Analysis of Ammonia as an Impurity in Fuel Cell Grade Hydrogen According to ISO 14687 Grade D Using a Gas Generator

Importance of the Topic

Hydrogen fuel cells require extremely low impurity levels to maintain performance and longevity; ammonia is a critical contaminant. The accurate detection of trace ammonia in hydrogen is essential for quality control and compliance with ISO 14687 Grade D standards.

Objectives and Study Overview

This study demonstrates the application of a non-suppressor ion chromatography method to quantify ammonia at the micromole-per-mole level in fuel-cell-grade hydrogen. Additionally, it validates the sampling and analysis procedure using a gas generator to simulate ammonia contamination.

Methodology and Instrumentation

• Ion Chromatograph: Shimadzu HIC-NS non-suppressor IC system equipped with a Shim-pack IC-C4 analytical column (150 mm × 4.6 mm I.D., 7 µm) and guard column
• Mobile Phase: 2.5 mM methane sulfonic acid at 1.0 mL/min, column temperature 40 °C, injection volume 100 µL
• Detection via conductivity measurement of ammonium ions
• Sampling protocol using a KIN-TEK 491 Flex2 gas generator to introduce ammonia gas into hydrogen with trapping in ultrapure water through dual impingers (500 mL/min for 30 min)

Results and Discussion

• Linearity: Calibration over 2.5–200 µg/L yielded R2 > 0.9995, ensuring reliable quantification at the ISO limit (25 µg/L equivalent to 0.1 µmol/mol ammonia)
• Repeatability: Seven replicates at 10 µg/L showed retention time RSD 0.04 % and peak area RSD 3.41 %, confirming method precision
• Gas Sampling Recovery: Samples spiked at 0.1 µmol/mol ammonia achieved recovery rates of 84–92 % across three replicates, demonstrating effective trapping and quantification

Benefits and Practical Applications

• The non-suppressor IC approach eliminates organic solvent extraction, reducing environmental impact and operating costs
• Use of a gas generator for spiking ensures traceable standard introduction and robust validation of sampling efficiency
• Combined with a suppressor IC, the system can analyze additional ionic impurities (halides, formate) for comprehensive fuel quality assessments

Future Trends and Potential Applications

• Integration of ion chromatography with mass spectrometry for enhanced sensitivity and selectivity at sub-µg/L levels
• Automation of trapping and direct gas-phase analysis for real-time hydrogen purity monitoring
• Development of portable IC systems for on-site quality control in hydrogen production and distribution
• Expansion to multi-analyte platforms addressing broader impurity profiles in emerging hydrogen technologies

Conclusion

The presented non-suppressor ion chromatography method meets the rigorous requirements of ISO 14687 Grade D for ammonia analysis in hydrogen. High linearity, precision, and validated sampling via gas generator confirm its suitability for quality assurance in fuel-cell applications.

Reference

• ISO 14687 2025 Hydrogen fuel quality – Product specifications
• KIN-TEK 491 Flex2 Gas Generator, KIN-TEK Analytical USA