Resolving the challenges of analyzing samples with high and variable matrix content using Argon Gas Dilution (AGD) with ICP-MS

Importance of the topic

Analytical challenges arise when sample matrices exceed 0.2% m/v total dissolved solids in ICP-MS, leading to signal suppression, interface clogging and increased maintenance. Argon gas dilution (AGD) provides an online solution that preserves sensitivity and throughput without manual dilution.

Objectives and overview of the study

This work demonstrates how AGD implemented in Thermo Scientific iCAP RQ, TQe and TQ ICP-MS systems addresses high and variable matrix loads, enabling robust, direct analysis of environmental, food and industrial samples up to 25% TDS.

Methodology and instrumentation used

• AGD principle: additional argon flow via an internal mass flow controller dilutes aerosol inside the sample introduction while maintaining constant total gas flow.
• Key components: iCAP RQ, iCAP TQe and iCAP TQ ICP-MS; QCell collision/reaction cell (He KED or reactive gases); robust skimmer cone insert; V-groove nebulizer; Qtegra ISDS software autotune at 0.25–0.30 L/min nebulizer gas.
• Operating modes: single quadrupole KED and triple quadrupole with O2, H2 or NH3 reaction gases.

Main results and discussion

• Water analysis: direct measurement of drinking, surface and sea waters over 9 hours (171 samples) without manual dilution. Internal standard recoveries remained within 69–122%, even for undiluted sea water, ensuring accurate correction.
• Detection limits and spike recoveries for estuarine waters matched or exceeded those of liquid dilution, with fully removed interferences on elements such as As using SQ-KED and TQ-O2 modes.
• Food sample digests: 283 microwave-digested food samples analyzed over 14 hours with stable internal standard performance and compliance with QC recovery limits.
• Refined nickel: impurities in solutions containing 1,000–8,000 mg/L Ni were quantified with 80–120% recovery using AGD, avoiding upfront dilution and maintaining high sensitivity.
• High TDS matrices: with a V-groove nebulizer, samples up to 25% TDS were analyzed directly, showing 70–120% internal standard recovery over 4.5 hours and spike recoveries of 85–116%.

Benefits and practical applications

• Eliminates manual dilution steps, reducing contamination risk and labor.
• Improves plasma robustness and reduces cone deposition, lowering maintenance frequency.
• Maintains detection limits and sensitivity while extending matrix tolerance to high TDS samples.
• Enhances laboratory throughput for environmental monitoring, food safety and industrial QA/QC.

Future trends and applications

Further developments may include dynamic per-sample AGD control, hybrid integration with automated liquid dilution, expansion to complex industrial and mining matrices, and advanced interface designs to push matrix tolerance even higher.

Conclusion

Argon gas dilution integrated in modern ICP-MS platforms enables direct, robust and sensitive analysis of samples with TDS up to 25% without manual dilution. This approach preserves method detection limits, reduces maintenance and supports diverse analytical workflows across environmental, food and industrial applications.

References

• Technical Note 43202 Thermo Scientific Argon Gas Dilution with iCAP RQ ICP-MS
• Application Note 44417 Triple Quadrupole ICP-MS for Estuarine Waters
• Application Note 44495 Multi-element Determination in Surface and Sea Waters
• Application Note 44448 Direct Analysis of Environmental Samples Using AGD
• Application Note 44474 Trace Metals in Food with Triple Quadrupole ICP-MS
• Application Note 44463 Refined Nickel Analysis with Triple Quadrupole ICP-MS
• Application Brief 43327 Direct Analysis of 25% Sodium Chloride Matrix Using AGD