Atmospheric pressure matrix‐assisted laser desorption/ionization mass spectrometry of engine oil additive components

Abstract

The efficiency of lubricants strongly depends on the content of functional additives. In order to assess the chemical and structural changes taking place in the lubricating oil and its additives during operation, it is essential to develop a method for simple and prompt analysis.Methods: Two single additives as well as a fully formulated engine oil were analysed using an atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) source coupled to a linear trap quadrupole Orbitrap XL hybrid tandem mass spectrometer and compared with results obtained by means of electrospray ionization (ESI) including additional low-energy collision-induced dissociation (LE-CID). The identification of additives directly from technical surfaces was simulated by using steel substrates as AP-MALDI targets with varying roughness. Results: After assessment and selection of the most suited AP-MALDI matrix it was found that pure additives such as calcium sulfonate and zinc dialkyldithiophosphates (ZDDPs) could well be identified with abundant signal intensity based on their elemental composition. Molecular identification was corroborated by LE-CID in ESI mode. Additionally, additives present in the fully formulated commercial oil such as ZDDPs and salicylates could be reliably identified based on the elemental composition of the deprotonated molecules by means of the Orbitrap unit on different substrates including steel surfaces with high roughness.Conclusions: AP-MALDI is an efficient technique for determination of lubricant additives directly from commercial oil blends. Identification of additive components was also achieved on steel surfaces with high roughness as applied in tribological systems and thus it is expected that it will be possible to assess additive degradation in real applications, enabling more effective and timely maintenance measures.

Nanoparticle-based applications by atmospheric pressure matrix assisted desorption/ionization mass spectrometry

“…Further, this work revealed that AP MALDI is an efficient technique for directly determining lubricant additives from commercial oil products. 122 In 2023, Maurice and co-workers developed and optimized 48 well graphene nanoplatelets (GNP) doped AP MALDI target plates for the fast-screening analysis of additives in electronics and plastic consumer products, while a total of 56 additives including antioxidants, flame retardants, plasticizers, UV-stabilizers, and UV-filters were identified. 123 This helps in understanding the level of pollution in the environment and taking necessary measures to protect the environment and human health.…”

Oil Degradation Patterns in Diesel and Petrol Engines Observed in the Field—An Approach Applying Mass Spectrometry

“…To separate the complex mixture of base oil components and additives, mass spectrometry is frequently combined with chromatographic techniques, such as gas chromatography (GC) [16,17] or liquid chromatography (LC) [18,19], which typically involves increased time and more elaborate sample preparation. For direct comprehensive chemical analysis of lubricants by MS, ambient ionization techniques such as desorption electrospray ionization (DESI) [20,21], matrix-assisted laser desorption ionization (MALDI) [22], direct analysis in real time (DART) [23], and atmospheric solids analysis probe (ASAP) [24] are becoming more widespread and popular. Instruments with high resolution and mass accuracy allow additives to be identified without complex sample preparation or the use of standards, as demonstrated by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) [25] or dielectric barrier discharge ionization mass spectrometry (DBDI-MS) [26].…”