Chromatogram of pure samples of food colours X, Y and Z is given in figure 1. Three samples of same food materials A, B, C are analyzed for purity, with the help of the chromatogram in figure 2. Identify the impure sample.

Let us compare the two chromatogram diagrams.

By comparison X, Y, Z with A, B, C food samples, we can conclude that sample ‘C’ is impure. Because there are two spots are found about ‘C’. Hence, one is pure and another one is impure.