Accurate Analysis of Factory Effluents using ICP-MS with Aerosol Dilution

Significance of the Topic

Industrial wastewater represents a complex mixture of dissolved salts, metals, and organic components. Accurate multielement analysis of factory effluents is critical for environmental compliance, process optimization, and public health protection. High-matrix samples pose analytical challenges such as plasma instability, matrix suppression, and polyatomic interferences. Advances in inductively coupled plasma mass spectrometry (ICP-MS) with automated aerosol dilution offer a streamlined and robust solution for routine monitoring of trade effluents.

Objectives and Study Overview

This work evaluates the performance of the Agilent 7850 ICP-MS equipped with an Ultra High Matrix Introduction (UHMI) system and Octopole Reaction System (ORS4) for the simultaneous determination of 32 elements in factory wastewater. Key goals include:

• Assessing the effectiveness of UHMI aerosol dilution (UHMI-8) to handle high total dissolved solids without manual dilution.
• Characterizing detection limits, calibration linearity, and accuracy using certified reference materials (CRMs) and spiked matrices.
• Demonstrating long-term stability and interference control under Helium, enhanced Helium (HEHe), and Hydrogen modes.

Methodology and Instrumentation

Factory effluent samples were collected from five industrial sites: a university, PCB plating facility, chemical plant, rubber manufacturer, and metal finishing company. Samples were digested per JIS K 0102 and spiked with up to 100 000 mg/L of major matrix elements (Na, Mg, K, Ca). An Agilent 7850 ICP-MS with UHMI and ORS4 collision/reaction cell was operated under the following conditions:

• Sample introduction: MicroMist concentric nebulizer, temperature-controlled quartz spray chamber, quartz torch.
• UHMI aerosol dilution: automated Ar gas addition (UHMI-8).
• ORS4 modes: He kinetic energy discrimination for routine interferences; HEHe for high-energy collisions; H₂ mode for specific analytes (Ca, Fe, Se).
• Calibration: five- or six-point curves in 4 % HNO₃ + 0.5 % HCl; online internal standards (⁶Li, Sc, Ge, Y, Rh, In, Te, Tb, Lu, Ir).

Main Results and Discussion

The ICP-MS exhibited excellent sensitivity and linearity (R² ≥ 0.9998) across major (Na, K) and trace analytes (As, Hg). Detection limits ranged from sub-ppt to low ppb. Key findings include:

• CRM analysis: recoveries for 32 elements in low-matrix and high-matrix CRMs were within 90–105 % of certified values.
• Spike recovery in real wastewater: most elements recovered within ±10 % at 100 ppb and 100 000 ppm matrix levels.
• Interference control: ORS4 in He mode effectively removed common Ar-, Ca-, and Cl-based polyatomics. H₂ mode eliminated ⁴⁰Ar interference on ⁴⁰Ca, avoiding ⁸⁸Sr²⁺ overlap on ⁴⁴Ca.
• Long-term stability: over 16 h and 160 injections, internal standard recoveries remained within 70–115 % (JIS K0102 QC limit 60–125 %). Continuing calibration verification (CCV) recoveries stayed within ±10 %.
• IntelliQuant semiquantitative profiling provided a rapid heat‐map of up to 78 elements, revealing unexpected metallic contaminants (e.g., Au in PCB effluent).

Benefits and Practical Applications

The Agilent 7850 ICP-MS with UHMI offers significant advantages for industrial effluent monitoring:

• Elimination of manual liquid dilution steps reduces handling errors and contamination risk.
• One-run, wide dynamic range analysis (10 orders of magnitude) covers major and trace elements simultaneously.
• Automated plasma and cell tuning via preset methods accelerates method development.
• Robust aerosol dilution ensures stable performance for high-matrix samples without frequent maintenance.
• Comprehensive semiquantitative screening identifies non-regulated and unexpected elements.

Future Trends and Applications

Ongoing and emerging directions include:

• Integration of advanced reaction gases or mixed-gas cell modes for even lower detection limits and interference removal.
• Coupling with on-line sample preparation (e.g., microflow digestion) for fully automated workflows.
• Application of machine learning to semiquantitative data sets for anomaly detection and process diagnostics.
• Expanded use in compliance monitoring under evolving environmental regulations and emerging contaminants.
• Remote operation and cloud-based data management for decentralized water quality networks.

Conclusion

This study demonstrates that the Agilent 7850 ICP-MS with UHMI aerosol dilution and ORS4 collision/reaction cell delivers high sensitivity, accuracy, and long-term stability for multielement analysis of factory effluents. The approach accommodates high matrix loads without manual dilution, meets stringent QC criteria, and streamlines routine laboratory workflows. Its combination of robustness and dynamic range makes it a powerful tool for environmental compliance and industrial process control.

Reference

• U.S. EPA Method 200.7: Determination of Metals and Trace Elements in Water and Wastes by ICP-OES, Revision 4.4, 1994.
• U.S. EPA Method 200.8: Determination of Trace Elements in Waters and Wastes by ICP-MS, Revision 5.4, 1994.
• U.S. EPA SW-846 Test Method 6020B: Inductively Coupled Plasma – Mass Spectrometry, Revision 2, 1994.
• Agilent Technologies: Ultra High Matrix Introduction (UHMI) ICP-MS Technology Brief, Publication 5994-1170EN.
• Agilent Technologies: Enhanced Helium Collision Mode with ORS4 Cell, Publication 5994-1171EN.
• JIS K 0102: Testing Methods for Industrial Wastewater – Japanese Industrial Standard.