Determination of Trace Cations in Power Plant Waters Containing Morpholine

Importance of the Topic

Power plant water treatment uses morpholine and ammonium to protect against corrosion and control pH. Accurate determination of trace cations such as Li+, Na+, K+, Mg2+, and Ca2+ in these matrices is critical to maintain system integrity and performance.

Objectives and Study Overview

The goal of this study is to develop and validate an ion chromatography method capable of quantifying trace cations in power plant waters containing high levels of morpholine and ammonium. Key challenges include peak resolution and matrix compatibility.

Methodology and Instrumentation

The method employs a Dionex ion chromatography system with:

• IonPac CS14 (2 mm) analytical column
• Two IonPac CG14 (2 mm) guard/concentrator columns
• Suppressed conductivity detection using a CSRS-I (2 mm) suppressor
• Eluent: 8 mM methanesulfonic acid, with or without 5% acetonitrile (v/v)
• Flow rates: 0.25 mL/min (eluent), 1.0 mL/min (rinsing)
• Sample volume: 1.0 mL concentrated on CG14

The sample is loaded directly without pretreatment, concentrated on the guard column, rinsed (optionally with acetonitrile), then eluted and separated.

Main Results and Discussion

Calibration over multiple levels showed high linearity (r2 > 0.987). Reproducibility tests (21 replicates) yielded relative standard deviations below 4.2% for concentration and 0.8% for retention time. Adding 5% acetonitrile improved morpholine peak shape, separation from magnesium, and response of divalent cations. The 2 mm system offered lower flow rates, reduced waste, and enhanced suppression capacity compared to 4 mm alternatives.

Benefits and Practical Applications

This approach enables both on-line and grab sample analysis without complex pretreatment. The concentrator column enhances sensitivity for trace cations in challenging morpholine-ammonium matrices. Lower solvent consumption and waste generation support sustainable laboratory practices.

Future Trends and Potential Applications

Emerging developments may include integrating advanced suppressor technologies, further miniaturization for field-deployable systems, and expanded applications to other amine-based corrosion inhibitor matrices and real-time monitoring solutions.

Conclusion

The presented ion chromatography method provides a robust, sensitive, and reproducible solution for determining trace cations in power plant water containing morpholine. Its adaptability and performance make it suitable for routine monitoring and industrial quality control.

Used Instrumentation

• Dionex Advanced Gradient Pump (AGP)
• Liquid Chromatography Module (LCM-3) with Rheodyne injector or equivalent
• Sample Preparation Module (SPM)
• Conductivity Detector Module (CDM-3)
• Sample Loading Pump RP-1
• IonPac CS14 analytical column and IonPac CG14 guard/concentrator columns
• CSRS-I suppressor in auto-suppression mode

References

1. Bostic D.; Burns G.; Harvey S. Journal of Chromatography 1992, 602, 163–171.