# A food scientist uses paper chromatography to analyse the colouring agents present in two fruit drinks, A and B. After the experiment, the chromatogram shows several separated spots. Explain how the food scientist can use the chromatogram to determine whether the two drinks contain any of the same colouring agents.

> Cambridge International IGCSE Chemistry (0620) — 12.3 Chromatography · Explain · 4 marks

> Two fruit drinks, A and B, are tested by paper chromatography using the same solvent. The chromatogram is developed and the spots are marked.

## Mark scheme (4 marks)

1. Each spot travels a fixed distance from the baseline, giving an Rf value (or ratio of distances)
2. Rf value is calculated as distance moved by spot divided by distance moved by solvent front
3. Spots at the same Rf value (same height on the chromatogram) indicate the same colouring agent
4. The number of spots in each sample indicates the number of different colouring agents present

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-food-scientist-uses-paper-chromatography-c6b304c3) · Published by Druglandscape Ltd.