# A factory produces a batch of painkiller tablets. A quality control technician uses paper chromatography to check whether the active ingredient in the tablets is pure. Explain how the technician could use the chromatogram produced to determine whether the active ingredient is pure.

> AQA GCSE Chemistry (8462) — 4.8.2 Identification of common gases · Explain · 4 marks

> Paper chromatography is used in the pharmaceutical industry to check the purity of compounds in medicines.

## Mark scheme (4 marks)

1. A pure compound produces a single spot (in any solvent)
2. If more than one spot is produced, the active ingredient is impure / is a mixture
3. The Rf value of the spot can be compared to the known Rf value of the pure active ingredient
4. If the Rf value matches the reference / known value (and only one spot is seen), the active ingredient is confirmed as pure

## Key terms

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

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](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-factory-produces-a-batch-of-0b417c9f) · Published by Druglandscape Ltd.