Photometric EDTA titration of manganese sulfate according to Ph. Eur. and USP

Importance of the Topic

The accurate quantification of manganese sulfate is critical in quality control across pharmaceutical, agricultural, and industrial sectors. The photometric EDTA titration method ensures compliance with stringent pharmacopoeial standards and offers high precision and reproducibility.

Objectives and Study Overview

This application note outlines a robust photometric titration protocol for manganese sulfate using EDTA complexation. The procedure aligns with European Pharmacopoeia and USP specifications, detailing sample handling, indicator selection, and endpoint detection via an Optrode at 610 nm.

Methodology and Instrumentation

The analysis involves dissolving approximately 0.150 g of the sample in water, followed by addition of ascorbic acid, NH₃/NH₄Cl buffer (pH 10), and Eriochrome Black T indicator. Titration is performed with 0.1 mol/L Na₂EDTA under defined conditions:

• Titration mode: MET U
• Measurement drift: 50 mV/min
• Waiting time: 0–26 s
• Volume increment: 0.1 mL
• Endpoint criterion: 30 mV (greatest slope)
• Stirring speed: 8

The setup employs:

• 907 Titrando
• 800 Dosino modules with 10, 20, and 50 mL dosing units
• 802 Rod Stirrer and 815 Robotic USB SP
• 250 mL sample beaker and rack for 28 samples
• Optrode sensor at 610 nm for photometric endpoint detection

Solutions include 0.1 mol/L Na₂EDTA titrant, ascorbic acid, Eriochrome Black T indicator, and ammonia/ammonium chloride buffer.

Main Results and Discussion

The method yielded an average assay of 99.19 ± 0.196 % MnSO₄·H₂O (n=6), demonstrating excellent precision and accuracy. Photometric detection provided clear endpoint identification, minimizing operator bias and enhancing repeatability.

Benefits and Practical Applications

This titration approach offers:

• High throughput with minimal sample preparation
• Automation compatibility for routine QA/QC workflows
• Compliance with Pharm. Eur. and USP guidelines
• Robust endpoint detection through photometric measurement

Future Trends and Potential Applications

Advancements may include the integration of inline sensors for continuous monitoring, miniaturized titration systems for smaller sample volumes, and incorporation of chemometric data analysis for enhanced method development. Green chemistry adaptations and AI-driven titration control represent emerging opportunities.

Conclusion

The photometric EDTA titration method described provides a reliable, precise, and automated solution for manganese sulfate determination, meeting pharmacopoeial requirements and supporting high-throughput analytical environments.

Reference

• Titration Application Note T-889. Photometric EDTA titration of manganese sulfate according to Ph. Eur. and USP.