Overcome unexpected interferences and accelerate environmental analysis using triple quadrupole ICP-MS

Importance of the Topic

Environmental monitoring of trace elements such as arsenic, cadmium, mercury and lead in water, soils and sediments is essential for safeguarding ecosystems and public health. Regulatory bodies demand highly sensitive, reliable methods with robust interference removal and high throughput to meet compliance and support routine analysis.

Objectives and Study Overview

This application note evaluates the advantages of triple quadrupole inductively coupled plasma mass spectrometry (TQ-ICP-MS) over conventional single quadrupole systems for environmental matrices. It compares interference removal efficacy, measurement accuracy and sample throughput when using helium collision mode (KED), single-mode reactive gases, and TQ-ICP-MS with oxygen as reaction gas.

Methodology

Samples of waters, wastewaters, sludges and seawater analogues were analyzed on a Thermo Scientific iCAP TQe ICP-MS. Daily performance checks and autotuning ensured instrument stability. Analytical modes compared were:

• Single quadrupole with He collision (KED)
• Single quadrupole with He and H₂
• Triple quadrupole in single TQ-O₂ mode
• Custom methods via Reaction Finder in Qtegra ISDS software

Used Instrumentation

Thermo Scientific iCAP TQe ICP-MS configured with:

• Glass MicroMist nebulizer, 400 µL/min
• Cyclonic quartz spray chamber at 3 °C
• Ni sampler and skimmer cones
• Forward power: 1,550 W; nebulizer gas: 1.00 mL/min
• O₂ reaction gas: 0.34–0.8 mL/min
  
• He collision gas: 4.3 mL/min with 3 V KED

Main Results and Discussion

Interference removal performance was assessed for arsenic and mercury in challenging matrices:

• Arsenic: Single quadrupole KED and SQ-O₂ showed biases up to 0.2 µg/L in calcium- or rare earth–rich samples. TQ-O₂ eliminated Cl-based and doubly charged interferences, delivering accurate As quantitation.
• Mercury: Tungsten oxides produced false positives up to 1.5 µg/L in SQ modes even at low W levels (5–50 µg/L). TQ-O₂ fully suppressed WO₂+ interferences, restoring correct Hg baselines.
• Throughput: A 29-element suite in single TQ-O₂ mode reduced per-sample acquisition time by >10% compared to dual-gas single quadrupole methods, translating to ~50 min time savings over 100 samples.

Benefits and Practical Applications

The TQ-ICP-MS approach with a single reactive gas mode:

• Ensures complete removal of polyatomic and doubly charged interferences across the full mass range.
• Delivers high confidence and compliance for regulated trace element testing.
• Improves laboratory throughput without extra gas-exchange cycles.
• Requires minimal additional infrastructure beyond standard collision/reaction gases.

Future Trends and Applications

Advancements may include automated reaction gas switching, expanded reaction gas chemistries for novel analytes, and integration with real-time data analytics. Coupling TQ-ICP-MS with automated dilution and online sample preparation will further streamline high-throughput environmental and industrial analyses.

Conclusion

This study demonstrates that triple quadrupole ICP-MS operated in single TQ-O₂ mode outperforms conventional single quadrupole methods in interference removal and throughput. It offers robust, accurate detection of trace contaminants in complex matrices, minimizing false positives and enhancing laboratory efficiency.

Reference

• Surekar B., Kutscher D. Overcome unexpected interferences and accelerate environmental analysis using triple quadrupole ICP-MS. Thermo Fisher Scientific Application Note 44484, 2021.
• Thermo Fisher Scientific. Sample preparation techniques for AAS, ICP-OES and ICP-MS in regulated testing laboratories. Technical Note 44483, 2020.
• Thermo Fisher Scientific. Direct analysis of trace elements in estuarine waters using triple quadrupole ICP-MS. Application Note 44417, 2020.