Cambridge O Level Chemistry · Syllabus 5070 · Experimental Techniques and Chemical Analysis
Paper Chromatography
What is Paper Chromatography?
A method for separating a mixture of soluble substances. Small concentrated spots of the mixture are placed on a pencil baseline near one end of a piece of chromatography paper, and the paper is stood in a suitable solvent with the solvent level below the baseline. The solvent travels up the paper and carries the substances with it by different amounts, so they separate into individual spots. Substances that are colourless are made visible with a locating agent.
This definition is part of the Experimental Techniques and Chemical Analysis chapter in Cambridge O Level Chemistry.
Paper Chromatography in context
Experimental techniques and chemical analysis cover how a chemist gathers and interprets evidence: choosing the right apparatus for a measurement, running a titration to find a reacting volume, using paper chromatography to separate and identify substances, separating and purifying mixtures by filtration, crystallisation or distillation, and running the qualitative analysis tests that identify anions, cations, gases and metal ions. A titration uses a volumetric pipette to measure a fixed volume and a burette to add a variable volume until an indicator shows the end-point, giving a titre as final reading minus initial reading. Chromatography separates soluble substances by how far they travel in a solvent, measured as the retention factor, Rf.