Quality Control of Diesel

Importance of the Topic

Diesel fuel quality critically impacts engine performance, fuel efficiency, and emissions control. Key parameters such as cetane index, flash point, cold filter plug point (CFPP), distillation point D95, and viscosity define diesel suitability for various conditions. Traditional reference methods are time-consuming and require multiple instruments and reagents, motivating faster, reagentless approaches.

Objectives and Study Overview

This study evaluates the feasibility of using visible and near-infrared (Vis-NIR) spectroscopy with the XDS RapidLiquid Analyzer to simultaneously determine cetane index, flash point, CFPP, D95, and viscosity in diesel samples. The aim is to streamline quality control by reducing analysis time and simplifying workflows.

Methodology and Instrumentation

Diesel samples were measured in transmission mode over the 400–2500 nm range using a temperature-controlled sample compartment at 30 °C. Disposable 8 mm vials eliminated cleaning steps, and no chemical reagents or sample preparation were required. The Vision Air Complete software suite handled data acquisition, calibration, and prediction model development.

Instrumentation Used

• XDS RapidLiquid Analyzer (Metrohm #2.921.1410)
• Disposable glass vials, 8 mm diameter (Metrohm #6.7402.000)
• Vision Air 2.0 Complete spectroscopy software (Metrohm #6.6072.208)

Main Results and Discussion

Prediction models were built and validated against standard methods. Figures of merit include:

• Cetane index: R² = 0.991, SECV = 0.143
• Flash point: R² = 0.977, SECV = 2.50 °C
• CFPP: R² = 0.973, SECV = 2.24 °C
• D95: R² = 0.861, SECV = 3.47 °C
• Viscosity at 40 °C: R² = 0.983, SECV = 0.047 cSt

Strong correlations demonstrate that Vis-NIR spectroscopy can reliably predict these parameters, with the least accuracy observed for D95 due to its complex distillation profile.

Benefits and Practical Applications

• Analysis time under one minute without sample prep or reagents
• Single-instrument workflow reduces labor and operational costs
• Easy integration into routine QA/QC and process monitoring
• Disposable vials simplify handling and prevent cross-contamination

Future Trends and Opportunities

• Inline process control for continuous fuel quality monitoring
• Extended calibrations for biodiesel blends and alternative fuels
• Integration with machine learning and advanced chemometrics
• Portable NIR solutions for field and remote applications

Conclusion

Vis-NIR spectroscopy with the XDS RapidLiquid Analyzer provides a rapid, accurate, and reagent-free approach to diesel quality analysis. Implementing this technology can optimize laboratory workflows and deliver reliable data for critical fuel parameters.

Reference

No references were provided in the original document.