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Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry of Friction Modifier Additives Analyzed Directly from Base Oil Solutions

To develop new products and to apply measures of quality control quick and simple accessibility of additive composition in automotive lubrication is important. The aim of this study was to investigate the possibility of analyzing organic friction modifier additives by means of atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS) from lubricant solutions without the use of additional separation techniques. Analyses of selected friction modifier ethoxylated tallow amines and oleic acid amide were compared using two ionization methods, positive-ion electrospray ionization (ESI) and AP-MALDI, using a LTQ Orbitrap mass spectrometer. Pure additives were characterized from solvent solutions, as well as from synthetic and mineral base oil mixtures. Detected ions of pure additive samples consisted mainly of [M + H]+, but also alkali metal adducts [M + Na]+ and [M + K]+ could be seen. Characterizations of blends of both friction modifiers from the base oil mixtures were carried out as well and showed significant intensities for several additive peaks. Thus, this work shows a method to directly analyze friction modifier additives used in the automotive industry from an oil blend via the use of AP-MALDI without any further separation steps. The method presented will further simplify the acquisition of data on lubricant composition and additives. Furthermore, it allows the perspective of analyzing additive reaction products directly from formulated oil blends.