Abstract: A high performance liquid chromatographic method has been developed for the simultaneous determination of 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, 3-chlorophthalic acid and 4-chlorophthalic acid. The operating conditions were a Luna-C18 column at 30 ℃, methanol-0.15 mol/L ammonium dihydrogen phosphate solution (42∶58, v/v) as mobile phase with flow rate of 0.8 mL/min, ultra-violet detection at 240 nm. An external standard method was used. Samples were esterified with absolute ethanol at 80-100 ℃ for 15 min. 3-Chlorophthalic anhydride and 4-chlorophthalic anhydride were respectively converted to two isomers of monochloro-O-carboxyl ethyl benzoate, and the monochlorophthalic acids were not esterified under the reaction conditions. The results demonstrated that the recoveries were 99.1%-101.5%; the relative standard deviations ranged from 0.48% to 0.87%; the linear ranges were 3.12-312.4 mg/L, 2.96-222.3 mg/L, 1.86-186.4 mg/L, 1.41-141.0 mg/L for 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, 3-chlorophthalic acid and 4-chlorophthalic acid, respectively. The method was simple, accurate and fast. The six components could be separated completely in about 20 min.

Key words: 3-chlorophthalic acid, 3-chlorophthalic anhydride, 4-chlorophthalic acid , 4-chlorophthalic anhydride, high performance liquid chromatography（HPLC）