This document describes a method for measuring chromium content. This method can separate and measure Cr(III) and Cr(VI), and provide an indication of the toxicity of Cr content in a sample.
The document presents an optimized analytical method to determine the concentrations of trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)) in natural samples. This is critical because Cr(VI) is toxic while Cr(III) is essential, requiring separate measurement for accurate toxicity assessment.
The proposed technique couples Ion Chromatography (IC) with Octopole Reaction Cell ICP-MS. The method utilizes an optimized sample stabilization protocol involving EDTA and incubation to maintain species integrity. It employs a specific IC column (Agilent part number G3268A) and mobile phase conditions to separate the Cr(III)-EDTA complex from Cr(VI). Detection is performed using the Agilent 7500ce ICP-MS in He cell gas mode to remove interferences, achieving detection limits below 20 ng/L.
| Column Part Number | G3268A |
|---|---|
| Mobile Phase Composition | 5 mM EDTA (2Na), pH 7 |
| Flow Rate | 1.2 mL/min |
| Column Temperature | Ambient |
| Injection Volume Range | 50-500 uL |
| Reaction Temperature | 40 C |
| Incubation Time | 3h |
| EDTA Concentration in Mobile Phase | 5-15 mM |
Detection limits (DLs) of <20 ng/L were obtained for the individual Cr species.
The Agilent 7500ce ICP-MS uses He cell gas mode to remove ArC and C1OH interferences.
Complete conversion occurs after less than 1 hour at 60 C or 3 hours at 40 C.