WCPS: Elemental Analysis of Brine Samples used for Lithium Extraction

Significance of the Topic

The rapid expansion of the Li-ion battery market has driven an urgent need for reliable, high-throughput analysis of lithium-rich brines. Brine extraction offers a cost-effective source of lithium compared to hard-rock mining, but its high total dissolved solids (TDS) and complex matrices pose analytical challenges. Accurate quantification of trace and major elements in these brines is critical for process optimization, quality control, and resource evaluation in battery-grade lithium production.

Objectives and Study Overview

This study aimed to develop and validate a robust inductively coupled plasma optical emission spectrometry (ICP-OES) method for the simultaneous determination of B, Ca, Li, Mg, Mn, Si, K, and Sr in high-TDS brine samples (15–25% NaCl). Key goals included:

• Demonstrating long-term stability and precision over extended analysis sequences.
• Establishing method detection limits (MDLs) and spike recovery performance in real brine matrices.
• Evaluating the effectiveness of inline internal standardization and advanced instrument features to mitigate matrix interferences and maintenance burdens.

Methodology and Instrumentation

Sample Preparation and Calibration

• Brine samples were gravimetrically diluted at 1:20 and 1:100 in 5% HNO₃ to achieve a final TDS of ~1%.
• A multielement internal standard (Sc, In, Rb) was introduced inline via a seven-port switching valve to correct physical and ionization interferences.
• Calibration employed both matrix-matched standards and the MultiCal function to extend the linear dynamic range for elements present from ppb to percentage levels.

Instrument Configuration

• An Agilent 5800 VDV ICP-OES with a SeaSpray nebulizer, double-pass cyclonic spray chamber, and 1.8 mm demountable injector torch.
• Advanced Valve System (AVS 7) switching valve to minimize exposure of the plasma torch to high-salt particulates and reduce carryover.
• Radial viewing mode selected to lower easily ionized element effects from NaCl matrices.
• Key operating parameters: RF power 1.45 kW, plasma flow 13.5 L/min, auxiliary flow 1.6 L/min, nebulizer flow 0.7 L/min, replicate read time 3×5 s.

Used Instrumentation

• Agilent 5800 Vertical Dual View ICP-OES
• AVS 7 Advanced Valve Switching System
• SeaSpray nebulizer and cyclonic spray chamber
• Demountable injector torch (1.8 mm I.D.)
• SPS 4 autosampler
• ICP Expert software with IntelliQuant Screening, MultiCal, and Early Maintenance Feedback (EMF)

Key Results and Discussion

Method Detection Limits and Stability

• MDLs for target elements ranged from 0.0006 to 0.129 mg/L in a 1% NaCl matrix, meeting routine analytical requirements.
• Over 360 consecutive sample measurements in a 10-hour run, recoveries remained within ±3% with no QC failures, demonstrating excellent long-term stability.

Accuracy and Precision

• Spike recovery in real brine at 1 ppm yielded 91–105% recoveries for B, Li, Mg, Mn, Si, and Sr.
• Quantification at two dilution levels (1:20, 1:100) across three brines showed relative percentage differences below 7.4% for all elements.

Instrument Features Enhancing Performance

• MultiCal extended the linear dynamic range, reducing the need for multiple dilutions and remeasurements.
• IntelliQuant Screening provided rapid semiquantitative profiles to optimize calibration ranges and sample dilutions.
• EMF diagnostics minimized unplanned downtime by indicating maintenance requirements only when necessary.

Benefits and Practical Applications

• Robust handling of high-TDS, heterogeneous brine matrices with minimal matrix matching.
• High sample throughput with stable performance over extended sequences.
• Wide dynamic range enabling simultaneous trace and major element determination.
• Reduced maintenance and consumable costs through AVS valve switching and EMF feedback.
• Improved confidence in QA/QC workflows for battery-grade lithium production.

Future Trends and Applications

• Integration of real-time, inline ICP-OES monitoring for continuous brine processing control.
• Expansion to multianalyte speciation studies coupling ICP-OES with chromatography or laser ablation.
• Advanced data analytics and machine learning for predictive maintenance and process optimization.
• Application of similar methodologies to other critical battery metals (e.g., cobalt, nickel) in complex matrices.

Conclusion

The developed ICP-OES method using the Agilent 5800 VDV with AVS 7 demonstrates high accuracy, precision, and stability for multielement analysis of lithium brine samples. Inline internal standards, advanced software tools, and optimized hardware configurations streamline workflow, minimize maintenance, and ensure reliable results for industrial and research applications in lithium extraction.

References

1. Xu C, Dai Q, Gaines L, et al. Future material demand for automotive lithium-based batteries. Commun Mater. 1:99 (2020).
2. Agilent Technologies Inc. Reduce Costs and Boost Productivity with the Advanced Valve System (AVS) 6 or 7 Port Switching Valve System. Publication 5991-6863EN.
3. Agilent Technologies Inc. Agilent IntelliQuant Screening: Smarter and quicker semiquantitative ICP-OES analysis. Publication 5994-1518EN.
4. Agilent Technologies Inc. Quantification of Key Elements in Lithium Brines by ICP-OES. Publication 5994-4868EN.