A simple method has been proposed for the determination of chromium species by high-performance liquid chromatography (HPLC) after preconcentration by the ionic liquid, 1-butyl-3-methyimidazolium hexafluorophosphate ([C 4MIM][PF 6]). The simultaneous preconcentration of Cr(VI) and Cr(III) in wastewater was achieved with ammonium pyrrolidinedithiocarbamate (APDC) as the chelating agent and the ionic liquid [C 4MIM][PF 6] as the extractant. Baseline separation of the APDC chelates of Cr(III) and Cr(VI) was realised on a RP-C18 column using a mixture of methanol–acetonitrile–water (53:14:33, v/v) as the mobile phase at a flow rate of 1.0 mL min − 1 . The influences of several variables on the complexation and extraction were evaluated: pH, reaction time, APDC concentration and metal ion interference. Our results showed that when the linear concentration of Cr(VI) and Cr(III) ranged from 25 to 200 μg L − 1 , their linear correlation coefficients were between 0.9977 and 0.9978, their recoveries ranged from 91.8% to 95.8% and their relative standard deviations (n = 3) were between 0.31% and 1.8%. Common metal ions in water did not interfere with the determination. This method is a simple, fast, accurate, highly stable and selective method and has successfully been applied to the speciation of chromium in wastewater.