High Throughput, Direct Analysis of Seawater using the Agilent 7800 ICP-MS with HMI for Aerosol Dilution

Significance of the Topic

Understanding trace metals such as Ni, Cu, Zn, Cd and Pb in seawater is essential for ensuring seafood safety and monitoring environmental health. High total dissolved solids (TDS) and complex matrix interferences in saline and estuarine waters pose analytical challenges, making robust, high-throughput methods valuable for regulatory and research laboratories.

Objectives and Study Overview

This study aimed to develop a direct analysis protocol for seawater and estuarine samples using the Agilent 7800 ICP-MS equipped with High Matrix Introduction (HMI) and ISIS 3 loop injection. The goal was to eliminate traditional sample preparation steps (matrix elimination, preconcentration, or dilution) while maintaining low detection limits and high sample throughput, and to compare performance against the existing Environment Agency (EA) method.

Methodology and Instrumentation

Instrumentation:

• Agilent 7800 ICP-MS with High Matrix Introduction (HMI)
• Agilent Integrated Sample Introduction System (ISIS 3) loop injection
• Agilent SPS 4 autosampler
• Micromist concentric nebulizer, quartz spray chamber, and quartz torch with 2.5 mm injector
• Octopole Reaction System (ORS4) in helium collision mode
• Online internal standards (Rh, Ir) and argon gas humidifier

Method Details:

• Aerosol-phase dilution in HMI reduces matrix loading, enabling direct introduction of high-TDS samples.
• ISIS 3 injects discrete 300 µL sample loops into a continuous carrier stream, achieving ~60 s sample-to-sample cycle times, including rinse steps.
• He collision mode with kinetic energy discrimination removes common polyatomic interferences without element-specific tuning.
• Calibration carried out in matrix-matched seawater; seawater blanks interspersed to calculate method detection limits (MDLs).

Main Results and Discussion

Detection limits (DLs) and MDLs were well below regulatory reporting levels (e.g., MDLs of 0.036 µg/L for Ni and 0.011 µg/L for Cd). Multiple seawater matrices—including interlaboratory test samples, EA QA samples, natural and spiked seawaters—were analyzed in random order. Results matched expected or assigned values and EA Starcross laboratory data within ±5%. Spike recoveries ranged from 98% to 105%. Internal standard signals remained stable within ±20%, demonstrating minimal matrix suppression and robust plasma performance. A batch of 45 samples was completed in 47 minutes.

Benefits and Practical Applications

By eliminating time-consuming sample preparation steps, the method reduces reagent costs, labor requirements, and contamination risk. Rapid, direct analysis supports high-throughput environmental monitoring, QA/QC in aquaculture and drinking water protection, and seafood safety testing without compromising data quality.

Future Trends and Possibilities

Future developments may include integrating advanced aerosol dilution with multi-mode reaction cells to handle even higher TDS levels, further automation of loop injection workflows, and application of AI-driven autotuning and data analytics for enhanced method optimization and long-term performance tracking.

Conclusion

The Agilent 7800 ICP-MS with HMI and ISIS 3 provides a fast, reliable direct analysis method for high-matrix seawater samples. It achieves low detection limits, stable performance, and high throughput without complex sample preparation, meeting stringent requirements for environmental and seafood safety monitoring.