Intelligent Analysis of Wastewaters using an Agilent ICP-MS with Integrated Autodilutor

Importance of the Topic

The precise, reliable, and high-throughput analysis of wastewater is critical for environmental monitoring, regulatory compliance, and public health protection. Automating sample dilution and calibration preparation reduces analyst workload, minimizes human error, and accelerates sample turnaround in routine testing laboratories.

Study Objectives and Overview

This application note evaluates the performance of an integrated autodilution system (ADS 2) coupled to an Agilent 7900 ICP-MS for the analysis of 31 elements in wastewater. Key goals include demonstrating automatic calibration generation, reactive dilution of over-range samples, method detection limits, accuracy against certified reference materials, and long-term stability during extended runs.

Instrumentation Used

• Agilent 7900 ICP-MS with General Purpose plasma mode and ORS4 collision/reaction cell (He-KED)
• Agilent Advanced Dilution System (ADS 2) for automatic multipoint calibration and reactive dilution
• Integrated Advanced Valve System for ICP-MS (AVS MS) and SPS 4 autosampler
• Glass concentric nebulizer, quartz spray chamber, quartz torch, nickel-plated cones

Methodology

Stock standards containing 31 elements were prepared in 2% HNO₃/0.5% HCl and used by the ADS 2 to generate multipoint calibrations (2× to 200× dilutions). Two certified wastewater reference materials (ERM CA713 and CWW-TM-C) and a locally sourced wastewater sample were analyzed with minimal pretreatment (filtration). The ADS 2 performed automatic reactive dilutions when analyte signals exceeded calibration ranges. Internal standards were introduced online via the AVS MS system, and calibration verifications were run at regular intervals.

Main Results and Discussion

• Calibration linearity: R≥0.9995 for low-mass (Be) to high-mass (Pb) elements over the full range.
• Instrument detection limits: sub-ppt IDLs achieved (e.g., 0.0003 ppb for Cd, 0.0009 ppb for Hg).
• Calibration time: eight-level multipoint calibration fully automated in under 20 minutes from a single stock solution.
• CRM recoveries: 97–103% (ERM CA713) and 100–106% (CWW-TM-C) after reactive dilutions, within ±10% of certified values.
• Matrix spike recoveries: 85–110% for 15 elements, meeting EPA 6020B criteria of 100±25%.
• Long-term stability: CCV recoveries within ±10% and ISTD recoveries within ±20% over an eight-hour run.

Benefits and Practical Applications

• Fully automated preparation of multipoint calibrations from a single stock standard minimizes manual pipetting and contamination risk.
• Intelligent reactive autodilution handles unexpected high-concentration samples without operator intervention, improving lab efficiency.
• High matrix tolerance and collision cell technology enable accurate trace-element quantification in complex environmental samples.
• Online internal standard addition and integrated autosampler reduce sample carryover and ensure consistent precision.

Future Trends and Opportunities

• Integration of autodilution workflows with laboratory information management systems (LIMS) for seamless data handling.
• Expansion to additional sample types (soils, sediments, food) and further reduction of sample preparation steps.
• Increased use of machine learning for real-time data quality monitoring and predictive maintenance of instruments.
• Miniaturized and portable ICP-MS systems coupled with automated dilution for field-deployable environmental testing.

Conclusion

The Agilent 7900 ICP-MS equipped with the ADS 2 autodilution system reliably automates calibration, sample dilution, and quality control, delivering excellent sensitivity, accuracy, and stability for routine wastewater analysis. By reducing manual tasks and ensuring consistent performance over extended runs, laboratories can increase throughput, lower operating costs, and maintain data quality.

Reference

• Agilent Advanced Dilution System (ADS 2) – Technical overview, Agilent publication, 5994-7211EN
• US EPA Method 200.8: Trace Elements in Waters and Wastes by ICP-MS, Revision 5.4
• US EPA Method 6020B: Inductively Coupled Plasma-Mass Spectrometry, Revision 2