AN-NIR-064
2023-09
Quality control of ammonium nitrate
Rapid and non-destructive moisture determination with NIRS
Summary
Specialty chemicals have to fulfill multiple quality requirements. One of these quality parameters, which can be found in almost all certificates of analysis and specifications, is the moisture content. The standard method for the determination of moisture content is Karl Fischer titration.
This method requires reproducible sample preparation, chemicals, and waste disposal. Alternatively, near-infrared spectroscopy (NIRS) can be used for the determination of moisture content. With this technique, samples can be analyzed without any preparation and without using any chemicals.
Result
The obtained Vis-NIR spectra (Figure 2) were used to create a prediction model for the moisture value determination. To verify the quality of the prediction model, correlation diagrams were created which display the correlation between Vis-NIR prediction and primary method values. The respective figures of merit (FOM) display the expected precision of a prediction during routine analysis.
Table 2. Figures of merit for the prediction of the moisture content using a DS2500 Solid Analyzer.
Figures of merit | Value |
---|---|
R2 | 0.840 |
Standard error of calibration | 0.011 g/L |
Standard error of cross-validation | 0.012 g/L |
Conclusion
This Application Note demonstrates the feasibility of NIR spectroscopy for the analysis of low moisture content in specialty chemicals, specifically ammonium nitrate. In comparison to the standard titration method, the reduction of analysis time and chemicals is a major advantage of NIR spectroscopy.
Table 3. Comparison of running costs for the determination of the moisture content with titration and NIR spectroscopy.
Lab method | NIR method | |
---|---|---|
Number of analyses (per day) | 10 | 10 |
Cost of operator (per hour) | $25 | $25 |
Costs of chemicals for water determination | $2 | $0 |
Time spent per analysis | 5 min | 1 min |
Total running costs (per year) | $8,288 | $938 |