18 Questions
What greatly influences the column efficiency in chromatography?
Length of the column
What is the popular mode of separation used in HPLC?
Partition
What is the mobile phase in gas chromatography?
Inert gas (He or N2)
What is the gold standard for analyzing volatile organic components (VOCs)?
Gas chromatography
What are the parts per billion used to detect in gas chromatography?
Compounds
What is the most powerful separative method recognized in chromatography?
Gas chromatography
What is the purpose of the retention factor (Rf) in column chromatography?
To calculate the ratio of distance traveled by the solute to the distance traveled by the solvent.
How is spot visualization achieved in thin layer chromatography?
Using a UV Lamp.
What is the purpose of derivatization in chromatography?
To carry out specific chemical reactions before or after chromatography for visualization purposes.
What is the role of iodine vapor in chromatography?
To form a colored complex for visualization purposes.
How is a dark burned area produced in chromatography?
By reacting with sulfuric acid.
What does a constant Rf value for a compound indicate?
It reflects the distribution coefficient for that compound under standard conditions.
What is the main principle behind adsorption chromatography?
Equilibriation between the mobile and stationary phases
Describe the principle behind partition chromatography.
Separation based on differences in solubility of sample components in the stationary phase or between mobile and stationary phases
Give an example of a technique that falls under partition chromatography.
Paper chromatography (PC)
What is the role of a thin film in partition chromatography?
Formed on the surface of a solid support by a liquid stationary phase
What factors should be considered when carrying out paper chromatography?
Apparatus, preparation of the sample, development of the chromatogram
How does column chromatography differ from paper chromatography?
Column chromatography uses a vertical column for separation, while paper chromatography uses a paper strip.
Study Notes
Adsorption Chromatography
- Acyl carbon chains of varying length are chemically bonded to the polar absorbent in adsorption chromatography
- The mobile phase consists of solvents such as methanol, butanol, and n-hexane
- Caprylic acid is one of the solutes used in adsorption chromatography
- Quercetin is another solute used in adsorption chromatography
- The retention factor (Rf) is the ratio of the distance traveled by the solute to the distance traveled by the solvent
- Rf value is specific and constant for a particular compound and reflects the distribution coefficient for that compound under standard conditions
Paper Chromatography
- Paper chromatography is a technique used in adsorption chromatography
- It involves spotting a sample on a stationary phase and allowing it to develop
- The distance traveled by the solute is compared to the distance traveled by the solvent to calculate the Rf value
- Visualization techniques are used to detect separated components, including iodine vapor and UV lamps
- Some components may not be visible and require derivatization or other visualization methods
Partition Chromatography
- Partition chromatography separates solutes based on differences in solubility between the mobile and stationary phases
- It is a type of liquid chromatography (LC)
- Paper chromatography is an example of partition chromatography
- The separation of a mixture is dependent on differences in partition coefficients of the components between an aqueous and immiscible organic liquid
- Partition chromatography involves a thin film formed on the surface of a solid support by a liquid stationary phase
- Solute equilibrates between the mobile phase and the stationary liquid
Gas Chromatography
- Gas chromatography is a type of partition chromatography
- The mobile phase is a gas (carrier gas)
- Partitioning components of a chemical mixture occur between the moving gas and stationary liquid phase
- Gas chromatography is recognized as one of the most powerful separative methods available
- It can detect very low amounts of compounds (parts per billion) and is the gold standard for volatile organic components (VOCs) analyses
Test your knowledge on adsorption chromatography and retention factor calculations. Understand the process involving chemically bonded acyl carbon chains and different mobile phases like methanol, butanol, and n-hexane. Learn how to calculate the retention factor for solutes like caprylic acid and quercetin.
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