Is chromatography a mass transfer process?

Mass transfer in gas chromatography takes place through diffusion across the gas stream, to the porous particles of support or adsorbent, then through diffusion in the stagnant gas which impregnates these particles and finally through diffusion in the liquid phase or adsorption-desorption on the gas-solid interface.

How does mass affect chromatography?

Larger molecules take longer to move up the chromatography paper or TLC plate, whereas smaller molecules are more mobile. Likewise, the polarity of the molecules can affect how far the spots travel, depending on the type of solvent used.

What is mass transfer effects?

Mass transfer is the net movement of mass from one location, usually meaning stream, phase, fraction or component, to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, and distillation.

What is resistance to mass transfer in chromatography?

Overall resistance to mass transfer inside a chromatographic column is the combined result of longitudinal diffusion along the column, eddy dispersion, external film mass transfer resistance, mass transfer resistance inside the pores of the stationary phase, rate of adsorption and desorption as well as the friction- …

What is mobile phase mass transfer?

Mobile phase mass transfer – a process of peak broadening caused by the presence of different flow profile within channels or between particles of the support in the column.

What is longitudinal diffusion in chromatography?

Answer and Explanation: The diffusion of the analyte from the concentrated middle region of the band with the dilute region obtained in the chromatogram shows the broadened bands on both sides of a head band-center. This kind of diffusion is termed as longitudinal diffusion.

How does mass affect paper chromatography?

Does molar mass affect column chromatography?

It is highly dependent to the nature of your beads. Column dimensions such as length and inner diameter affect only physical aspect of your separation (speed and efficiency). Thus, as Masood Sepehrimanesh stated, there is no direct relation to molecular weight of analytes.

What causes mass transfer?

Mass transfer is an important phenomenon with numerous applications in food processing. Concentration gradients of a substance in a food cause diffusion of that substance from high to low concentration. Convection mass transfer is caused by convective currents within liquids and gases. …

What is mass transfer in fermentation?

This type of fermenter is essentially a mass transfer device that promotes the transfer of oxygen from gas bubbles into the liquid medium where the microbes live. Often the rate of oxygen transfer is the limiting factor in the whole manufacturing process.

What is meant by eluent?

Eluent. The eluent or eluant is the “carrier” portion of the mobile phase. In liquid chromatography, the eluent is the liquid solvent; in gas chromatography, it is the carrier gas.

What is rate theory?

Rate theory is a concept in chemistry that describes the process of peak dispersion, and it provides an equation to calculate the variance per unit length of the column. This theory is very useful in column chromatography. Rate theory provides a more realistic description of the processes that work inside a column.

What are the different types of chromatographic methods?

Classification of chromatographic methods: 1. physical means column chromatography: stationary phase is held in a narrow capillary through which the mobile phase is forced under pressure or by gravity; planar chromatography: stationary phase is supported on a flat plate or in the interstices of a paper.

What is the capacity factor in chromatography?

The Capacity Factor • For each peak in the chromatogram, the capacity factor, k’, is defined as: m R m t t t k − ‘= time solute spends in mobile phase time solute spends in stationary phase k’=

What causes band spreading in column chromatography?

A band of solute broadens as it moves through a column. Ideally, an infinitely narrow band applied to the inlet of the column emerges with a Gaussian shape at the outlet. Diffusion (cont.) One main cause of band spreading is diffusion.

What is the retention time in chromatography?

Thus its retention time t M is approximately equal to the time required for a molecule of the mobile phase to pass through the column. A typical chromatogram for a two-component mixture Retention time, t R t R is the time it takes after a sample injection for the analyte peak to reach the detector.