Theory and Application of the Two-Mode Gradient Elution in Liquid Chromatography Involving Simultaneous Changes in Temperature and Mobile-Phase Composition

Nikitas, P.; Pappa-Louisi, A.; Papachristos, Kostas; Zisi, Ch.

doi:10.1021/ac800514m

Cited by 25 publications

(18 citation statements)

References 31 publications

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“…However, it is not a simple task to find a proper optimization algorithm handling more variables. Usually, these approaches are focused on the description of the retention variation with composition in ternary mobile phase or with composition in binary mobile phases simultaneously with mobile phase pH and/or column temperature . There is also a paper describing the simultaneous effect of eluent pH and column temperature on the retention of ionizable solutes .…”

Section: Characterization Of Hplc and Sfc Separation Systemsmentioning

confidence: 99%

Chromatographic methods enabling the characterization of stationary phases and retention prediction in high‐performance liquid chromatography and supercritical fluid chromatography

Sýkora

Vozka

Tesařová

2015

J of Separation Science

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In the scope of the present review, the current status of high-performance liquid chromatography/ultra-high performance liquid chromatography and supercritical fluid chromatography is briefly provided. These techniques and their retention mechanisms are compared. Various alternative approaches utilized for the determination and description of the retention processes in these two systems are mapped. Two frequently used concepts, linear-free energy relationships, and hydrophobic subtraction models, used for the characterization of the retention interactions, are discussed. Principles and selected applications of the both methods are also covered. Then the models applied for the prediction of retention behavior of solutes on stationary phases are outlined. The procedures utilized for the sorbent/column classification are also covered. Simple chromatographic tests frequently used for the basic characterization and mutual comparison of stationary phases are summarized and briefly commented on. The importance of a statistical evaluation of complex retention data obtained from the chromatographic measurements is outlined. Finally, computer simulations aiming at the facilitation of the quest to optimize separation conditions for a given mixture of analytes are touched upon.

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Section: Characterization Of Hplc and Sfc Separation Systemsmentioning

confidence: 99%

Chromatographic methods enabling the characterization of stationary phases and retention prediction in high‐performance liquid chromatography and supercritical fluid chromatography

Sýkora

Vozka

Tesařová

2015

J of Separation Science

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“…The interested reader is again referred to the respective literature dealing with different models for retention time predictions when temperature is used as the active variable in high-temperature liquid chromatography. 111,125,128 Also, some academic tools, which have been developed by the groups of Nikitas and Pappa-Louisi 127,128 as well as Cela (PREGA), are very helpful when simultaneous gradients of the organic solvent and temperature are employed. In the following sections, some examples that illustrate the effect of temperature either in isothermal or temperature gradient mode are given.…”

Section: Van't Hoff Equationmentioning

confidence: 99%

High-Temperature Liquid Chromatography

Teutenberg

2015

Fast Liquid Chromatography–Mass Spectrometry Methods in Food and Environmental Analysis

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In recent years, the use of elevated temperatures in liquid chromatography has become more familiar, although many people still fear to increase the temperature because of unwanted side effects. In most laboratories, separations are usually performed at room temperature. In this setting, elevated-temperature liquid chromatography would mean the temperature ranges from 40 °C to 60 °C, whereas high-temperature liquid chromatography extends from 60 °C to 200 °C. The lower temperature limit of 60 °C is defined by the fact that some solvents that are used in liquid chromatography start to boil above that temperature, 1 while the upper temperature limit is dictated by the column stability. Most stationary phases are not stable if the temperature is increased above 150 °C, although it would be very easy to heat a column to a much higher temperature. In fact, only a few stationary phases can be used with an acceptable lifetime between 150 °C and 200 °C. 2 In the literature, many different terms have been used. These are:• Subcritical water chromatography 3-16 • Elevated-temperature liquid chromatography 17-39 • Superheated water chromatography 40-59 • Hot eluent liquid chromatography 60 Fast Liquid Chromatography-Mass Spectrometry Methods in Food and Environmental Analysis Downloaded from www.worldscientific.com by CHINESE UNIVERSITY OF HONG KONG on 02/08/15. For personal use only.

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“…Meanwhile, the dk/d derivative in Eq. (19), and consequently, dl/dt, depend on the retention model. Both the linear (Eq.…”

Section: Integration Of the General Equation For Gradient Elutionmentioning

confidence: 99%

“…Nikitas and Pappa‐Louisi discussed the different approaches, and proposed the direct integration of Eq. using a numerical approach , which has been also applied by other authors . At constant flow rate:

\frac{L}{u} = t_{0} = \int_{0}^{t_{g}} \frac{d t}{1 + k (φ (t, l))}

where L is the total column length.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Some insights on the description of gradient elution in reversed‐phase liquid chromatography

Baeza-Baeza

García-Álvarez-Coque

2014

J of Separation Science

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The so-called "fundamental equation for gradient elution" has been used for modeling the retention in gradient elution. In this approach, the instantaneous retention factor (k) is expressed as a function of the change in the modifier content (φ(ts )), ts being the time the solute has spent in the stationary phase. This approach can only be applied at constant flow rate and with gradients where the elution strength depends on the column length following a f(t-l/u) function, u being the linear mobile phase flow rate, and l the distance from the column inlet to the location where the solute is at time t measured from the beginning of the gradient. These limitations can be solved by using the here called "general equation for gradient elution", where k is expressed as a function of φ(t,l). However, this approach is more complex. In this work, a method that facilitates the integration of the "general equation" is described, which allows an approximate analytical solution with the quadratic retention model, improving the predictions offered by the "linear solvent strength model." It also offers direct information about the changes in the instantaneous modifier content and retention factor, and gives a meaning to the gradient retention factor.

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Theory and Application of the Two-Mode Gradient Elution in Liquid Chromatography Involving Simultaneous Changes in Temperature and Mobile-Phase Composition

Cited by 25 publications

References 31 publications

Chromatographic methods enabling the characterization of stationary phases and retention prediction in high‐performance liquid chromatography and supercritical fluid chromatography

Chromatographic methods enabling the characterization of stationary phases and retention prediction in high‐performance liquid chromatography and supercritical fluid chromatography

High-Temperature Liquid Chromatography

Some insights on the description of gradient elution in reversed‐phase liquid chromatography

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