Determination of residual automotive lubricant oil and residual solvent used in a dry wash as adulterants in Brazilian S-10 diesel (B7) using mid-infrared spectroscopy data and chemometric methods

Abstract

This paper presents methodologies for safe discrimination between adulterated and unadulterated samples of Brazilian S-10 diesel using mid-infrared (MIR) spectroscopy and partial least squares discriminant analysis (PLS-DA). The samples of unadulterated and adulterated Brazilian S-10 diesel were classified correctly into their respective groups, that is, the PLS-DA models showed 100% correct classification for samples of a test set with high levels of sensitivity and specificity to discriminate between unadulterated and adulterated samples with residual automotive lubricant oil (RAL) and residual solvent used in a dry wash (RSUDW). In order to extend the work, the adulterant content was predicted using partial least squares (PLS), which showed a good correlation between the reference values with R = 0.9999 for RAL and RSUDW in Brazilian S-10 diesel. The methodologies were validated, estimating specific figures of merit for the qualitative and quantitative multivariate analysis and were able to detect and quantify RAL and RSUDW in Brazilian S-10 diesel. The results from both methods were satisfactory for both qualitative and quantitative detection of RAL and RSUDW, as adulterants in Brazilian S-10 diesel (B7), commonly used in Brazil. Therefore, the proposed methodologies for the quantification of adulterants and discrimination between adulterated and unadulterated samples of Brazilian S-10 diesel are fast, practical, economical and efficient and can be used by industries and fuel distributors.