Analysis of Blood Serum on the Liberty Series II ICP OES with the Axially- Viewed Plasma

Significance of the topic

The precise measurement of major, minor and trace elements in blood serum is fundamental for clinical diagnostics, nutritional studies and toxicology. Reliable quantification of electrolytes and trace metals supports disease diagnosis, patient monitoring and research on element-related pathologies. Rapid, multi-element analysis techniques that handle complex biological matrices with minimal sample preparation are in high demand across medical and industrial laboratories.

Objectives and study overview

This application note evaluates the performance of the Agilent Liberty Series II axially-viewed ICP-OES for direct analysis of blood serum. Key goals include:

• Establishing a single-run method to measure major (Na, K, Ca, Mg), minor (P, S) and trace elements (Cu, Fe, Zn, Al, Mn).
• Assessing ionization interference from easily ionized elements (EIE) such as Na, K and Ca.
• Demonstrating the use of cesium as an ionization buffer to improve calibration linearity.
• Validating accuracy against certified reference material (Seronorm Trace Elements Serum).

Methodology and instrumentation

Samples were prepared by reconstituting lyophilized serum and diluting at factors of 5, 20 and 100 in 1% HNO3 with 0.01% Triton X-100. Scandium (0.5 mg/L) served as an internal standard to correct viscosity and partial ionization effects. Cesium chloride (2% w/v Cs) was introduced online via a three-channel pump to saturate the plasma and minimize ionization interference.

An Agilent Liberty Series II ICP-OES with a 0.75 m Czerny-Turner monochromator was used under the following conditions:

• RF power: 1.0 kW, plasma gas 15 L/min, auxiliary gas 1.5 L/min
• Microconcentric nebulizer at 400 µL/min, nebulizer pressure 300 kPa
• Integration times: 3 s for most elements, 5 s for Al and Mn
• Polynomial background correction and up to 4 replicate measurements

Main results and discussion

Without cesium addition, atomic lines of EIEs (Na 330.237 nm, K 766.490 nm, Ca 422.673 nm) exhibited significant upward curvature due to ionization enhancement, failing calibration criteria. Cesium buffering restored linearity across all analyte lines, allowing a unified calibration.

Analysis of Seronorm serum yielded results within ±5% of certified values for all elements when cesium was used. Minor residual interference on Na at high concentration suggested a minimum dilution factor of 100 for accurate sodium determination. Long-term drift tests over one hour showed <1% RSD for major and trace analytes, confirming stable performance. The microconcentric nebulizer demonstrated reliable operation with no blockages and adequate sensitivity (~50% that of a standard concentric nebulizer) at 160 µL/min uptake.

Benefits and practical applications

• Single-run multi-element screening of serum saves time and reduces reagent use.
• Cesium buffering eliminates extensive matrix matching, simplifying standard preparation.
• Low sample consumption suits clinical settings where sample volume is limited.
• High throughput analysis supports routine QA/QC in hospitals, research and pharmaceutical labs.

Future trends and opportunities

Advances in plasma interface design and collision/reaction cell technologies are expected to further reduce matrix interferences. Integration with automated sample introduction and robotic workflows will streamline clinical testing. Emerging applications include real-time monitoring of trace element profiles in patient care and integration with data‐driven diagnostics using AI algorithms.

Conclusion

This study demonstrates that axially-viewed ICP-OES with cesium buffering and an internal standard can accurately measure a broad range of serum elements in a single analysis. The method offers rapid turnaround, low sample consumption and robust interference control, meeting the needs of clinical and industrial laboratories.

Instrumentation used

• Agilent Liberty Series II ICP-OES with axially-viewed plasma
• High-flow microconcentric nebulizer (Glass Expansion) at 400 µL/min
• Digital control via DEC Venturis computer and Agilent Plasma 96 software

Reference

1. Dubuisson C., Poussel E., Mermet J-M. J Anal At Spectrom. 1997;12:281–286.
2. Brenner I.B., Zander A., Cole M., Wiseman A. J Anal At Spectrom. 1997;12:897–906.
3. Ryan A. Agilent Appl. Note ICPES-21. 2010.
4. Sommer M.J., Rutman M.G., Wask-Rotter E., Wagoner H., Fritsche E.T. Agilent Appl. Note AA117. 2010.