Determination of Cr(VI) in rice using ion chromatography inductively coupled plasma mass spectrometry

Abstract

Determination of Cr(VI) in rice is reported using ion chromatography (IC) and dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS). Cr(VI) is separated from other Cr species within 4.5 min using NH₄NO₃ solution at pH 8.8 as mobile phase. Spectral interferences on ⁵²Cr⁺ are minimized with NH₃ in DRC. The detection limit of (LOD) Cr(VI) is 0.06 ng mL^-1. This methodology is utilized for the determination of Cr(VI) in different rice samples and can also be applied for screening of rice for toxicity with respect to Cr. The Cr species are leached from rice powder into 5% (v/v) tetramethyl ammonium hydroxide (TMAH) solution in an ultrasonic bath. The extracts are analyzed by IC-DRC-ICP-MS for Cr(VI). Spike recoveries of Cr(VI) are 98-102% and precision between sample replicates is better than 6.3%. No Cr(III) is converted to Cr(VI) during extraction. Cr(VI) is present in all the rice samples analyzed.

Keywords: Alkaline extraction; Chromate [Cr(VI)]; Inductively coupled plasma mass spectrometer; Ion chromatography; Rice; Ultrasonic extraction.