Quality Control of Diesel

Significance of the Topic

Fuels can absorb water during production, transport, and storage. Excess moisture in diesel fosters microbial growth in storage tanks, leading to corrosion, sludge formation, and filter blockage, which ultimately damages fuel injection systems.

Objectives and Study Overview

This study evaluates near-infrared spectroscopy (NIRS) as a rapid and cost-effective alternative to Karl Fischer titration for determining water content in diesel fuel. The goal is to develop a predictive model that meets standard quality control specifications.

Methodology and Instrumentation

Diesel samples with water concentrations ranging from 103 to 379 mg/L were analyzed using a DS2500 Liquid Analyzer in transmission mode covering 400–2500 nm. Measurements were performed at a controlled temperature of 40 °C using disposable 8 mm pathlength vials. Reference moisture values were obtained via Karl Fischer titration. Data acquisition and model development were conducted using Vision Air Complete software.

• DS2500 Liquid Analyzer (400–2500 nm spectral range, temperature control)
• 8 mm disposable vial holder and vials
• Vision Air Complete spectroscopy software
• Karl Fischer titration for reference measurements

Main Results and Discussion

The NIRS calibration model showed a strong correlation (R2 = 0.9776) with reference KF titration values. The standard error of calibration was 16 mg/L, and cross-validation error was 21 mg/L, indicating reliable prediction performance for routine analysis.

Benefits and Practical Applications

The NIRS method delivers results in under one minute without requiring reagents, lowering operational costs and eliminating sample destruction. This approach supports efficient quality control of diesel fuels in both laboratory and production environments.

Future Trends and Opportunities

Integration with flow-through cells and automated sample robotics can enable inline monitoring. Extending NIRS models to additional fuel quality parameters and emerging biofuel blends, coupled with advanced data-processing algorithms, will further enhance process analytical technology.

Conclusion

Near-infrared spectroscopy provides a rapid, reagent-free, and accurate alternative to Karl Fischer titration for moisture determination in diesel fuel, aligning with industry standards and improving quality control efficiency.

Reference

• EN 590: Diesel fuel specification – maximum water content requirement.