Determination of 23 Nutritional, Essential and Toxic Elements in Urine by ICP-MS Using Alkaline Dilution

Importance of the Topic

Analysis of nutritional, essential, and toxic elements in urine is vital for monitoring human health, detecting environmental exposures, and assessing metabolic status. Urine offers a noninvasive matrix reflecting trace element excretion, and inductively coupled plasma mass spectrometry (ICP-MS) provides the sensitivity and precision required for ultra-trace quantification.

Objectives and Study Overview

This work presents a validated method using the Shimadzu ICPMS-2050 LF system to determine 23 elements in urine samples. Key aims include simplifying sample preparation, ensuring stable analysis of volatile species, minimizing carry-over, and achieving high throughput with robust quality control.

Methodology and Instrumentation

Sample preparation and calibration

• Ten-fold alkaline dilution of urine using a mixture of ammonia, Triton X-100, EDTA, and isopropanol to prevent protein denaturation, stabilize iodine, and improve mercury washout.
• Matrix-matched calibration with ClinCal 9988 urine calibrator at five levels (0–100% concentration) and supplementary matrix-free calibration for mercury.
• Quality control using ClinCheck and Seronorm urine reference materials at the beginning and end of each batch.

Interference removal and automation

• Collision/reaction cell applying helium or hydrogen to eliminate spectral overlaps for selected isotopes.
• LabSolutions ICPMS software features such as Extended Rinsing and automated QC and internal standard recovery monitoring.

Used Instrumentation

• Shimadzu ICPMS-2050 LF with collision/reaction cell
• AS-20 round-table autosampler with dual rinse and low-dead-volume spacer
• Cyclonic Twister spray chamber at 5 °C and coaxial nebulizer (0.4 ml/min)
• Mini-Torch with nickel sampling and skimmer cones
• Gas flows: Ar plasma (9.0 L/min), auxiliary Ar (1.1 L/min), carrier Ar (0.85 L/min), He (6.0 mL/min), H2 (7.0 mL/min)

Main Results and Discussion

Influence of sample matrix

• Matrix-matched and matrix-free calibration curves for mercury overlapped perfectly, confirming compensation for varying dissolved solids.

Memory effects and carry-over

• Alkaline media reduced mercury memory to below 0.1% after high-concentration samples.
• Extended rinsing triggered above 1.3× the highest calibration level further minimized carry-over.

Sensitivity, stability, and QC recovery

• Method quantification limits met or exceeded typical reference ranges for all 23 elements.
• Internal standard recoveries remained stable over ~70 samples, and QC reference materials were traced within specified limits.

Benefits and Practical Applications

• Rapid multi-element urine analysis with sample cycle times under three minutes.
• Safe determination of volatile elements such as iodine and mercury with minimal carry-over.
• High automation and throughput suitable for clinical diagnostics, occupational health, and environmental monitoring.

Future Trends and Opportunities

The alkaline dilution ICP-MS workflow can be adapted to other biological fluids and extended by chromatographic speciation for detailed profiling. Further developments in collision cell chemistries, fully automated sample preparation, and real-time data integration will enhance sensitivity, throughput, and applicability in personalized medicine and large-scale biomonitoring.

Conclusion

The Shimadzu ICPMS-2050 LF method with alkaline dilution delivers a robust, sensitive, and high-throughput solution for quantifying nutritional, essential, and toxic elements in urine. Its excellent precision, low memory effects, and broad dynamic range support reliable routine analysis in diverse laboratory settings.

Reference

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4. Medical Laboratory Bremen. Analyses information. Available at https://www.mlhb.de/analysen (Accessed 21 May 2025).