Chromatography is a lab technique used to separate mixtures into individual components. This separation is based on differences in the solubility of chemicals (solutes) within the mixture.

Paper Chromatography for Amino Acids

Method:

1. Preparation: Place a small spot of the amino acid mixture on a line near the bottom of the chromatography paper and let it dry.
2. Setup: Place the paper in a solvent with the sample line above the solvent level.
3. Separation: As the solvent travels up the paper, the amino acids move at different speeds due to their distinct solubility, size, and charge, separating into distinct spots or bands. The resulting pattern is called a chromatogram.

Using Chromatography to Identify Amino Acids

1. Application: Place a spot of the unknown amino acid mixture on the baseline of the paper.
2. Standard Comparison: Place spots of known amino acids alongside the unknown sample for reference.
3. Separation: As the solvent moves up, each amino acid in the sample separates and travels at a unique rate based on its solubility, size, and charge.
4. Visualisation: After drying, spray the paper with ninhydrin, which reacts with amino acids to produce a visible blue-violet colour.
5. Identification: Compare the unknown spots with known standards to identify amino acids present in the sample.

Exam Tip:

Know how to interpret a chromatogram and understand how chromatography can identify specific amino acids in an unknown sample. This knowledge can be helpful in practical applications like determining the composition of biological samples or identifying additives in food.