Sensitive determinations of hexavalent chromium in drinking water using a compact IC system

Importance of the Topic

Hexavalent chromium is a potent oxidizing form of chromium with significant toxicity and carcinogenic potential. Its presence in drinking water is strictly regulated at low ng/L levels to protect human health and meet environmental compliance.

Objectives and Study Overview

This study evaluates a compact Dionex Inuvion ion chromatography system for sensitive detection of Cr(VI) in potable water following modified US EPA methods 218.6/218.7. The aim is to demonstrate quantification down to 10 ng/L in municipal and synthetic high ionic strength samples.

Methodology and Sample Preparation

Samples include municipal drinking water and a synthetic High Ionic Water (HIW) matrix containing representative anions and fluoride. A sample adjustment buffer is added before injection. Calibration uses seven concentration levels from 0.01 to 0.20 µg/L with seven replicates at the lowest level to establish the method detection limit (MDL).

Used Instrumentation

• Dionex Inuvion IC system with column heater and pump degas module
• Dionex IonPac AS7, 2 mm column
• Dionex AS-DV autosampler with 5 mL vials
• Thermo Scientific AXP-MS auxiliary pump for post-column reagent delivery
• ICS-Series VWD or UltiMate 3000 DAD detector at 530 nm

Results and Discussion

The calibration curve showed excellent linearity (r² = 0.9989). The MDL was determined as 5.6 ng/L, matching EPA Method 218.7 specifications. Chromatograms demonstrated well-resolved Cr(VI) peaks in standards, HIW matrix, spiked samples (99.5% recovery at 0.1 µg/L), and municipal water.

Benefits and Practical Applications

The compact IC setup provides high sensitivity, reproducibility, and straightforward operation for routine monitoring of Cr(VI) in drinking water. It supports environmental laboratories in QA/QC workflows and regulatory compliance testing.

Future Trends and Potential Applications

Emerging developments include automated inline sample cleanup, further system miniaturization, coupling with mass spectrometry for speciation analysis, and deployment of greener reagents. Real-time field sensors for continuous Cr(VI) monitoring may also gain traction.

Conclusion

The Thermo Scientific Dionex Inuvion IC system enables reliable quantification of trace hexavalent chromium in diverse water matrices at levels below regulatory limits, confirming its suitability for environmental and drinking water analysis.

Reference

1. U.S. EPA Method 218.6 and 218.7
2. Thermo Scientific Application Update 179
3. Thermo Scientific VWD and DAD detector manuals