NEMC: Chromium Speciation of Drinking Waters by IC-ICPMS

Importance of the Topic

Understanding the distribution of chromium species in drinking water is essential because trivalent chromium (Cr(III)) is a necessary dietary element, while hexavalent chromium (Cr(VI)) is a known carcinogen and reproductive toxicant. Accurate speciation supports regulatory compliance, risk assessment and ensures public health protection.

Objectives and Study Overview

• Develop a rapid, sensitive method for simultaneous determination of Cr(III) and Cr(VI) in drinking and environmental waters using ion chromatography coupled to inductively coupled plasma mass spectrometry (IC-ICPMS).
• Optimize chromatographic and plasma conditions to achieve baseline separation and low detection limits without complex sample preparation.
• Demonstrate method accuracy, precision and stability through calibration, spiked recoveries and long-term injections.

Methodology

The method employs a single isocratic separation using 9 mM nitric acid as the mobile phase on a Shodex VC-50 2D column at 50 °C, flow rate 0.3 mL/min and 20 µL injection. Samples—tap water, well water, mixed standards and spiked matrices—are analyzed directly without derivatization or pre-treatment. Calibration curves for both species over 2–10 µg/L show linearity (R2=0.9999).

Used Instrumentation

• Shimadzu Prominence Ion Chromatograph with inert flow path.
• Shimadzu ICPMS-2030 with helium collision cell to remove polyatomic interferences, monitoring Cr at m/z 52.

Main Results and Discussion

Chromatographic separation achieves baseline resolution within 10 minutes, with retention times of 7.79 min for Cr(III) and 1.84 min for Cr(VI). Limits of detection are 0.20 µg/L (Cr(III)) and 0.35 µg/L (Cr(VI)); quantitation limits are 0.67 and 1.67 µg/L, respectively. Precision over seven hours yielded RSD of 0.34% (retention time Cr(III)) to 1.31% (retention time Cr(VI)) and 1.66% to 1.50% RSD for peak areas. Recovery studies in tap and well water show 97–103% for both species, indicating excellent accuracy in real matrices.

Benefits and Practical Applications

• No sample pretreatment avoids contamination and reduces labor.
• Use of dilute nitric acid mobile phase lowers background and matrix interferences.
• Fast analysis time and high throughput support routine monitoring in environmental and drinking water laboratories.
• High sensitivity and precision meet or exceed regulatory requirements for chromium speciation.

Future Trends and Potential Applications

Advances may include on-site portable IC-ICPMS platforms, further miniaturization, automated sample handling and real-time monitoring. Emerging hyphenated techniques and improved collision cell chemistries could lower detection limits and expand speciation to additional trace metal forms.

Conclusion

The developed IC-ICPMS method provides a robust, rapid and accurate tool for chromium speciation in water. Its minimal sample preparation, strong performance metrics and compatibility with regulatory frameworks make it suitable for routine QA/QC and research applications.

References

• Johnson S.E. et al. The contemporary anthropogenic chromium cycle. 2006.
• Agency for Toxic Substances and Disease Registry. Chromium: Standards and regulations.
• NIOSH. Hexavalent Chromium. 2023.