Establishing quantitative structure-property relationships (QSPR) of diesel samples by proton-NMR & multiple linear regression (MLR) analysis

The relationships between the structural parameters of diesel samples as observed by H-1 NMR spectroscopy have been established with their physicochemical properties using multiple linear regression (MLR). About 60 commercial diesel samples were taken up for this study and their various physicochemical properties were determined using the standard IF, DIN, or ISO methods. The properties included density, cetane number, cetane index, viscosity, sulfur content, final boiling point, and the percentage of volume distillable till 350 degreesC. The H-1 MMR spectra of the diesel samples were correlated with the properties using stepwise multiple linear regression, and resulted in high correlations. The method allows for the determination of about 7 properties of commercial diesel sample from a single H-1 NMR spectrum. The present model is restrained to similar types of diesel samples, when intend to be used for predictive purposes. The presence of low levels of diesel additives (like cetane improvers or pour point depressant, etc.), which are not detectable by NMR, also pose limitation to the method, as emerged from the present feasibility study.