Chromatography Column Preparation Methods

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Questions and Answers

What is the primary function of the sintered glass disk in a chromatographic column?

To allow for the elution of the sample

To provide a smooth and even surface (correct)

To increase the surface area of the stationary phase

To prevent the stationary phase from getting mixed with the mobile phase

What is the main principle of separation in column chromatography?

Differential affinity towards the stationary and mobile phases (correct)

Differential solubility in the mobile phase

Differential molecular weight of the sample components

Differential boiling points of the sample components

What is the purpose of the tap at the bottom of a chromatographic column?

To introduce the mobile phase into the column

To pack the stationary phase into the column

To allow for the elution of the sample (correct)

To collect the separated components

What is the term for the property of how well a component of the mixture sticks to the stationary phase?

Adsorption Signup and view all the answers

What is the result of higher adsorption of a component to the stationary phase?

Slower movement through the column Signup and view all the answers

What is the term for the property of how well a component of the mixture dissolves in the mobile phase?

Solubility Signup and view all the answers

What is the benefit of using a sintered glass disk in a chromatographic column?

To prevent the adsorbent from passing out of the column Signup and view all the answers

How many methods are there for packing a chromatographic column?

Two Signup and view all the answers

What is the purpose of adding a small amount of pure sand above the stationary phase?

To prevent the disruption of the stationary phase Signup and view all the answers

What is the advantage of using a separatory funnel containing the eluent in the column?

It ensures continuous flow of the eluent Signup and view all the answers

What is the type of elution where a mixture of two solvents is used?

Gradual Elution Signup and view all the answers

What is the purpose of preparing the slurry of adsorbent with the eluent?

To prepare the adsorbent for separation Signup and view all the answers

What is the disadvantage of the dry packing method?

Any defect that is formed cannot be corrected Signup and view all the answers

What is the ratio of adsorbent to eluent used in preparing the slurry?

1-3 or 1-4 Signup and view all the answers

What is the purpose of allowing the mobile phase to pass through the lower end of the column?

To remove the air bubbles in the column Signup and view all the answers

What is the type of elution where a solvent or a mixture of solvents is used from the beginning to the end of the procedure?

Simple Elution Signup and view all the answers

What is the recommended ratio of sample to adsorbent for achieving good separation?

1:50 Signup and view all the answers

What is the primary purpose of vaporization in gas chromatography?

To convert the sample into a gas phase Signup and view all the answers

What is the role of the carrier gas in gas chromatography?

To carry the sample components through the column Signup and view all the answers

What factor affects the flow rate of the eluent in chromatography?

Packing of the column and flow of the tap Signup and view all the answers

What is the advantage of using a finer particle size of adsorbent in chromatography?

It increases the surface area of the adsorbent Signup and view all the answers

What is the purpose of the chromatographic column in gas chromatography?

To separate the sample components Signup and view all the answers

What is the result of using a ratio of 1:20 of sample to adsorbent in chromatography?

Good separation for a sample with 3 components Signup and view all the answers

What is the advantage of using ethyl acetate with 5% ethanol as a mobile phase in chromatography?

It increases the polarity of the mobile phase Signup and view all the answers

Study Notes

Column Chromatography

A separation technique where the stationary bed is placed within a tube
Stationary phase consists of very small particles or particles coated with a liquid
Columns are glass cylinders with a tap at one end and a disk of sintered glass above it
Benefits of sintered glass disk: smooth, even, and horizontal surface, prevents adsorbent from passing out of the column

Types of Column Chromatography

Ordinary adsorption chromatography
Gel filtration
Ion exchange chromatography

Principles of Separation

Differential affinities of components towards stationary and mobile phase
Affinity is dictated by adsorption and solubility properties of molecules
Higher adsorption to stationary phase = slower movement through column
Higher solubility in mobile phase = faster movement through column

Methods of Packing the Column

Dry packing method: introducing dry powder adsorbent with vibration or special piston
Wet packing method: preparing slurry of adsorbent with eluent, then pouring into column

Wet Packing Method Steps

Place small amount of mobile phase in column to remove air bubbles
Prepare slurry of adsorbent with eluent (ratio 1:3 or 1:4)
Pour slurry into column and allow it to settle
Remove excess mobile phase
Add small quantity of pure sand above stationary phase
Introduce sample dissolved in minimum amount of eluent
Open lower end to start separation
Ensure continuous flow of eluent without drying the column

Types of Elution

Simple Elution: using one solvent or a mixture from start to end
Fractional or Step-wise Elution: changing mobile phase during procedure
Gradual Elution: using a mixture of two solvents with gradual change

Factors Affecting Separation

Size of sample to amount of adsorbent used (ratio 1:50 yields best separation)
Size of column (length to diameter)
Flow rate (1ml/min yields good separation)
Choice of eluent
Nature of sample and adsorbent
Choice of adsorbent (activity and particle size)

Gas Chromatography (GC)

Analytical technique for separating and analyzing volatile compounds
Widely used in various fields (chemistry, pharmaceuticals, environmental science, food and beverage analysis, forensics)

Gas Chromatography Steps

Sample Introduction: introducing sample containing mixture of compounds to be analyzed
Vaporization: vaporizing sample before entering chromatographic system
Separation: injecting vaporized sample into chromatographic column
Mobile Phase (Carrier Gas): flowing carrier gas through the column, carrying sample components through the column

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Description

This quiz covers the methods of preparing chromatography columns, including dry packing and wet packing techniques, and their respective advantages and disadvantages.