NEMC: Chromium Speciation of Drinking Waters by IC-ICPMS

Importance of the Topic

Chromium exists in water primarily as trivalent Cr(III) and hexavalent Cr(VI), with dramatically different toxicological profiles. While Cr(III) is an essential micronutrient, Cr(VI) is a known carcinogen and reproductive toxicant. Accurate speciation of these forms in drinking water is vital for public health compliance and environmental monitoring.

Objectives and Study Overview

This study aimed to develop a rapid, sensitive, and interference‐free method for simultaneous determination of Cr(III) and Cr(VI) in various water matrices. Key objectives included:

• Establish isocratic ion chromatographic separation of chromium species without complex sample pretreatment.
• Couple ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP‐MS) for trace‐level detection.
• Validate method performance in tap water, well water, and multi‐element standards.

Methodology

Samples were analyzed directly without derivatization or chelation. An isocratic mobile phase of 9 mM HNO₃ (pH 2.0) at 0.3 mL/min was used on a Shodex™ VC‐50 2D column at 50 °C. A 20 µL injection volume provided full separation within 10 minutes. Chromium species were detected at m/z 52 on an ICP‐MS with a helium collision cell to remove polyatomic interferences such as ArC and ClOH.

Instrumentation Used

• Shimadzu Prominence IC: inert flow path, Shodex™ VC‐50 2D column
• Shimadzu ICPMS-2030: 1.20 kW RF power, He collision gas at 6 mL/min, sampling depth 5 mm

Main Results and Discussion

The method achieved baseline separation of Cr(III) (retention ≈ 7.8 min) and Cr(VI) (≈ 1.8 min) with detection limits of 0.20 µg/L and 0.35 µg/L, respectively. Calibration curves (2–10 µg/L) were linear (R² = 0.9999). Recoveries in fortified tap and well water ranged from 97% to 103%. Long‐term precision over 7 hours yielded RSDs < 2.6% for retention time and peak area.

Benefits and Practical Applications

• High sensitivity and low detection limits for regulatory compliance.
• Minimal sample preparation reduces contamination risk and labor time.
• Fast turnaround (< 10 min per run) supports high sample throughput in QA/QC labs.

Future Trends and Potential Applications

Advances may include on‐site portable IC-ICP‐MS systems for field screening, integration with automated sampling networks, and expanded speciation to other toxic metals. Regulatory changes on emerging contaminants (e.g., PFAS) could drive combined multi‐analyte platforms.

Conclusion

The IC-ICP-MS approach presented offers a robust, sensitive, and efficient solution for chromium speciation in drinking water. Its simplicity and reliability make it well‐suited for routine monitoring and compliance testing.