Rapid and Reliable Routine Analysis of Urine by Octopole Reaction Cell ICP-MS

Significance of the Topic

Monitoring elemental concentrations in urine provides a non-invasive assessment of both essential nutrients (such as Se, Mo, Co, Cu, Zn) and toxic or carcinogenic metals (for example, Be, Pb, Cd, U). Accurate multi-element analysis supports clinical diagnostics, occupational exposure screening and environmental health studies by revealing imbalances or contaminant uptake that can guide therapeutic interventions and regulatory measures.

Objectives and Study Overview

This study aims to develop, validate and demonstrate a rapid, reliable routine method for simultaneous determination of 23 trace elements in human urine using octopole reaction cell ICP-MS. Key goals include:

• Minimizing sample preparation time through a simple acid dilution protocol.
• Evaluating instrumental performance in terms of sensitivity, stability and interference removal.
• Assessing method precision, accuracy and long-term robustness with reference materials and population samples.

Methodology and Instrumentation

A one-step sample preparation involves mixing 1 mL urine with 4 mL 1% (v/v) nitric acid containing 5 µg/L terbium internal standard. Calibration employed standard additions over a concentration range tailored to each analyte. Data acquisition used an Agilent 7500c ICP-MS equipped with an octopole reaction system (ORS) to eliminate polyatomic interferences. Key operating parameters included a Babington nebulizer, Scott-type double-pass spray chamber, plasma power of 1.5 kW and optimized helium or hydrogen gas flows for collision/reaction cell cleaning.

Instrumentation

The Agilent 7500c ICP-MS features:

• An octopole reaction cell pressurized with helium or hydrogen to remove argon- and matrix-based spectral overlaps.
• Autotunable lens and gas controls via ChemStation software, enabling reproducible “target-tuning” without extensive user intervention.
• A wide-bore (2.5 mm ID) torch injector for enhanced tolerance to complex matrices.

Key Results and Discussion

Limits of detection in undiluted urine ranged from 0.4 ng/L (238U) to 143 ng/L (78Se), well below physiological concentrations of essential elements. Short-term repeatability RSDs were 0.6–3.0%, and long-term stability over 5 hours yielded RSDs of 2.5–6.2%. No nebulizer clogging or injector fouling was observed during 12 hours of continuous operation. Helium collision mode effectively removed interferences for Cr, As, V and others, while hydrogen reaction gas optimized selenium analysis by suppressing Ar2+ species. Method accuracy and precision were confirmed through analysis of multiple certified urine reference materials (Lyphochek®, Clinchek®, Medisafe™) and pooled control samples, with measured values agreeing with certified ranges within acceptable limits. A survey of 63 urine specimens from the general population produced element concentration distributions consistent with published national biomonitoring data.

Benefits and Practical Applications

• High throughput: a single analyst can prepare and analyze over 100 samples per hour.
• Minimal sample preparation reduces contamination risk and labor costs.
• Multi-element screening in a single run streamlines clinical workflows for toxicology, nutrition assessment and occupational health.
• Robust interference removal ensures reliable data across varying urine matrices without complex mathematical corrections.

Future Trends and Opportunities

Advancements may include integration of automated sample handling to further increase throughput, adoption of triple quadrupole ICP-MS for enhanced interference control and expansion into speciation analysis of metal complexes. Combining high-resolution mass spectrometry with data-driven interpretive tools could support personalized exposure profiling and predictive health risk assessment.

Conclusion

The validated octopole reaction cell ICP-MS approach enables efficient, accurate and robust multi-element urine analysis. Its simple dilution-acidification protocol, combined with ORS interference removal and automated tuning, meets demanding clinical and environmental monitoring requirements. This method provides a practical platform for routine biomonitoring, occupational exposure assessment and research applications.

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