with a mixture of carbon dioxide and methanol on a (R,R)-Whelk-O1 column were measured using frontal analysis and the inverse method. Sharp breakthrough fronts provided using a modified design of the instrument allowed an accurate determination of these isotherms. The adsorption model that best accounts for the data was derived from the analysis...

article

Separations by gradient elution: Why are steep gradient profiles distorted and what is their impact on resolution in reversed-phase liquid chromatography

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1344 > Complete > 66-75

The formation of a concentration shock layer of either methanol or acetonitrile used as the modifier in steep RPLC aqueous/organic gradients was predictable from their excess adsorption isotherm and was directly observed from their elution profiles recorded in UV absorption. A discontinuity of the concentration profile of the organic modifier arises and grows along the column. Its effects on the peak...

article

Volume based vs. time based chromatograms: Reproducibility of data for gradient separations under high and low pressure conditions

Joseph J. Stankovich, Fabrice Gritti, Paul G. Stevenson, Péter Vajda, more

Journal of Chromatography A > 2014 > 1343 > Complete > 79-90

A critical aspect in fast gradient separations carried out under constant pressure, in the very high pressure liquid chromatography (VHPLC) mode is that time-based chromatograms may not yield highly reproducible separations. A proposed solution to improve the reproducibility of these separations involves plotting the chromatograms as functions of the volume eluted vs. UV absorbance instead of time...

article

Band broadening along gradient reversed phase columns: A potential gain in resolution factor

Fabrice Gritti, Georges Guiochon

Journal of Chromatography A > 2014 > 1342 > Complete > 24-29

The advantages of using columns packed with stationary phases having a composition gradient so that retention factors increase toward the outlet and eluting them with an isocratic mobile phase may provide increased peak resolution in liquid chromatography. This approach is discussed from a theoretical viewpoint. The retention factor is assumed to increase linearly along the column. The peak width...

article

Comparison of volume and concentration overloadings in preparative enantio-separations by supercritical fluid chromatography

Péter Vajda, Fahimeh Kamarei, Attila Felinger, Georges Guiochon

Journal of Chromatography A > 2014 > 1341 > Complete > 57-64

The adsorption isotherms of both naproxen enantiomers were measured on a (R,R)-Whelk-O1 chiral adsorbent from a mobile phase made of liquid carbon dioxide and methanol, using frontal analysis. These isotherms were used to model the competitive adsorption behavior of a racemic mixture of naproxen enantiomers. Their overloaded elution band profiles were calculated numerically using these isotherm data...

