Chromatography Techniques and Applications

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Questions and Answers

What does a pure sample show on a chromatogram?

A gradient of colors

One spot (correct)

Three or more spots

Two distinct spots

Paper chromatography can only separate color substances.

False (B)

Name one application of chromatography techniques.

To separate and identify types of sugars in fruit juice.

In chromatography, the substance that is attracted to the surface of the paper is said to be __________.

adsorbed Signup and view all the answers

Match the following types of chromatography with their characteristics:

Gas chromatography = Separates gases and volatile substances Thin layer chromatography = Uses a thin layer of adsorbent for separation Paper chromatography = Utilizes paper as the stationary phase High-performance liquid chromatography = Uses high pressure for improved separation Signup and view all the answers

Which of the following describes how substances are separated in chromatography?

Due to differences in solubility and adsorption (C) Signup and view all the answers

More strongly adsorbed substances move faster up the chromatography paper.

False (B) Signup and view all the answers

What is the mobile solvent in paper chromatography typically composed of?

Usually an organic solvent like ethanol, butanol, or a mixture of solvents. Signup and view all the answers

Which solvent is more effective at dissolving solutes that are less soluble in organic solvent?

Water (A) Signup and view all the answers

The solvent level must be above the pencil line to ensure proper chromatography.

False (B) Signup and view all the answers

What is the purpose of drawing a baseline on chromatography paper?

To serve as a starting point for applying the mixture and to prevent unwanted movement. Signup and view all the answers

The resulting chromatography paper with separated spots of colours is called a __________.

chromatogram Signup and view all the answers

Match the following terms with their definitions:

Solvent front = The line indicating the furthest point reached by the solvent Rf value = A ratio representing the distance traveled by solute to distance traveled by solvent front Adsorbed = The process of a substance sticking to a surface Capillary action = Movement of liquid through narrow spaces without external force Signup and view all the answers

What happens if the tiny spot of the mixture is too large?

It will smudge and lead to overlapping spots. (B) Signup and view all the answers

The Rf value changes depending on temperature and the solvent used.

True (A) Signup and view all the answers

Why is it important to cover the chromatography setup during the experiment?

To prevent wind currents that could cause rapid evaporation of the volatile solvent. Signup and view all the answers

Study Notes

Paper Chromatography

Chromatography separates colours, pigments, and dyes, now also colourless substances
Paper chromatography separates small amounts of similar substances
A chromatogram shows the separated components on the paper

Distinguishing Pure and Impure Samples

A pure sample produces only one spot on a chromatogram
Chromatography includes techniques like gas and thin-layer chromatography
Chromatography identifies tiny amounts of substances, potentially less than 1 picogram

Applications of Chromatography

Separates and identifies sugars (e.g., sucrose, maltose, glucose) in fruit juice
Separates and identifies amino acids in protein samples
Detects illegal drugs used in drinks/food
Detects illegal chemicals in food
Detects excessive drug use in athletes (e.g., steroids, beta-blockers) in urine samples
Screens national service personnel for drug use in urine samples

Principle of Chromatography

Dyes move at different speeds due to differences in
- Solubility in the solvent
- Adsorption on the paper
Greater solubility leads to faster movement and higher spot position
Different solutes have different solubilities, leading to separation

Procedure for Paper Chromatography

Draw a baseline on chromatography paper with a pencil
- Ink pens are not used as ink mixes with the solvent, leading to unwanted spots
Spot a small, dry sample of the mixture onto the base line, repeat 2-3 times
- Large, smudged spots produce overlapping spots and poor separations
Place the paper in a tube or beaker with solvent, upright using a support (e.g., cork)
- Solvent level needs to be below the baseline to prevent the ink mixture from dissolving
Allow the solvent to travel up the paper
- Solvent travels by capillary action
Remove the paper when the solvent nears the top, marking the solvent front
Spots are separated due to differing solubilities and adsorption rates.

Identifying Components

Components more soluble travel further from the start line than those less soluble
Similar components travel the same distance

Retention Factor (Rf)

Rf = distance travelled by solute / distance travelled by solvent front (constant at a set temperature)
Rf is unique for each substance, used to identify them
Rf values differ based on the solvent

Separating Colourless Substances

Locating agents react with colourless substances to reveal visible spots
- Ninhydrin reacts with amino acids to produce purple spots
- Silver nitrate/sodium hydroxide creates a brown spot for sugars
UV light can highlight colourless substances that fluoresce under UV light

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Description

This quiz covers the principles and applications of chromatography, particularly focusing on paper chromatography. It explores how substances are separated, the identification of pure versus impure samples, and various uses in detecting compounds in everyday items like food and urine samples.