Unit 2: Practical scientific procedures and techniques
Chromatography
I’m a newly appointed technical assistant at a chemical plant called; Chemcalequip. As part of
my induction tasks and to progress my role I need to demonstrate skills in a range of practical
procedures/techniques. Chromatography is a procedure used to separate and identify substances
within a mixture. There are many different chromatography types, each with the same aim but
other mobile and stationary phases. In paper chromatography, paper is used as the stationary
phase.
In thin layer chromatography, the stationary phase is a sheet of glass, plastic, or aluminum foil
coated with a thin layer of adsorptive material.
Using more polar solvents will cause the substances to move faster up the paper. This is because
increasing polarity will increase the attraction of polar molecules to polar phases. For example,
the stationary phase is typically polar meaning polar substances will adhere more to it and be
found lower down the chromatogram. The mobile phase used in chromatography must be
considered. For instance, using water (a polar substance) as a mobile phase will give different
results than using a less polar mobile phase. This is because polar substances dissolve in polar
water molecules. They mix readily because both types of molecules engage in hydrogen
bonding.
Chromatography is used in several industries such as forensics for DNA fingerprinting and
bioinformatics. Chromatography is also used in the food industry for separating and identifying
additives, vitamins, preservatives, proteins, and amino acids.
,I am aiming to ensure that the experiment is reliable and valid enough to compare to known
values or data from experiments that have already been carried out. This will enable me to test
the repeatability and reproducibility of the experiment.
Paper Chromatography Of Plant Pigments
Equipment:
Chromatography paper
Beaker
Measuring cylinder
Running solvent
Pencil
Ruler
Pestle and mortar
Propanone
Scissors
Hairdryer
Lid
Capillary tube
Pipette
, Health and safety:
Propanone is an irritant and flammable, can cause serious eye irritation and may cause skin
dryness/cracking. Wear safety goggles and gloves. Use a fume cupboard if possible and keep
away from naked flames.
Broken glassware can cause cuts. Glass fragments could be unnoticed and very dangerous. Clean
any broken glass and keep glassware at the centre of the table.
Running solvent is made up of five-part cyclohexane, three-part petroleum spirit, and two-part
propanone. It can be absorbed into the skin which causes irritation. Wear safety goggles and
gloves, wash off any running solvent that meets the skin.
Method:
1. Draw a horizontal line using pencil 3cm from the bottom of the chromatography paper.
The base line is drawn in pencil as drawing it in pen will affect the chromatogram due to the pen
ink being carried by the mobile phase.
2. Cut leaves using scissors and grind using a pestle and mortar. Add 5 drops of propanone.
Chromatography
I’m a newly appointed technical assistant at a chemical plant called; Chemcalequip. As part of
my induction tasks and to progress my role I need to demonstrate skills in a range of practical
procedures/techniques. Chromatography is a procedure used to separate and identify substances
within a mixture. There are many different chromatography types, each with the same aim but
other mobile and stationary phases. In paper chromatography, paper is used as the stationary
phase.
In thin layer chromatography, the stationary phase is a sheet of glass, plastic, or aluminum foil
coated with a thin layer of adsorptive material.
Using more polar solvents will cause the substances to move faster up the paper. This is because
increasing polarity will increase the attraction of polar molecules to polar phases. For example,
the stationary phase is typically polar meaning polar substances will adhere more to it and be
found lower down the chromatogram. The mobile phase used in chromatography must be
considered. For instance, using water (a polar substance) as a mobile phase will give different
results than using a less polar mobile phase. This is because polar substances dissolve in polar
water molecules. They mix readily because both types of molecules engage in hydrogen
bonding.
Chromatography is used in several industries such as forensics for DNA fingerprinting and
bioinformatics. Chromatography is also used in the food industry for separating and identifying
additives, vitamins, preservatives, proteins, and amino acids.
,I am aiming to ensure that the experiment is reliable and valid enough to compare to known
values or data from experiments that have already been carried out. This will enable me to test
the repeatability and reproducibility of the experiment.
Paper Chromatography Of Plant Pigments
Equipment:
Chromatography paper
Beaker
Measuring cylinder
Running solvent
Pencil
Ruler
Pestle and mortar
Propanone
Scissors
Hairdryer
Lid
Capillary tube
Pipette
, Health and safety:
Propanone is an irritant and flammable, can cause serious eye irritation and may cause skin
dryness/cracking. Wear safety goggles and gloves. Use a fume cupboard if possible and keep
away from naked flames.
Broken glassware can cause cuts. Glass fragments could be unnoticed and very dangerous. Clean
any broken glass and keep glassware at the centre of the table.
Running solvent is made up of five-part cyclohexane, three-part petroleum spirit, and two-part
propanone. It can be absorbed into the skin which causes irritation. Wear safety goggles and
gloves, wash off any running solvent that meets the skin.
Method:
1. Draw a horizontal line using pencil 3cm from the bottom of the chromatography paper.
The base line is drawn in pencil as drawing it in pen will affect the chromatogram due to the pen
ink being carried by the mobile phase.
2. Cut leaves using scissors and grind using a pestle and mortar. Add 5 drops of propanone.
