Abstract/Summary

Fully formulated oils (FFOs) are petrochemical products employed as automotive lubricants and typically have complex compositions. Base oil, consisting of a hydrocarbon mixture derived from mineral or synthetic origin, typically makes up the majority of a formulation and serves to provide the principal lubricity of the finished product. To tailor the formulation to specific applications, increase functionality, and extend the in-use lifetime of the product, a range of additives may also be included in the formulation. These additives are speciality chemicals that serve specific roles within the formulation and often are divided into groups accordingly. Examples of such additive classes include antioxidants, detergents, antifoams, dispersants, zinc dialkyldithiophosphates (ZDDPs) and viscosity modifiers, amongst others. Ultimately, these additives can tailor both the physical and chemical properties of the final product. This combination of base oil and additives contributes to the overall high chemical complexity of the formulation. Mass spectrometry (MS) is particularly well-suited to the analysis of chemically complex samples, especially with modern high-resolution instruments that are capable of confidently identifying upwards of tens of thousands of unique chemical species in a single analysis. Additionally, mass spectrometry can be tailored to specific applications by using different ion sources, which can have the effect of changing the selectivity for different chemical compounds. Moreover, many MS setups permit coupling to a chromatographic technique in an on-line fashion, subsequently allowing separation of sample constituents prior to MS analysis. In light of this, the development of mass spectrometry-based techniques for analysing FFOs is of interest and could provide an attractive route to relatively rapid and automated analyses of a wide range of product components. In this work the development of two mass spectrometry-based methodologies applied to the analysis of FFOs is reported: a recently commercialised Soft Ionisation by Chemical Reaction in Transfer (SICRIT) ion source; and a more established high-performance liquid chromatography (HPLC) technique. Both techniques were coupled to a Thermo Fisher Scientific LTQ Orbitrap XL mass spectrometer. In the case of HPLC, well-documented electrospray ionisation (ESI) was used to generate ions for MS.