Determination of the alkalinity (p-value and m-value) in water

Importance of the Topic

Alkalinity is a fundamental parameter in water analysis, reflecting its capacity to neutralize acids and thus buffer pH changes. Monitoring both p-value (carbonate alkalinity) and m-value (total alkalinity) is essential for water quality control, environmental studies, and industrial processes where stable pH is critical.

Objectives and Study Overview

This application note demonstrates a fast and precise potentiometric titration method for determining carbonate and total alkalinity in tap water. The procedure follows recognized standards (EPA 310.1, Standard Methods 2320 B, ASTM D1067, EN ISO 9963-1/-2) and aims to showcase the performance of the OMNIS Professional Titrator equipped with a dUnitrode sensor.

Methodology and Instrumentation

• Sample: Untreated tap water, no pre‐treatment required.
• Titration: Sequential fixed‐point titration with standardized HCl to pH 8.2 (p-value) and pH 4.5 (m-value).
• Sensor: Metrohm dUnitrode with integrated Pt1000 for combined pH and temperature measurement.
• Instrument: OMNIS Professional Titrator featuring modular design, 3S Liquid Adapter technology, and software-controlled dosing and stirring.

Main Results and Discussion

The method delivers highly reproducible results over five replicates:

• Mean p-value: 0.039 mmol/L (relative SD 5.7 %).
• Mean m-value: 2.261 mmol/L (relative SD 0.1 %).

Potentiometric titration curves exhibit clear inflection points at the defined endpoints (pH 8.3 and pH 4.5), confirming method robustness and endpoint resolution.

Benefits and Practical Applications

• High accuracy and low variability in alkalinity measurements.
• Conformance with international standards for regulatory compliance.
• Modular titrator design supports diverse laboratory workflows and parallel titrations.
• 3S Liquid Adapter enhances safety and traceability of reagents.

Future Trends and Potential Applications

Advancements in automated titration are expected to integrate real‐time data analytics and LAB-AI connectivity for remote monitoring. Miniaturized sensors and microfluidic platforms may enable in‐field alkalinity measurements. Combining alkalinity titration with multi-parameter analysis (e.g., conductivity, dissolved CO2) could broaden environmental and industrial process control capabilities.

Conclusion

The described potentiometric titration method on the OMNIS Professional Titrator offers a reliable, standards-compliant approach for rapid determination of carbonate and total alkalinity in water. Its precision, automation, and modularity make it suitable for quality assurance in laboratories and on-site water monitoring.

References

• EPA Method 310.1
• Standard Methods 2320 B (Titration Method)
• ASTM D1067
• EN ISO 9963-1 and EN ISO 9963-2