Automated quality control of diesel using near-infrared spectroscopy

Key parameters for diesel fuel quality testing include the cetane index (ASTM D613), flash point (ASTM D56), density (ASTM D975), T95 (ISO 3405), and viscosity at 40 °C (ISO 3104). Usually, determining these properties is labor intensive and time consuming, requiring multiple analytical techniques and dedicated instrumentation. The OMNIS NIR Analyzer Liquid provides a fast, reliable, and reagent-free solution to simultaneously determine these diesel fuel properties without sample preparation. The precise temperature control ensures that all samples are measured in compliance with ASTM D8340, ASTM D8321, and ASTM D6122. Combined with the OMNIS Sample Robot M – NIR, the system offers fully automated operation for maximum lab efficiency.

The near-infrared spectra of diesel fuels (Figure 2), along with the corresponding reference values, were used to create prediction models for cetane number, cetane index, density, flash point, T95, and viscosity.

The quality of the prediction models was evaluated using the correlation diagrams shown in Figures 3–8 which display a very high correlation between the NIR prediction and the measured values using standard methods. Out of the total, 25% of the samples were selected as the validation set and the other 75% as a calibration set. The respective figures of merit (FOM) display the expected precision of a prediction during routine analysis.

This Application Note shows the feasibility of using NIR spectroscopy for the quality control of diesel. Determination of cetane index, cetane number, T95, density, flash point, and viscosity in diesel can be done simultaneously in a few seconds by using the OMNIS NIR Analyzer Liquid. The possibility of fully automated analysis in combination with the OMNIS Sample Robot M – NIR increases throughput, maximizing efficiency. With the OMNIS pre-calibration of diesel (6.06008.009), users can measure all the mentioned parameters from day one.