The amino acids that are separated from the column should be quantitated by heating them with ninhydrin, which forms purple-coloured compounds.

The amount of each amino acid is determined spectrophotometrically by measuring the absorbance of the amino acid derivatives, which is recorded continuously, on a chart recorder or fed directly into a computer for quantitative analysis. Each peak corresponds to an individual amino acid. The analysis described above is usually performed by using an amino acid analyser, an automated machine, which is described in Figure 3.19

Figure 3.19 Diagrammatic Representation of Amino Acid Analyser