Chromatography Questions

Question 1

Stationary Phase

Answer 1

• the phase that does not move with the sample, which the components of the mixture are place to be separated.
• e.g) silica gel or glass
• POLAR

Question 2

Mobile Phase

Answer 2

• the mobile phase is the solvent that moves through the paper, carrying different substances with it.
• e.g) water, methanol, ethanol
• NON-POLAR

Question 3

Retention Time

Answer 3

• a measure of the time taken for a solute to pass through a chromatography column

Question 4

Retention Factor (Rf Value)

Answer 4

• The Rf value of a compound is equal to the distance traveled by the compound divided by the distance traveled by the solvent front (both measured from the origin).

Question 5

Anaylte/Solute

Answer 5

• the substance being separated during chromatography

Question 6

Eluent/Solvent

Answer 6

• the mobile phase in chromatography,
• i.e; the solvent in the developing tank.

Question 7

How does the seperation of mixtures in chromatography relate to solubility and adsoprtion of components on the stationary phase?

Answer 7

• The stronger the adsorption of a component onto the stationary phase, the slower it moves. If the compound is attracted more towards the stationary phase then it will be more polar thus being adsorbed into the stationary phase

Question 8

Qualitative Analysis

Answer 8

• what chemical is present in the sample?
• We Use Retention Time

Question 9

Quantitative Analysis

Answer 9

• How much of each chemical is present?
• We Use standard solutions and calibration curves

Question 10

What Chromatography technique to use for:

Monitoring of air pollution

Answer 10

• GC

Question 11

What Chromatography technique to use for:

Monitoring of water pollution

Answer 11

• HPLC

Question 12

What Chromatography technique to use for:

Drug testing of urine and blood samples

Answer 12

• HPLC

Question 13

What Chromatography technique to use for:

Testing for food additives and quality

Answer 13

• HPLC or GC

Question 14

What things in particular to consider when justifying chromatography techniques?

Answer 14

• the properties of the substances being seperated
• the amount of substance available for analysis
• the sensitivity of the equipment

Question 15

Advantages, disadvantages and sensitivity of TLC

Answer 15

• limited sensitivity
• cheap, basic equipment and easy to do
• poor precision and accuracy

Question 16

Advantages, disadvantages and sensitivity of HPLC & GC

Answer 16

• high sensitivity and precise
• small sample size and readily automated
• moderately expensive instrument and a trained technician needed to operate

Question 17

Rf Value

Answer 17

the distance traveled by the compound
(DIVIDE)
the distance traveled by the solvent front