Simple and Rapid HPLC-ICP-MS Method for the Simultaneous Determination of Cr(III) and Cr(VI) by Combining a 2,6-Pyridinedicarboxylic Acid Pre-Complexation Treatment

A simple and rapid analytical method was developed for the simultaneous determination of two chromium species, Cr(III) and Cr(VI), in the environmental waters by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). This study incorporated a chelating pretreatment with 2,6-pyridinedicarboxylic acid (PDCA) to convert Cr(III) species into a stable Cr(III)-PDCA anion complex, which was then separated from Cr(VI) oxyanion using an anion exchange column. Building on the fundamental analytical approach proposed by Shigeta <i>et al</i>. (doi: 10.2116/analsci.18P012), the mobile phase was optimized to ensure stability for ICP-MS detection, avoiding nonvolatile salts. Chromium species and chloride ions were effectively separated within 6 minutes at a flow rate of 0.6 mL min^-1 with the optimized mobile phase, which consisted of 50 mmol L^-1 ammonium acetate (pH 6.80) and 2 mmol L^-1 PDCA. The detection limits were 0.18 μg L^-1 and 0.09 μg L^-1 for Cr(III) and Cr(VI), respectively, at <i>m/z</i> 52 under He collision mode.