Determination of Trace Organic Acids and Inorganic Anions in Boric Acid-Treated Power Plant Waters Using an Automated Reagent-Free Ion Chromatography System

Importance of the Topic

In nuclear power plants, especially pressurized water reactors (PWRs), trace concentrations of anionic contaminants such as chloride, sulfate, and low-molecular-weight organic acids can accelerate stress corrosion cracking and increase maintenance costs. Monitoring these species in boric acid-treated waters at sub-µg/L levels is essential to maintain component integrity and ensure uninterrupted power generation.

Study Objectives and Overview

This work describes an automated, reagent-free ion chromatography (RFIC) method for simultaneous determination of trace organic acids (glycolate, acetate, formate) and inorganic anions in simulated PWR coolant waters containing boric acid and lithium hydroxide. The goals were to enhance accuracy, reproducibility, and sample throughput while minimizing manual handling and contamination risk.

Instrumentation Used

• RFIC system with dual piston pump, electrochemical eluent generator and inline degas module
• IonPac AG15 guard and AS15 analytical columns (2 mm)
• Continuously regenerated anion and cation trap columns (CR-ATC, CR-CTC II)
• High-volume autosampler with internal peristaltic pump (AS-HV)
• Suppressor-equipped conductivity detector (ASRS ULTRA II)

Methodology and Sample Preparation

Simulated samples (1000–2500 mg/L boric acid, 1.8–5 mg/L lithium) were prepared in rinsed tissue culture flasks. Calibration standards covering sub-µg/L to tens of µg/L ranges were generated online by the autosampler. An electrolytically generated KOH gradient (7→60 mM) eluted analytes after preconcentration on a 5×23 mm concentrator column (UTAC-ULP1). A 10 mL deionized water rinse preceded elution onto the 2 mm guard and AS15 analytical column to remove the borate matrix.

Key Results and Discussion

• Linearity: r² > 0.999 for all target anions.
• Detection Limits: Sub-µg/L MDLs achieved (e.g., fluoride 0.006 µg/L, acetate 0.034 µg/L).
• Precision: Retention time RSD < 0.1 %, peak area RSD < 3 % (n = 10).
• Matrix Tolerance: Up to 2500 mg/L boric acid did not affect quantitation of most analytes.
• Accuracy: Spike recoveries ranged from 89 to 112 % across all matrices.
• System Blanks: Inline spiking and trap columns maintained low background signals (< 0.15 µg/L chloride).

Practical Benefits and Applications

• Full automation reduces manual preparation and contamination risk.
• Electrolytic eluent generation yields stable baselines and reproducible gradients.
• Online standard handling improves trace-level accuracy.
• Method aligns with EPRI water chemistry guidelines for PWR corrosion control.

Future Trends and Possibilities for Use

Integration of microbore columns, advanced suppressor technologies, and on-line sample prep modules could further lower detection limits and increase throughput. Portable RFIC platforms and real-time data analytics may enable in-situ monitoring and predictive maintenance in power plant environments.

Conclusion

The described automated RFIC approach, combining electrolytic KOH eluent generation, regenerable trap columns, and online standard preparation, provides a robust solution for trace anion analysis in boric acid-treated power plant waters. It delivers high sensitivity, precision, and accuracy while minimizing labor and contamination.

References

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