Chemical analysis of additives included in fully formulated oils using high-performance liquid chromatography-tandem mass spectrometry.

Rationale: Fully formulated oils (FFOs) are chemically complex petrochemical products composed of base oil and additive mixtures that are employed in automotive engines to provide lubrication. In particular, the additive portion of FFOs is often precisely controlled to tailor the resultant formulation to a specific role. Analysis of the additive composition of both used and unused FFOs is therefore of great importance within the petroleum, automotive, and wider engineering industries.

Methods: A simple and rapid reversed-phase high-performance liquid chromatography-tandem mass spectrometry method is reported herein for the analysis of a range of additives commonly encountered in FFO samples. Mass spectrometry was performed using an LTQ Orbitrap XL instrument using both positive- and negative-ion electrospray ionization. Tandem mass spectra were acquired in the data-dependent mode. FFO samples were analysed with minimal sample preparation, limited in this case to simple dilution steps.

Results: The reported method permits analysis of a range of antioxidant, detergent, and antiwear chemistries from various FFO samples in under 10 min. Additionally, it is demonstrated that additive confirmation can be performed and some structural information obtained using the data-dependent tandem mass spectrometry method. Furthermore, analysis of additives and corresponding degradation products within a used FFO is reported.

Conclusions: The results obtained using the reported methodology are of demonstrable use in numerous industries and applications, and readily return an abundance of information on the additive composition of a range of FFO samples. Anticipated applications of the methodology include but are not limited to quality control, suspected counterfeit analysis, and FFO degradation analysis.