Primary, secondary and tertiary amines can be separated using:

The Hinsberg test, which uses para-toluenesulphonyl chloride ($$\text{TsCl}$$, also called tosyl chloride), is the standard method to distinguish and separate primary, secondary, and tertiary amines.

When a primary amine reacts with $$\text{TsCl}$$, it forms a sulphonamide $$\text{R-NH-Ts}$$ that still has an acidic N-H hydrogen. This product dissolves in aqueous NaOH to form a soluble sodium salt, and can be separated from the mixture.

A secondary amine also reacts with $$\text{TsCl}$$ to form a sulphonamide $$\text{R}_2\text{N-Ts}$$, but this product has no N-H hydrogen, so it does not dissolve in NaOH. It remains as an insoluble solid, which can be filtered off.

A tertiary amine does not react with $$\text{TsCl}$$ at all (it has no N-H bond), so it remains unchanged in solution.

Since all three classes of amines give different, physically separable products, para-toluenesulphonyl chloride can be used to separate primary, secondary, and tertiary amines. The correct answer is Option A.