SEPARATION OF POSITIONAL ISOMERS OF NITROBENZOIC ACID BY REVERSED-PHASE LIQUID-CHROMATOGRAPHY WITH 2-PROPANOL-WATER-ACETIC ACID AS ELUENT

A method for the separation of o-, m- and p-nitrobenzoic acid was deve loped using reversed-phase liquid chromatography. A C-18 bonded column (150 mm x 4.6 mm I.D.) was used as stationary phase and 2-propanol-wa ter-acetic acid (20:80:0.4, v/v/v, pH 2.99) at a flow-rate of 1.2 ml/m in as eluent; the detection wavelength was 254 nm. The nitrobenzoic ac id isomers are separated with R-s greater than or equal to 1.5, the de tection limits (at 254 nm) of the o-, m- and p-isomers are 4, 7 and 5 mu g/ml, respectively. This method is very simple and reproducible.