This is to certify that MR/MRS_____________________ A student of class______________________ has successfully completed the research on the below project under the guidance of MR/MRS (Subject Teacher).
SIGNATURE OF EXTERNAL
SIGNATURE OF CHEMISTRY TEACHER.
- MATERIAL REQUIRED
To separate the color components present in the sketch pen (given below).thus find the Rf value.
Chromatography is a laboratory technique for the separation of a mixture. The various constituents of a mixture travel with the different speeds.chromatography may be preparative or analytical. The purpose of preparative chromatography is to separate the components of a mixture for advance purpose. whereas analytical chromatography is done normally with the smaller amount of material for measuring the relative proportions of analytes in a mixture.
chalk chromatography ,there is a stationary phase which is the chalk and a mobile phase which is the liquid solvent (or mixture of solvents)use to carry the sample solutes under analysis along the chalk .usually ,one uses chromatography to find out the components of a sample which are separated depending how much soluble these are in particular solvents and how far they travel along the chalk.
In order to make this technique more scientific rather than a mere interpretation by sight ,the retention value (Rf value for short) was applied in chromatography. A particular compound will travel the same distance along the stationary phase by a specific solvent (or solvent mixture) given that other experimental conditions are kept constant.
The Rf value is defined as the ration of the distance moved by the solute (i.e. the dye or pigment under test) and the distance moved by the solvent (known as the solvent front ) along the chalk, where both distances are measured from the common origin or application baseline, that is the point where the sample is initially spotted on the paper.
Rf value= distance travelled by the solute/distance travelled by the solvent
- Sketch pens(green, brown ,black)
- Three chalks
- Take a chalk of approximately 6cm
- Draw a horizontal line from pencil at a distance of 1cm from the base of the chalk .mark a point with a pencil on the line drawn
- Spot the color ink directly with a sketch pen at a point marked before. Care should be taken that the spot is small in size . Repeated spotting may be done to enrich the spot, to increase the concentration of component.
- Take a clean beaker and fill it with 1-2 ml of water. there should be no droplets sticking inside the walls of beaker.
- Insert the chalk carefully in the beaker so that only the spot n the chalk remains above the solvent(water)
- Keep the beaker in safe place and leave it undisturbed .
- Notice the rise of the solvent and the components in the upward direction.
- After sometimes, the spot will separate into different colors and the solvent moves ahead of the colours
- Remove the chalk from the beaker .dry the chalk and mark the levels of the solvent and colour spots from the different line drawn before.
- Record the observation in the tabular form.
- Calculate the Rf value for the various components.
|Distance travelled |
|Distance travelled by |
- Pharmaceutical company – determine amount of each chemical found in a new product.
- Hospital – detect blood or alcohol levels in a patient’s blood stream
- Law enforcement – to compare a sample from suspects.
- Environmental agency – determine the level of pollutants in the water supply.
- Manufacturing plant – to purify a chemical needed to make a product.
- Biotechnology industry – establishing the purity or concentration of compounds in biotechnological research.
- biological application – used to separate and identify amino acid, carbohydrates, fatty acid, and other natural substance.
- Press gently while spotting the chalk otherwise the chalk particle will be stuck on the sketch pen nib.
- Spot must not big in size.
- Spot must be enriched by spotting at the same point twice or thrice.
- The spot should never be dipped in the solvent.
- There should be no water droplets sticking to the inside of the beaker.
- The solvent should be adequate.
- Rf value is to be calculated by measuring maximum height of the colored spot.
- FOR DEMO; click here