- Rf value
- The ratio of the distance moved by a substance to the distance moved by the solvent front. Always between 0 and 1, no units.
- Stationary phase
- The medium that does not move in chromatography (e.g. the paper or the silica gel on a TLC plate).
- Mobile phase
- The solvent that moves through the stationary phase, carrying dissolved substances with it.
- Instrumental analysis
- The use of scientific instruments to identify and quantify substances, as opposed to traditional bench chemistry.
- Flame emission spectroscopy
- An instrumental method in which a sample is vaporised in a flame and the emitted light is analysed as a line spectrum to identify metal ions.
- Line spectrum
- A pattern of coloured lines at specific wavelengths, unique to each element, produced when excited electrons return to their ground state.
This definitions covers Key Terms within Instrumental Analysis for GCSE Chemistry. Revise Instrumental Analysis in Chemical Analysis for GCSE Chemistry with 6 exam-style questions and 6 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 7 of 12 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Practice questions for Instrumental Analysis
Which formula correctly calculates the Rf value in chromatography?
State two advantages of using instrumental methods of analysis compared with traditional chemical tests.
Quick recall flashcards
What is the formula for calculating the Rf value in chromatography?
Rf = distance moved by substance ÷ distance moved by solvent front
Always between 0 and 1. No units.
In paper chromatography, what does the number of spots on a chromatogram tell you about purity?
One spot → pure substance (single component)
Multiple spots → mixture / impure sample (multiple components, each with different Rf)