Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Chromatography is an analytical technique used to separate and identify the components of a mixture based on their different solubilities in a mobile phase and their affinity for a stationary phase.
The Stationary Phase is a fixed material (such as chromatography paper or a silica-coated plate) that slows down the movement of components.
The Mobile Phase is a solvent (liquid or gas) that moves through the stationary phase, carrying the components of the mixture with it.
Components with higher solubility in the mobile phase and lower affinity for the stationary phase travel faster and further up the chromatogram.
A pure substance will yield only one spot on a chromatogram, whereas a mixture will separate into multiple spots.
If the substances being separated are colorless (e.g., amino acids), a locating agent such as ninhydrin or light is used to make the spots visible.
The (Retention Factor) value is a ratio used to identify substances; it is characteristic for a specific substance under a given set of conditions (same solvent and stationary phase).
Gas-Liquid Chromatography () is used for volatile organic compounds, where the mobile phase is an inert carrier gas like or and the stationary phase is a high-boiling point liquid on an inert solid.
📐Formulae
💡Examples
Problem 1:
In a paper chromatography experiment to identify a food dye, the baseline was drawn from the bottom of the paper. After the experiment, the solvent front had reached a point from the bottom of the paper. A specific blue dye spot was found from the bottom of the paper. Calculate the value for the blue dye.
Solution:
Explanation:
To calculate the value, we must measure the distance from the baseline (starting line), not the edge of the paper. Subtracting the offset gives the actual travel distance for both the solvent and the solute.
Problem 2:
A mixture containing two amino acids, and , is analyzed using . The values for and in the chosen solvent are and respectively. If the solvent front travels , calculate the distance between the two spots on the chromatogram.
Solution:
Explanation:
The distance moved by each component is found by multiplying the value by the solvent front distance. The separation is the absolute difference between these two calculated distances.