Separation of chromium(III) and chromium(VI) by reversed-phase ion-pairing chromatography

The separation of Cr(III) and Cr(VI) by reversed-phase ion pairing liquid chromatography for a specific purpose has been investigated. Chromium(III) was chelated with EDTA at pH = 6.0 prior to analysis. The mobile phase (pH = 6.0) consisted of a 0.32 mmol L–1 EDTA and 0.83 mmol L–1 tetrabutylammonium hydroxide. The method showed that Cr(III) and Cr(VI) were effectively separated at low mobile phase flow rate which is suitable for a future experiment design of isotopic ratio measurements. The most difficult task was not only to ensure the effective separation but also to avoid any possible inter-conversion between two chromium forms. For a better detection of chromium species, the chromatographic system was coupled with a typical quadrupole inductively coupled plasma mass spectrometry.