Conductivity, pH value, alkalinity, hardness, and chloride in tap water

Importance of the Topic

Routine monitoring of tap water quality is critical for public health and regulatory compliance. Key chemical parameters such as conductivity, pH, alkalinity, hardness and chloride concentration offer insights into water purity, corrosion risk and potential contamination.

Objectives and Study Overview

This application note demonstrates a fully automated workflow that integrates sample handling, multi-parameter measurement and titration in a single run. The goal is to determine conductivity (ISO/EN/ASTM/EPA), pH (EN ISO/ASTM/EPA), alkalinity (EN ISO/ASTM/EPA), calcium and magnesium hardness (ISO/ASTM/EPA) and chloride (ISO/ASTM/EPA) in tap water without manual preparation.

Methodology and Instrumentation

The system couples a robotic sample processor with potentiometric titration and conductivity modules. Prior to analysis, sensors are calibrated automatically. The sequence is:

• Conductivity measurement directly in the sample beaker with a 5-ring conductivity cell and integrated Pt1000 temperature probe.
• Automated aliquot transfer to Vessel 1 for pH measurement (iAquatrode Plus) and alkalinity titration with HCl.
• pH adjustment using TRIS buffer and complexometric titration with EDTA in the same vessel to determine Ca and Mg.
• Aliquot transfer to Vessel 2 for chloride determination by silver nitrate titration following acidification.
• Automated cleaning of vessels and electrodes.

The main hardware components used:

• 815 Robotic USB Sample Processor XL
• 843 Peristaltic Pump Station
• 856 Conductivity Module with 5-ring conductivity cell
• 905 Titrando high-end potentiometric titrator
• iAquatrode Plus combined pH electrode
• Polymer membrane Ca-ISE
• iAg Titrode for chloride titration

Results and Discussion

The turnkey system delivers all parameters in under 15 minutes per sample with excellent reproducibility (n = 10):

• Conductivity: 567.4 µS/cm (RSD 0.84%)
• pH: 7.83 (RSD 0.32%)
• Alkalinity: 5.44 mmol/L (RSD 0.09%)
• Calcium: 84.57 mg/L (RSD 0.50%)
• Magnesium: 19.66 mg/L (RSD 1.74%)
• Total hardness: 2.92 mmol/L (RSD 0.62%)
• Chloride: 10.87 mg/L (RSD 1.51%)

Recorded titration curves exhibit clear equivalence points for both alkalinity and hardness endpoints, confirming precise endpoint detection.

Benefits and Practical Applications

• Eliminates manual sample preparation and transfers, reducing human error.
• High automation increases throughput and frees operator time.
• Complies with multiple international standards in a single run.
• Suitable for routine QA/QC in water treatment, environmental monitoring and industrial quality control.

Future Trends and Opportunities

Next-generation water analysis will leverage inline sensors, miniaturized sampling devices and AI-driven method optimization. Integration with LIMS and remote monitoring platforms can further enhance data traceability and laboratory productivity.

Conclusion

The presented fully automated system consolidates conductivity, pH, alkalinity, hardness and chloride analysis into one streamlined workflow. By automating sample handling, sensor calibration and titrations, it achieves rapid, reproducible results while minimizing operator intervention, thereby boosting laboratory efficiency.