# A quality control technician is investigating two samples of a yellow food colouring. Sample P produces a single spot when analysed by paper chromatography in three different solvents. Sample Q produces three separate spots in the same solvents. Explain what these results tell the technician about Sample P and Sample Q, and describe how paper chromatography separates the components in Sample Q.

> Eduqas A-Level Chemistry — 1.3 Chemical bonding · Explain · 5 marks

> Paper chromatography is used in the food industry to check whether colourings contain a single substance or a mixture of substances.

## Mark scheme (5 marks)

1. Sample P is a pure substance / contains only one compound or element
2. A pure compound produces a single spot in all solvents (so one spot confirms purity)
3. Sample Q is a mixture / contains more than one compound
4. In paper chromatography the solvent (mobile phase) carries the components up the paper (stationary phase)
5. Components separate because they have different solubilities in the solvent / the more soluble a substance is, the further up the paper it travels

## Key terms

- [paper chromatography](https://www.gradenine.co.uk/glossary/paper-chromatography)

## Related

- [Revision notes for Eduqas A-Level Chemistry](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-quality-control-technician-is-investigating-0dc2efea) · Published by Druglandscape Ltd.