Determination of Manganese in Brine (≥ 30% NaCl)

Significance of the Topic

Monitoring trace manganese levels in high-salinity sodium chloride brines is critical to prevent chlor-alkali membrane poisoning and to ensure the growth of high-quality salt crystals. Accurate determination at low µg/L concentrations supports product purity in industrial and chemical processes.

Objectives and Study Overview

This study presents an optimized ion-chromatographic method for quantifying manganese down to 10 µg/L in brines containing ≥ 30 % NaCl. Building on previous work for calcium and magnesium (Dionex AN 120), the approach modifies online sample preparation to selectively enrich manganese while minimizing sodium co-elution.

Methodology and Instrumentation

The procedure uses chelation ion chromatography with an online MetPac CC-1 preconcentration column. Samples are loaded in 2 M ammonium acetate (pH 5.4), rinsed with acetic acid and water to remove excess sodium, then eluted onto an IonPac CS12A analytical column with a 20 mM methanesulfonic acid eluent generated in-line. Suppressed conductivity detection quantifies manganese separately from alkaline earth metals.

Used Instrumentation

• Dionex ICS-3000 system
• DP Dual Pump, DC Detector/Chromatography module, EG Eluent Generator
• AS Autosampler, AM Automation Manager with 10-port valve
• MetPac CC-1 preconcentration column (4 × 50 mm)
• IonPac CG12A guard and CS12A analytical columns (4 × 250 mm)
• Chromeleon® 6.8 Chromatography Workstation

Key Results and Discussion

Calibration over 0–100 µg/L manganese yielded R² = 0.9985 with no detectable blank interference. Method precision showed retention time RSDs of 0.10–0.14 % and peak area RSDs of 7.5–9.0 %. Analysis of eight liquid and two solid brine samples returned manganese concentrations from < 1 to 91 µg/L. Spike-recovery experiments (20 µg/L) delivered recoveries between 72.9 and 119 %, confirming minor losses during preparation.

Benefits and Practical Applications

The automated chelation IC method provides:

• High sensitivity for manganese in challenging high-salt matrices
• Selective removal of sodium, reducing matrix effects
• Fully automated online sample preparation and elution
• Compatibility with routine QA/QC and industrial process control

Future Trends and Opportunities

Advances may include coupling with mass spectrometry for lower detection limits, development of multi-element chelation columns, and system miniaturization for field or on-line monitoring. Integration with advanced data analytics and LIMS will further streamline process control.

Conclusion

This optimized chelation IC technique enables reliable, low-µg/L manganese determination in high-salt brines via selective preconcentration and suppressed conductivity detection. The approach offers robust performance, high throughput, and is suitable for industrial and research laboratories.

References

• Dionex Application Note 120: Determination of Calcium and Magnesium in Brine; Dionex Corporation, 1998.