Combination of mid-infrared spectroscopy and curve resolution method to follow the antioxidant action of alkylated diphenylamines

The inhibition of the oxidation of lubricating base oils by dinonyldiphenylamine has been studied by combined Fourier transform infrared (FTIR) spectroscopy and multivariate curve resolution–alternating least squares (MCR-ALS) method. This allowed to extract chemical information during the induction period. The substituted diphenylamines are progressively converted to a degraded form which can be followed with the chemometric analysis. When concentration of dinonyldiphenylamine is too low, the induction period ends and the oxidation of the base oils begins.