The qualitative and quantitative analysis of lubricant oil additives by direct analysis in real time-mass spectrometry

The application of direct analysis in real time combined with mass spectrometry (DART-MS) to the qualitative analysis of lubricant and oil additives, and the quantitative analysis of a lubricant antioxidant additive is reported. The additives were analysed alone and in the presence of a base oil, from filter paper, glass and steel surfaces, showing the potential of the DART-MS technique for the direct, rapid analysis of lubricant oil additives. The quantitative capabilities of the technique were evaluated for the antioxidant in an oil matrix at concentrations in the range 0.1-8mg/mL in oil (1-80μg antioxidant on spot), using a structural analogue of the antioxidant as an internal standard. The linearity (R2 =0.997), precision (% RSD=2.6%) and LOD (0.04mg/mL in oil) of the method demonstrates that DART-MS is capable of the rapid determination of additives in oil without pre-extraction.