Managing the challenges of analyzing brine solutions of variable concentration using inductively coupled plasma mass spectrometry (ICP-MS) equipped with argon gas dilution

Summary of Argon Gas Dilution ICP-MS Analysis of Brine Solutions

Significance of Topic

Brine solutions containing up to 25 percent w w sodium chloride are encountered in environmental monitoring industrial processes and lithium extraction from underground reservoirs. Reliable quantification of trace metals and impurities including rare earth elements in these high salt matrices is essential for quality control environmental assessment and resource recovery.

Goals and Overview

The study aimed to demonstrate high sensitivity accuracy and robustness when analyzing concentrated brine samples by coupling an iCAP RQplus ICP MS with automated argon gas dilution. The method avoids manual liquid dilution and tackles matrix induced signal suppression and instrument maintenance challenges.

Methodology and Instrumentation

The analytical workflow was based on an iCAP RQplus single quadrupole ICP MS fitted with an argon gas dilution module. Key configuration and operating parameters included ultraclean PFA microflow nebulizer quartz cyclonic spray chamber cooled at 2.7 degrees C quartz torch with a 2.5 mm injector kinetic energy discrimination with helium collision gas and optimized gas flows to achieve high dilution. An internal standard mixture of Sc Y Rh Te and Lu was added online. Calibration standards and quality control solutions were prepared in mixed acid diluent and spikes performed at relevant concentration levels. Data acquisition and instrument health monitoring were managed through Qtegra Intelligent Scientific Data Solution software.

Main Results and Discussion

Method detection limits ranged from sub microgram per liter for rare earth elements to low microgram per liter for common metals with linear calibration coefficients above 0.998. Internal standard recoveries remained stable between 78 and 122 percent across brine matrices from 0.5 to 4 percent w w with spike recoveries for 34 analytes within 80 to 120 percent and relative standard deviations below 7 percent. The highest dilution setting permitted direct aspiration of up to 25 percent w w brine with acceptable internal standard recoveries and controlled signal suppression. Long term testing over nine hours and 120 brine samples demonstrated robust performance with consistent QC and spike recovery results. Post analysis inspection confirmed that argon dilution significantly reduced deposition on cones compared to undiluted aspiration.

Benefits and Practical Applications

• Eliminates time consuming manual dilution steps and maximizes sample throughput
• Reduces matrix induced signal suppression and detector overload risks
• Maintains instrument uptime by minimizing cone and nebulizer fouling
• Delivers accurate quantification of trace elements including lithium common impurities and rare earth elements in high salt matrices

Future Trends and Opportunities

Advances may include integration of real time sample dilution control feedback enhanced collision cell chemistries for improved interference removal and application of this approach to other challenging matrices such as geothermal waters produced fluids and high salinity waste streams. Coupling with high resolution or tandem mass spectrometry could further extend analytical capabilities for isotope ratio studies and speciation.

Conclusion

The optimized argon gas dilution method on the iCAP RQplus ICP MS provides a robust high throughput solution for elemental analysis of concentrated brine samples. It achieves low detection limits wide linear ranges stable internal standard recovery and minimal maintenance requirements enabling accurate and reliable monitoring of critical elements in demanding matrices.

References

1 Thermo Fisher Scientific Application note on lithium and impurity analysis in brine by ICP OES
2 Thermo Fisher Scientific Application note on composition of lithium rich minerals by ICP OES
3 Reisman Weber Rare Earth Elements review of production processing recycling and environmental issues US EPA
4 Abbott Haley McManus Reimers Sedimentary flux of dissolved rare earth elements to the ocean
5 Thermo Fisher Scientific Technical note on argon gas dilution with iCAP RQ ICP MS