Define the technique used to separate pure sample from an impure sample.
There are several methods to do this.
By heating we can separate the samples. If we have a mixture with two compounds that has different boiling points e can separate them by using the boiling point.
The same above can be done for defference in liquid points.
If some part of a mixture is soluble in a chemical and other not we can add respective chemicals to do the separation.
If some part of a liquid mixture can be precipitated using chemicals we can use that also for separation.
So many other methods are there but e must use the correct one for our sample.