The ethyl esters of terephthalic acid,p toluic acid and the internal standard,octane diacid are obtained from the reaction of iodoethane with tetra methyl ammonium salts of the corresponding acids.The ethyl esters can be well separated by SE 30 0.53mm capillary column.This method was used for the determination of p phthalic acid in purified product of p toluic acid.The relative standard deviation and the recovery of the method are 4.55 and 93%～103%,respectively.
