Determination of aluminum and zirconium in antiperspirants

Importance of the Topic

The control of aluminum and zirconium levels in antiperspirant formulations is critical for product safety, efficacy and regulatory compliance. Zirconium aluminum glycine (ZAG) complexes are widely used active ingredients in antiperspirants due to their superior performance in reducing perspiration. Reliable, streamlined analytical methods are essential for routine quality control in pharmaceutical and personal care industries.

Objectives and Study Overview

This application note demonstrates a rapid, automated procedure for the consecutive determination of zirconium and aluminum in a single beaker. The method aligns with USP complexometric titration principles while minimizing laborious digestion and manual titration steps. Key goals include reducing sample handling, improving throughput, and maintaining accuracy consistent with pharmacopeial standards.

Methodology

Sample Preparation:

• Zirconium and aluminum standard solutions were combined and diluted with water.
• A drop of xylenol orange indicator added prior to titration.

EDTA Titration for Zr:

• pH adjusted to 1.0 using pH 1 buffer.
• EDTA (0.10 mol/L) delivered by OMNIS Titrator.
• Endpoint detected optically at 574 nm when pink shifts to yellow.

Buffered Back-Titration for Al:

• pH raised to 4.7 with acetate buffer.
• Excess EDTA added, then back-titrated with Bi(NO₃)₃ (0.05 mol/L).
• Endpoint observed at 574 nm as solution changes from yellow to purple.

Instrumentation

• OMNIS Professional Titrator with dosing modules and 3S Liquid Adapter technology.
• OMNIS Sample Robot S for automated sample handling (optional expansion to L-size robot).
• Optrode photometric sensor operating at selectable wavelengths (574 nm for this method).

Main Results and Discussion

Representative titration curves for zirconium at pH 1 and aluminum at pH 4.7 show clear, sharp equivalence points. Analyses of standard mixtures yielded accurate recovery of both metals with high precision. The one-beaker approach eliminated intermediate transfers and reduced total analysis time compared to traditional manual titrations.

Benefits and Practical Applications

• Fully automated sequential titration in a single vessel.
• Reduced sample preparation and operator workload.
• High reproducibility suitable for routine QC in laboratories.

Future Trends and Opportunities

The integration of robotic sample handling and advanced titration software paves the way for higher throughput and multi-analyte determination. Potential extensions include nonaqueous titrations, other metal‐ligand systems, and coupling with spectroscopic detectors for comprehensive formulation analysis.

Conclusion

The described method provides a rapid, reliable solution for simultaneous determination of zirconium and aluminum in antiperspirant complexes. Leveraging OMNIS automation and optical sensing simplifies compliance with USP monographs while enhancing laboratory efficiency.

References

United States Pharmacopeia (USP) complexometric titration monographs.