This application note describes the use of LC(IC)-ICP-MS for low-level speciation analysis of Cr(III) and Cr(VI).
Chromium exists primarily as trivalent Cr(III) or hexavalent Cr(VI), which have different toxicological properties. This document details a routine, highly sensitive method to determine both species in various sample types using anion exchange liquid chromatography (LC/IC) coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The method utilizes the Agilent 7700x ICP-MS equipped with the Octopole Reaction System (ORS) operated in helium mode to remove matrix-based interferences.
The study demonstrates the analysis of mineral waters and California tap water. It reports detection limits below 200 ng/L for both species under standard conditions, and down to 0.008 pg/L for Cr(VI) alone using an optimized method with larger injection volumes. The document provides specific operating parameters for the HPLC and ICP-MS instruments used in the experiments.
| Column dimensions | 4.6 mm x 30 mm |
|---|---|
| Flow rate | 1.2 mL/min |
| Injection volume (standard) | 100 µL |
| RF power | 1550 W |
| Carrier gas flow rate | 1.05 L/min |
| Cell gas type and flow | He at 4 mL/min |
| Detection limit (Cr(VI) optimized) | ~0.008 pg/L |
The ORS collision/reaction cell is operated in helium mode to remove matrix-based polyatomic interferences such as ArC and ClO.
The detection limit for Cr(VI) was reduced to 0.008 pg/L.
The analysis is rapid, taking only about 3 minutes.