New FTIR Analysis Methods for a Better Understanding of Lubricants and Base Oils with eraspec oil.

More precise insights into oil composition and properties

Understanding the chemical composition of lubricants and base oils is essential for manufacturers, analytical laboratories, and industrial operators. To meet these requirements, Fourier-transform infrared (FTIR) spectroscopy offers new opportunities for investigating oil composition and condition. With eralytics’ eraspec oil analyzers, detailed information can be obtained quickly, both in the laboratory and directly on-site.

FTIR spectroscopy for lubricant analysis

FTIR spectroscopy is based on the interaction between infrared radiation and the molecules present in a sample. Different chemical compounds absorb infrared radiation at characteristic frequencies, producing a spectrum that serves as a molecular fingerprint of the oil.

By interpreting this spectrum, analysts can monitor several chemical processes, including oxidation, nitration, and sulfation. The technique can also help detect certain contaminants and assess changes in additive concentrations as lubricants age.

This approach provides valuable insights into lubricant performance, helps identify early signs of degradation, and supports more effective preventive maintenance strategies.

Improving base oil characterization through chemometric models

Beyond monitoring used lubricants, FTIR spectroscopy also offers promising possibilities for characterizing base oils, which are key components in lubricant formulations.

One particularly important parameter is the aniline point, which is used to assess the solvency characteristics of a base oil. This property influences its ability to dissolve certain additives and maintain compatibility between the different components of a lubricant formulation.

An exploratory study using the eraspec oil analyzer demonstrated the potential to estimate the aniline point directly from FTIR spectra using an appropriate chemometric model. The study examined 30 base oil samples with kinematic viscosities at 40 °C ranging from 8 to 115 mm²/s and aniline points between 70 and 105 °C.

The regression model developed for the study achieved a standard error of calibration of 1 °C. These findings represent a promising proof of concept for indirectly evaluating selected base oil properties using infrared spectroscopy. Further validation with a broader range of samples is required to establish the robustness of this approach across different industrial applications.

In the future, this method could simplify base oil characterization and reduce the need to rely exclusively on certain conventional testing procedures.

Technological advances for improved sensitivity and measurement reliability

Recent developments in the eraspec oil analyzer have further enhanced its lubricant analysis capabilities. The instrument incorporates a triple-cell measurement architecture consisting of a 100 µm measuring cell, an additional 500 µm cell, and a reference cell.

This configuration allows the optical path length to be adapted to the concentration of the target compounds, improving the detection of certain substances present at low concentrations, including antioxidants, water, and esters.

Another important development concerns water quantification. Conventional FTIR measurements can be affected by oxidation products and additives whose spectral signals overlap with the water signal. To address these interferences, eralytics has developed a chemometric model calibrated against the Karl Fischer reference method in accordance with ASTM D6304-B.

According to the manufacturer, this approach improves low-level water detection, with results available in less than two minutes.

Automated lubricant identification

Spectral analysis is not limited to chemical characterization. It can also help verify the identity of unused lubricants.

The eraspec oil analyzer automatically compares the spectrum of a sample with reference spectra stored in its integrated database. A correlation algorithm then identifies the reference profile that most closely matches the analyzed sample.

This functionality is particularly useful for incoming quality control, verification of delivered products, and reducing the risk of confusion between different lubricant formulations. It helps strengthen quality assurance procedures and prevent product identification errors.

Fast on-site analysis

One of the main advantages of the eraspec oil analyzer is its autonomous and automated operation. The sample is introduced using an integrated pump, without requiring complex preparation or solvents for the measurement process described by the manufacturer.

Results are generally available within 60 to 120 seconds, depending on sample viscosity. The instrument can monitor several parameters associated with oil degradation, contamination, and additive depletion. Additional parameters, such as total acid number (TAN) and total base number (TBN), can also be estimated using suitable chemometric models.

Performing these analyses directly on-site can accelerate decision-making and reduce the delays associated with routinely sending samples to an external laboratory. Results must nevertheless be interpreted in light of calibration methods, oil characteristics, and the validation requirements of each application.

Conclusion: Better control of lubricant quality and performance

Advances in FTIR spectroscopy, combined with improvements in chemometric modeling and automated spectral processing, are expanding the possibilities for analyzing lubricants and base oils.

The eraspec oil platform illustrates this progress by combining rapid measurements, lubricant condition monitoring, product identification, and the investigation of additional physicochemical properties. Estimating the aniline point directly from FTIR spectra is a particularly interesting development for more comprehensive base oil characterization.

These innovations offer new opportunities for quality control, lubricant formulation, and industrial maintenance. They also highlight the value of infrared spectroscopy as a complementary analytical tool alongside conventional testing methods, provided that appropriate models and rigorous validation procedures are used.