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

Abstract

To develop new products and to apply measures of quality control quick and simple accessibility of additive composition in automo- tive 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 solu- tions 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 inten- sities 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.

Modified-Atmospheric Pressure-Matrix Assisted Laser Desorption/Ionization Identification of Friction Modifier Additives Oleamide and Ethoxylated Tallow Amines on Varied Metal Target Materials and Tribologically Stressed Steel Surfaces

“…In the reference lubricant mixture, i.e., both FM additives in base oil before tribotesting, all protonated molecular ions of the additives were identified in positive ion mode. High accuracy Orbitrap-MS yielded m / z 282.28 for oleic acid amide FM additive and m / z 302.30, m / z 316.32, m / z 330.34, m / z 346.33, m / z 356.35, m / z 358.37, m / z 372.35, and m / z 400.38 for corresponding structures of the polyethoxylated tallow amine with different lengths of saturated and unsaturated alkyl chains . The identities of the structure of additives were confirmed via CID-fragmentation of the corresponding precursor ions.…”

“…Atmospheric pressure-matrix assisted laser desorption/ionization-mass spectrometry (AP-MALDI-MS) was developed around the turn of the century − and has been strongly improved over the years by using various types of mass spectrometers ,− and different types of lasers. − In recent years, AP-MALDI has been widely used for analytical purposes in proteomics and the emerging field of lipidomics. − ,,− Only a little research has been carried out on additives such as cationic surfactants from wastewater, , as well as ethoxylated surfactants and antioxidants from lubricants, but no comprehensive study on organic friction modifiers (FM) utilizing AP-MALDI is known. Only recently, the general possibility to analyze friction modifier additives directly from base oil solutions via AP-MALDI-MS has been introduced . Furthermore, several materials have been used as AP-MALDI targets in previous studies, whereas the gold-covered metal target showed superior desorption/ionization yield. , …”

“…Only recently, the general possibility to analyze friction modifier additives directly from base oil solutions via AP-MALDI-MS has been introduced. 21 Furthermore, several materials have been used as AP-MALDI targets in previous studies, whereas the gold-covered metal target showed superior desorption/ionization yield. 15,20 Lubrication additives are important to improve friction properties of tribologically stressed surfaces.…”

“…AP-MALDI measurements of a combination of lubrication additives out of a base oil solution on the goldcovered steel target were already described elsewhere in great detail. 21 For this work, target materials have been varied to examine differences in ionization intensities and direct measurements of tribologically stressed surfaces have been undertaken. In addition to the gold-covered standard, model experiments were conducted on a 100Cr6 steel target and an aluminum target as well as three different copper alloys.…”

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

“…32,33 Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) is complimentary to the previously mentioned analytical methods and already a powerful tool to analyse proteomes and lipidomes. 34,35 Moreover, this technique has also been already successfully adopted for characterization of lubricant oils to detect additives such as anti-oxidants 36 and frictions modifiers 37 directly from base oil solutions as well as from tribologically stressed steel surfaces. 38 In addition, previous studies have used different surface materials as AP-MALDI targets, with the gold-coated steel target showing superior desorption/ionization yield.…”