Determination of Cr³⁺, CrO₄ ^2–, and Cr₂O₇ ^2– in environmental matrixes by high-performance liquid chromatography with diode-array detection (HPLC–DAD)

Abstract.

A high-performance liquid chromatographic method with diode array detection (HPLC–DAD), based on chelation with ammonium pyrrolidinedithiocarbamate (APDC), has been developed for the determination of chromium species. Determination of Cr³⁺, CrO₄ ^2–, and Cr₂O₇ ^2– was performed for standards and synthetic environmental matrixes. This method is robust, rugged, and can be used for rapid routine determination of chromium species with high precision and reliability. Sample pretreatment is simple. The method is capable of discriminating not only between Cr(III) and Cr(VI) but also between the chemical forms of Cr(VI) – CrO₄ ^2– and Cr₂O₇ ^2–. By analysis of numerous samples the method has been shown to be selective, sensitive, and free from matrix interference, which is crucial for the determination of chromium species in difficult-to-analyze environmental matrixes. This method has been validated by means of an interlaboratory study. Although different speciation techniques were used during this study, there was good agreement between results from the two laboratories. The method detection limits were 7 and 4 mg L^–1 for Cr³⁺ and Cr₂O₇ ^2–, respectively. Recoveries of the analytes from spiked samples were 98% and 100% for Cr³⁺ and Cr₂O₇ ^2–, respectively. Both were based on a 10-mL sample volume spiked with 0.4 mg L^–1 chromium.