Quality control of Ammonium Nitrate

Importance of the Topic

Moisture content is a critical quality attribute for specialty chemicals like ammonium nitrate. Accurate and rapid moisture determination ensures product performance, stability, and safety. Traditional Karl Fischer titration delivers reliable results but requires reagents, sample preparation, and disposal steps, creating operational bottlenecks.

Study Objectives and Overview

The primary aim of this investigation is to evaluate near-infrared (NIR) spectroscopy as an alternative approach for moisture analysis in ammonium nitrate. The study compares NIR predictions against reference moisture values obtained by volumetric Karl Fischer titration, focusing on accuracy, speed, and cost efficiency.

Methodology

Samples of ammonium nitrate were measured in reflection mode across the full 400–2500 nm range using a DS2500 Solid Analyzer. A rotating large sample cup minimized particle-size effects by averaging multiple measurement positions. No sample pretreatment or chemicals were required. Spectral data were collected and processed with Vision Air Complete software to develop a calibration model for moisture prediction.

Used Instrumentation

• DS2500 Solid Analyzer (400–2500 nm)
• DS2500 Large Sample Cup (rotating accessory)
• Vision Air 2.0 Complete software for data acquisition and model development

Main Results and Discussion

The NIR calibration model achieved a coefficient of determination (R²) of 0.84, with a standard error of calibration (SEC) of 0.011 mg/L and a standard error of cross-validation (SECV) of 0.012 mg/L. Correlation plots demonstrated good agreement between NIR-predicted moisture values and Karl Fischer reference results, confirming the method’s reliability for routine analysis.

Benefits and Practical Applications

Compared with conventional titration, NIR offers:

• Non-destructive, preparation-free analysis
• Rapid turnaround (< 1 min per sample vs. 5 min)
• Elimination of titration chemicals and associated waste
• Significant cost savings—annual running costs reduced from approx. $8,300 to $940 (for 10 analyses/day)

This approach is ideal for quality control in industrial laboratories and production sites, enabling high throughput and greener workflows.

Future Trends and Applications

Advancements in NIR instrumentation and data analytics open avenues for:

• Integration into continuous process monitoring
• Expansion to other quality parameters (e.g., purity, particle size)
• Deployment of portable or inline NIR sensors for real-time feedback
• Enhanced predictive performance through machine learning and advanced chemometrics

Conclusion

This study confirms that NIR spectroscopy provides a fast, reliable, and cost-effective method for moisture determination in ammonium nitrate. By eliminating sample preparation and reagents, NIR supports sustainable laboratory practices while meeting industrial quality requirements.