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COLUMN EFFICIENCY (49)
FRONTAL ANALYSIS (43)
ADSORPTION ISOTHERMS (27)
PHENOL (25)
PREPARATIVE CHROMATOGRAPHY (24)
SUPERCRITICAL FLUID CHROMATOGRAPHY (22)
HETP (20)
BAND PROFILES (19)
MASS TRANSFER MECHANISM (19)
RPLC (19)
GRADIENT ELUTION (18)
LIQUID CHROMATOGRAPHY (18)
ADSORPTION ISOTHERM (17)
EDDY DIFFUSION (17)
CAFFEINE (16)
SHELL PARTICLES (15)
PEAK CAPACITY (14)
CORE–SHELL PARTICLES (13)
EDDY DISPERSION (13)
MASS TRANSFER KINETICS (13)
STATIONARY PHASES, LC (13)
ACETONITRILE (12)
COLUMN TECHNOLOGY (12)
ADSORPTION EQUILIBRIUM (11)
INSULIN (11)
LONGITUDINAL DIFFUSION (11)
MASS TRANSFER (11)
OVERLOADED BAND PROFILES (11)
ADSORPTION ENERGY DISTRIBUTION (10)
AFFINITY ENERGY DISTRIBUTION (10)
COLUMN HETEROGENEITY (10)
HALO-C18 (10)
RETENTION MECHANISM (10)
SFC (10)
ISOTHERM MODELING (9)
KINETEX-C18 (9)
NAPHTHALENE (9)
PROPRANOLOL (9)
RP-HPLC (9)
SOLID–LIQUID MASS TRANSFER RESISTANCE (9)
COLUMN PACKING TECHNOLOGY (8)
ENANTIOMER SEPARATION (8)
MONOLITHIC COLUMNS (8)
OPTIMIZATION (8)
FILM MASS TRANSFER (7)
NAPROXEN (7)
NONLINEAR CHROMATOGRAPHY (7)
OPERATING CONDITIONS (7)
PEAK PROFILES (7)
PRESSURE DROP (7)
SILICA (7)
TOLUENE (7)
ADSORPTION (6)
COLUMN PERFORMANCE (6)
EQUILIBRIUM-DISPERSIVE MODEL (6)
HEAT GENERATION (6)
HEAT TRANSFER (6)
HPLC (6)
IONIC STRENGTH (6)
MOBILE PHASE COMPOSITION (6)
NAPHTHO[2,3-A]PYRENE (6)
PRESSURE (6)
QUINIDINE CARBAMATE (6)
AXIAL DIFFUSION (5)
CHIRAL STATIONARY PHASE (5)
CHROMATOGRAPHY (5)
ETHYLBENZENE (5)
EXTRA-COLUMN BAND BROADENING (5)
FMOC-L-TRYPTOPHAN IMPRINTED POLYMERS (5)
HEAT EFFECTS (5)
HILIC (5)
INVERSE METHOD (5)
METHANOL (5)
MOMENT ANALYSIS (5)
PEAK TAILING (5)
REPRODUCIBILITY (5)
SURFACE HETEROGENEITY (5)
THIOUREA (5)
TRANS-COLUMN EFFECT (5)
VISCOUS FRICTION (5)
1-INDANOL (4)
2D-HPLC (4)
ADSORPTION MECHANISM (4)
ANILINE (4)
AXIAL TEMPERATURE PROFILES (4)
BAND BROADENING (4)
BEH-C18 (4)
C18-BONDED SILICA (4)
CELLULOSE TRIBENZOATE (4)
CHIRALPAK AD (4)
COLUMN-TO-COLUMN REPEATABILITY (4)
DENSITY DROP (4)
ENDCAPPING (4)
ETHANESULFONIC ACID (4)
EXTRA-COLUMN EFFECTS (4)
FAST CHROMATOGRAPHY (4)
HEAT BALANCE (4)
HETP EQUATION (4)
INTRA-PARTICLE DIFFUSIVITY (4)
INTRAPARTICLE DIFFUSION (4)
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Journal of Chromatography A (370)
Analytical Chemistry (37)
Chemical Engineering Science (18)
Journal of Separation Science (4)
The Journal of Physical Chemistry B (4)
AIChE Journal (3)
Journal of Colloid And Interface Science (3)
Langmuir (3)
Analytical Biochemistry (1)
Computers and Geotechnics (1)
Industrial & Engineering Chemistry Research (1)
Journal of Chemometrics (1)
Magnetic Resonance Imaging (1)
Process Safety Progress (1)
Talanta (1)
Thermochimica Acta (1)
TrAC - Trends in Analytical Chemistry (1)
Trends in Analytical Chemistry (1)
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INFONA - science communication portal

Search results for: Georges Guiochon

On the catastrophic explosion of the AZF plant in Toulouse

Hydrophilic interaction chromatography: A promising alternative to reversed‐phase liquid chromatography systems for the purification of small protonated bases

The quantitative impact of the mesopore size on the mass transfer mechanism of the new 1.9μm fully porous Titan-C18 particles II – Analysis of biomolecules

The quantitative impact of the mesopore size on the mass transfer mechanism of the new 1.9μm fully porous Titan-C18 particles. I: Analysis of small molecules

The relative importance of the adsorption and partitioning mechanisms in hydrophilic interaction liquid chromatography

Separation of peptides and intact proteins by electrostatic repulsion reversed phase liquid chromatography

Effects of the surface concentration of fixed charges in C18-bonded stationary phases on the adsorption process and on the preparative chromatography of small ionizable compounds

Characterization and kinetic performance of 2.1 × 100 mm production columns packed with new 1.6 μm superficially porous particles

Estimations of temperature deviations in chromatographic columns using isenthalpic plots. I. Theory for isocratic systems

Mass transport of small retained molecules in polymer-based monolithic columns

Calculated and experimental chromatograms for distorted gradients and non-linear solvation strength retention models

Particle size distribution and column efficiency. An ongoing debate revived with 1.9μm Titan-C18 particles

The rationale for the optimum efficiency of columns packed with new 1.9μm fully porous Titan-C18 particles—A detailed investigation of the intra-particle diffusivity

Effect of the pressure on pre-column sample dispersion theory, experiments, and practical consequences

Possible resolution gain in enantioseparations afforded by core–shell particle technology

The adsorption of naproxen enantiomers on the chiral stationary phase (R,R)-whelk-O1 under supercritical fluid conditions

Separations by gradient elution: Why are steep gradient profiles distorted and what is their impact on resolution in reversed-phase liquid chromatography

Volume based vs. time based chromatograms: Reproducibility of data for gradient separations under high and low pressure conditions

Band broadening along gradient reversed phase columns: A potential gain in resolution factor

Comparison of volume and concentration overloadings in preparative enantio-separations by supercritical fluid chromatography

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