Quantitation of 1,2 and 1,4-naphthoquinone in phthalic anhydride by HPLC

Summary A simple method of analysis of the 1,2 and 1,4 isomers of naphthoquinone in crude phthalic anhydride has been developed. The sample was first dissolved in water at 60°C to quantitatively hydrolyse the anhydride to phthalic acid.Analysis of the aqueous solution by reversed-phase HPLC using 7525 methanol:water mobile phase resulted in excellent resolution between the phthalic acid and the naphthoquinones and enabled quantitative measurement of each of the naphthoquinones to 0.1 % in crude phthalic anhydride.