High Throughput, Multi-Element Analysis of Effluents by MP-AES

Significance of the Topic

Industrial, commercial, and agricultural activities generate effluents that may contain toxic elements such as As, Cd, Pb, and Hg. Effective monitoring of these metals is critical to protect soil and water resources, prevent bioaccumulation in aquatic organisms, and ensure compliance with national discharge regulations (CONAMA 430/2011 in Brazil). High-throughput and cost-effective analytical methods help laboratories maintain safety, reliability, and regulatory compliance.

Objectives and Study Overview

This application note evaluates a multi-element method for effluent analysis using the Agilent 4210 Microwave Plasma-Atomic Emission Spectrometer (MP-AES) equipped with an AVS 4 switching valve and SPS 4 autosampler. The goal is to demonstrate that this approach can reliably quantify 15 regulated elements in accordance with Brazilian environmental limits while improving lab productivity and reducing operating costs compared to traditional FAAS.

Methodology and Instrumentation

The study was structured into three analytical procedures:

• Procedure 1: Determination of Ag, B, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sn, and Zn by direct nebulization with multi-element calibration standards in 3% HNO₃ and cesium ionization buffer.
• Procedure 2: Determination of As and Se via hydride generation using MSIS accessory with NaBH₄ reductant and microwave-assisted pre-reduction.
• Procedure 3: Determination of Hg by cold vapor generation using SnCl₂ reductant and MSIS accessory.

Sample preparation involved filtration (0.45 µm) for dissolved Cu, Fe, and Mn, and microwave digestion of raw and filtered samples in HNO₃ or HCl matrices, followed by dilution to 3% acid concentration.

Instrumentation Used

• Agilent 4210 MP-AES with SPS 4 autosampler and AVS 4 switching valve
• OneNeb Series 2 nebulizer, double-pass glass cyclonic spray chamber, Easy-fit torch
• Multimode Sample Introduction System (MSIS) for hydride and cold vapor generation
• Agilent 5110 ICP-OES for independent accuracy validation

Main Results and Discussion

Calibration curves for all 15 elements exhibited excellent linearity (R > 0.999). Method limits of quantitation (MLOQs) were below Brazilian regulatory thresholds. Analysis of 10 industrial and domestic effluent samples showed most elements were below MLOQ, except boron in one sample (8.4 mg/L vs. 5.0 mg/L limit). Long-term stability testing over 8 hours yielded precision better than 1.5% RSD. Spike recovery tests on a representative sample produced recoveries within ±10% for all analytes. Comparison with ICP-OES confirmed accuracy for elements above MLOQ.

Benefits and Practical Applications of the Method

• Eliminates need for flammable or expensive gases by using nitrogen plasma
• Reduces operating costs with in-line nitrogen generation or tank supply
• Supports unattended, high-throughput operation with SPS 4 and AVS 4
• Offers robust plasma stability and low detection limits for hydride and cold vapor analyses
• Meets regulatory requirements for effluent monitoring, ideal for QA/QC and contract labs

Future Trends and Opportunities

Advances in automation and software (MP Expert quick read and dashboard tools) will further streamline method development by providing rapid scans of easily ionized elements (Na, K, Mg, Ca) to identify potential interferences. Integration of speciation techniques, expanded accessory options for other analyte classes, and cloud-based data management are expected to enhance laboratory efficiency and data quality in environmental monitoring.

Conclusion

The Agilent 4210 MP-AES combined with SPS 4 autosampler and AVS 4 switching valve provides a reliable, low-cost, and high-throughput solution for multi-element effluent analysis. It delivers regulatory compliance, excellent analytical performance, and significant cost savings compared to flame AAS, making it a valuable tool for environmental and industrial laboratories.

References

1. Sebastiani L., Scebba F., Tognetti R. Heavy metal accumulation and growth responses in Populus clones; Environmental and Experimental Botany, 2004, 52, 79–88.
2. Michalak A. Phenolic compounds and antioxidant activity in plants under heavy metal stress; Polish Journal of Environmental Studies, 2006, 15, 523–530.
3. Reza R., Singh G. Heavy metal contamination and its indexing for river water; International Journal of Environmental Science and Technology, 2010, 7, 785–792.
4. Mansour S.A., Sidky M.M. Heavy metals in water and fish from Fayoum Governorate, Egypt; Food Chemistry, 2002, 78, 15–22.
5. CONAMA Resolution 430/2011: Environmental effluent discharge limits, Brazilian Ministry of the Environment.
6. Sterritt R.M., Lester J.N. Atomic absorption spectrophotometric analysis of wastewater; Environmental Technology, 1980, 1(9), 402–417.
7. Cauduro J., Ryan A. Ultrafast ICP-OES determination of trace elements in water per EPA 200.7; Agilent Technologies, Application Note 5991-4821EN.
8. Proper W., Sugiyama N., Wilbur S. Use of qualifier ions to improve ICP-MS data quality for wastewater; Agilent Technologies, Application Note 5990-5890EN.
9. Agilent MP-AES Cost Savings Estimator; Agilent Technologies.
10. Agilent Flexible Sample Introduction with MSIS; Agilent Technologies, Application Note 5991-6453EN.
11. EPA Method 7196A: Hexavalent chromium by colorimetry; U.S. Environmental Protection Agency, 1992.
12. Agilent LC-ICP-MS method for Cr speciation in toys per EN71-3:2012; Agilent Technologies, Application Note 5991-2878EN.