The aim of this work is to quantify three different antioxidants in biodiesel - Santoflex, baynox, and tocopherol-using Middle Infrared (MIR) spectroscopy and chemometrics. For the construction of the models, 28 samples containing an antioxidant in the range of 0.1 to 500 mg/kg in biodiesel were used. We developed three models based on PLS 1 multivariate calibration method to quantify each of the three antioxidants separately and a model based on PLS 2 method to quantify simultaneously all the antioxidants.
All models were compared to the values of root mean square error of calibration (RMSEC) and validation (RMSEP). For the baynox, santoflex, and tocopherol antioxidants quantification using PLS 1, the values of RMSEC and RMSEP were 37.2, 18.8, 9.0 mg/kg, and 26.7, 21.1, 68.6 mg/kg, respectively. In simultaneous determination of these three compounds (tocopherol, santoflex, and baynox) using PLS 2, the values observed by RMSEC and RMSEP were 7.7, 1.1, 7.3 mg/kg and 29.9, 4.2, 28.4 mg/kg, respectively.
The methodology described here is fast, non-destructive, and can be used for quality control of antioxidants present in biodiesel.
