Measurement of Litium (Li) and Aluminium (Al) in Human Sera

Importance of the Topic

Lithium is a cornerstone in psychiatric treatment with a narrow therapeutic index requiring precise serum monitoring to avoid toxicity. Aluminium exposure poses risks in patients with renal impairment when administered parenterally, necessitating routine determination in biological fluids.

Study Objectives and Overview

This study details the quantification of lithium and aluminium in human serum reference materials (NIST 909b Levels I and II) using spectrophotometric atomic absorption techniques. Flame atomic absorption spectrometry (FAAS) assessed lithium, while graphite furnace atomic absorption spectrometry (GFAAS) employed the standard addition method for aluminium.

Methodology

• Lithium Analysis: Samples were prepared by mixing serum, cesium solution as ionization buffer, and hydrochloric acid, diluted to volume. Calibration curves up to 2.0 µg/mL exhibited excellent linearity (r=1.0000).
• Aluminium Analysis: Standard addition was applied to serum spiked with known Al concentrations, using Triton X-100 and nitric acid for matrix matching. A temperature program on a platform tube enabled atomization and matrix removal.

Used Instrumentation

• Atomic absorption spectrometer with flame (air-acetylene) attachment, 670.8 nm wavelength, 0.5 nm slit for Li.
• Graphite furnace module with platform tube, 309.3 nm wavelength, 0.5 nm slit, D2 background correction for Al.

Main Results and Discussion

• Lithium: Measured values of 4.20 µg/mL and 17.59 µg/mL closely matched certified concentrations of 4.265±0.0034 µg/mL and 18.04±0.016 µg/mL, confirming method accuracy.
• Aluminium: Determined concentrations were 34.2 ng/mL and 49.5 ng/mL for Levels I and II. Precision (%RSD) remained below 3% across standard additions, indicating reliable quantification despite lack of certified values.

Practical Benefits and Applications

Routine implementation of these AAS protocols supports clinical laboratories in monitoring patient therapy, ensuring dosage safety for lithium and detecting potential aluminium toxicity in vulnerable populations.

Future Trends and Opportunities

Advances may include coupling with inductively coupled plasma mass spectrometry (ICP-MS) for multi-element analysis, automation of sample preparation, and enhanced sensitivity using novel atomization techniques.

Conclusion

The presented flame and furnace AAS methods offer accurate, precise, and practical solutions for serum lithium and aluminium monitoring, meeting clinical and regulatory demands.

References

• Shimadzu Corporation. Measurement of Lithium and Aluminium in Human Sera. Application News No. A316A.
• National Institute of Standards and Technology. NIST SRM 909b Human Serum.