Don't know if you got an answer yet or not but...
I'm a Scottish candidate but the answer I would give to that (having done a test on it 2 weeks ago only) would be you could use Thin Layer Chromatography. If it was a pure sample then only one spot would appear on the chromatogram.
Also, Determination of the melting point can give an indication of the purity of a compound, as the presence of impurities lowers the melting point and broadens its melting temperature range. Since impurities lower the melting point, the technique of mixed melting point determination
can be used to confirm the identity of a solid.
But your best bet is to use TLC.Hope that helps