L5-(practical) Chromatography and monosaccharides

Paper chromatography can be used to separate a mixture of monosaccharides. Mixtures containing coloured molecules, such as ink or chlorophyll, do not have to be __1? as they are already coloured. Mixtures of colourless molecules, such as a mixture of monosaccharides, have to be __2? first.

1.Stained. 2.Stained

1. What is the stationary phase?

2.What is the mobile phase?

3.What is the Rf value ?

1.The part that stays put whilst the sample moves past it e.g. paper

2.The moving liquid or gas that carries your sample through the stationary phase e.g. water,ethanol

3.The Rf value measures how far a substance travels in a chromatogram

How do you work out the rf value?

Distance moved by substance ———————————————— Distance moved by solvent

How do we carry out the practical to separate a mixture of monosaccharides?

0.A pencil line is drawn near the bottom on chromatography paper (pencil is used because it won’t mix with the other mixtures)

1.A spot of the stained monosaccharide sample mixture is placed on a line at the bottom of the chromatography paper.

2. Spots of known standard solutions of different monosaccharides are then placed on the line beside the sample spot.

3. The chromatography paper is then suspended in a solvent.

4. As the solvent travels up through the chromatography paper, the different monosaccharides within the mixture separate out at different distances from the line.

5. The unknown monosaccharides can then be identified by comparing with the chromatograms of the known standard solutions of different monosaccharides.

6. If a spot from the monosaccharide sample mixture is at the same distance from the line as a spot from one of the known standard solutions, then the mixture must contain this monosaccharide.