Direct, Rapid Analysis of Undiluted Seawater using ICP-MS with an Aerosol Dilution System

Importance of the topic

The analysis of trace metals in seawater is critical for environmental monitoring, marine ecology, and compliance with regulatory standards. Achieving reliable measurements at µg/L to ng/L levels is challenging due to high total dissolved solids (2–3.5% TDS), which exceed typical ICP-MS tolerance by 10–20×.

Objectives and Article Overview

This study evaluates direct, rapid analysis of undiluted seawater using an ICP-MS with aerosol dilution (HMI) and loop injection (ISIS3). The goal was to simplify sample preparation, minimize contamination, and maintain high throughput while achieving low detection limits for Ni, Cu, Zn, Cd, and Pb.

Methodology and Used Instrumentation

The work employs an Agilent 7800 ICP-MS equipped with High Matrix Introduction (HMI) and an Integrated Sample Introduction System (ISIS3). Key parameters included:

• 300 µL loop injection, Micromist nebulizer, quartz spray chamber, 2.5 mm injector torch
• Internal standards Rh and Ir added online at 1:1 ratio
• Helium collision mode to mitigate spectral interferences
• Operating conditions: 1600 W forward power; carrier gas ~0.68 L/min; dilution gas ~0.27 L/min; He cell gas 5.0 mL/min; 5 V energy discrimination

Main Results and Discussion

Various seawater matrices (Quasimeme estuarine/open ocean, EA AQC, natural and spiked samples) were analysed. Calibration and method detection limits (MDLs) in the seawater matrix were:

• Ni: DL 0.013 µg/L; MDL 0.036 µg/L
• Cu: DL 0.0096 µg/L; MDL 0.055 µg/L
• Zn: DL 0.049 µg/L; MDL 0.22 µg/L
• Cd: DL 0.0038 µg/L; MDL 0.011 µg/L
• Pb: DL 0.013 µg/L; MDL 0.022 µg/L

Replicate measurements (n=4) showed recoveries within 99–105%, and internal standard drift was minimal throughout the run, demonstrating excellent matrix tolerance.

Benefits and Practical Applications of the Method

• Direct analysis of undiluted seawater without complex pretreatment
• Reduced contamination risk by eliminating extraction or dilution reagents
• High throughput with sample-to-sample times of ~60 s
• Sub-ppb MDLs suitable for trace and ultratrace monitoring

Future Trends and Potential Uses

Extending aerosol dilution and loop injection to matrices such as industrial effluents, brines, and biofluids is anticipated. Integration with high-resolution or tandem MS could enhance selectivity. Automated, in-situ monitoring platforms may leverage this approach for real-time environmental surveillance.

Conclusion

The Agilent 7800 ICP-MS with HMI and ISIS3 provides a fast, robust method for direct trace metal analysis in undiluted seawater, combining low detection limits with streamlined workflows for environmental and industrial applications.

Reference

No formal literature references were provided in the original text.