The best method to sparate the mixture of ortho and para nitrophenol (1:1) is

Ortho nitro phenol and para nitro phenol are seperated by steam distillation.

→ Inter molecular hydrogen bonding increases the boiling point of the compound, where as intra molecular hydrogen bonding will not influence the boiling point of the compound.

→ In case of para nitro phenoldue to inter mplecular hydrogen bonding it boils at high temperature hence rate of vapourisation is slow,and it remains in the distillation flask only,where as ortho nitro phenol boils at low temperature only and easily vapourises out and seperated from para nitro phenol.