# A pharmaceutical company uses gas chromatography (GC) followed by mass spectrometry (MS) to analyse a new pain-relief tablet. Explain how GC-MS works to identify the components present in the tablet, and why this technique is preferred over traditional chemical tests for this purpose.

> Edexcel A-Level Chemistry (9CH0) — Topic 6 Modern analytical techniques · Explain · 5 marks

> A pain-relief tablet is dissolved in a solvent and the resulting solution is injected into a GC-MS instrument. The instrument produces a chromatogram showing several peaks, and a mass spectrum is recorded for each peak.

## Mark scheme (5 marks)

1. In gas chromatography, the sample is carried through a column by a carrier gas
2. Different components travel through the column at different speeds / are separated because they interact differently with the stationary phase, so they exit at different times (different retention times)
3. Each separated component is then passed into the mass spectrometer, which identifies it by its mass spectrum / molecular ion peak / fragmentation pattern
4. The mass spectrum of each component is compared to a database / library of known spectra to identify the substance
5. GC-MS is preferred because it can identify very small quantities / traces of substances (high sensitivity) and can analyse complex mixtures simultaneously, which traditional chemical tests cannot do as reliably or quickly

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-pharmaceutical-company-uses-gas-chromatography-1a3a6790) · Published by Druglandscape Ltd.