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Questions and Answers
What contributes to zone broadening in chromatography?
What contributes to zone broadening in chromatography?
- Temperature variation, pressure changes, column length
- Sample concentration, solvent polarity, column material
- Flow rate variation, solute size, stationary phase viscosity
- Longitudinal diffusion, resistance to mass transfer, multiple path effect (correct)
What does the band broadening due to longitudinal diffusion depend on?
What does the band broadening due to longitudinal diffusion depend on?
- Temperature and pressure of the mobile phase
- Solute size and solvent polarity
- Column length and sample concentration
- Diffusion of the solute and the flow rate of the solute through the column (correct)
What does the formula $HL = \frac{L}{V} DM$ represent in chromatography?
What does the formula $HL = \frac{L}{V} DM$ represent in chromatography?
- Column efficiency calculation
- Mobile phase velocity calculation
- Retention time calculation
- Band broadening as a result of longitudinal diffusion (correct)
In which chromatography is longitudinal diffusion not very important except at low flow rates?
In which chromatography is longitudinal diffusion not very important except at low flow rates?
What contributes to mass transfer diffusion in chromatography?
What contributes to mass transfer diffusion in chromatography?
Which type of chromatography involves a stationary phase that is chemically & permanently held to a porous solid?
Which type of chromatography involves a stationary phase that is chemically & permanently held to a porous solid?
In which type of chromatography is the mobile phase a gas?
In which type of chromatography is the mobile phase a gas?
Which type of liquid chromatography has a stationary phase that is liquid held on a solid support as a thin coat?
Which type of liquid chromatography has a stationary phase that is liquid held on a solid support as a thin coat?
In which type of liquid chromatography is the stationary phase solid, porous with small particle size, and held in a column or spread on a plate?
In which type of liquid chromatography is the stationary phase solid, porous with small particle size, and held in a column or spread on a plate?
What is the mobile phase in gas chromatography?
What is the mobile phase in gas chromatography?
In which type of liquid chromatography is the stationary phase chemically & permanently held to a porous solid?
In which type of liquid chromatography is the stationary phase chemically & permanently held to a porous solid?
Which type of chromatography involves chromatographic separations taking place inside a column?
Which type of chromatography involves chromatographic separations taking place inside a column?
What is the nature of the mobile phase in supercritical fluid chromatography (SFC)?
What is the nature of the mobile phase in supercritical fluid chromatography (SFC)?
What distinguishes liquid solid chromatography (LSC) from liquid liquid chromatography (LLC)?
What distinguishes liquid solid chromatography (LSC) from liquid liquid chromatography (LLC)?
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Study Notes
Zone Broadening in Chromatography
- Zone broadening is influenced by multiple factors including longitudinal diffusion, mass transfer diffusion, and eddy diffusion.
- Longitudinal diffusion depends on the time it takes for molecules to diffuse along the direction of flow.
Longitudinal Diffusion Formula
- The formula (HL = \frac{L}{V} DM) represents the relationship between the longitudinal diffusion coefficients (D), linear velocity (V), and length (L) within a chromatography system.
Importance of Longitudinal Diffusion
- Longitudinal diffusion is not significant in high-performance liquid chromatography (HPLC), except at low flow rates where diffusion effects become more pronounced.
Mass Transfer Diffusion Contributions
- Mass transfer diffusion arises from the time taken for analyte molecules to equilibrate between the stationary and mobile phases, which can influence separation efficiency.
Stationary Phase in Chromatography
- In adsorption chromatography, the stationary phase is chemically and permanently bonded to a porous solid substrate.
Mobile Phase as Gas
- Gas chromatography utilizes a gas as the mobile phase, typically carrier gases like helium or nitrogen.
Thin Liquid Coating in Chromatography
- Thin-layer chromatography (TLC) employs a stationary phase consisting of a liquid coated on a solid support.
Stationary Phase in Solid-Phase Chromatography
- Solid-phase chromatography features a stationary phase that is solid, porous, with small particle size, and is retained in a column or laid out in a thin layer on a plate.
Mobile Phase in Gas Chromatography
- The mobile phase in gas chromatography is a gas that facilitates the separation of gaseous analytes.
Chemically Bound Stationary Phase
- In liquid chromatography, the stationary phase is often chemically bonded to a porous solid in processes such as reversed-phase and normal-phase chromatography.
Column Chromatography
- Column chromatography is characterized by chromatographic separations occurring inside a cylindrical column packed with stationary phase material.
Nature of Mobile Phase in SFC
- Supercritical fluid chromatography (SFC) uses supercritical fluids as the mobile phase, combining properties of gases and liquids for enhanced separation.
Distinction Between LSC and LLC
- Liquid-solid chromatography (LSC) involves a solid stationary phase attracting and retaining analytes, whereas liquid-liquid chromatography (LLC) utilizes a liquid stationary phase existing in equilibrium with a liquid mobile phase, distinguishing the two methodologies.
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