chromatography

Question 1

what is chromatography

Answer 1

a technique that can be used to separate a mixture into its individual components

Question 2

what mixtures can be separated by chromatography

Answer 2

carbohydrates
proteins
vitamins
nucleic acids

Question 3

what are the two phases in chromatography

Answer 3

mobile phase
stationary phase

Question 4

outline the principals and process of paper/thin-layer chromatography

Answer 4

• use capillary tube to spot solution onto pencil ‘start line’ (origin) 1cm above bottom of paper
• place chromatography paper in solvent (origin should be above solvent level)
• allow solvent to run until it almost touches other end of the paper. Molecules in mixture move different distances based on relative solubility in solvent/attraction to paper

Question 5

what are Rf values? how can they be calculaed

Answer 5

ratios that allow comparison of how far molecules have moved in chromatograms
- Rf value = distance between origin and centre of pigment spot / distance between origin and solvent front

Question 6

what is the term TLC

Answer 6

thin layer chromatography

Question 7

why should you wear gloves/use forceps when holding the TLC plate

Answer 7

to prevent oils from your finger affecting how far the mixture travels

Question 8

why do you draw the origin line in pencil and not pen

Answer 8

pencil is insoluble
pen ink will dissolve in the solvent and contaminate

Question 9

why do you ensure solvent is below the height of origin line

Answer 9

so that the solvent to