Materials
Biodiesel samples were acquired from the following sources: 1) CaME was from Archer Daniels Midland (Decatur, IL, USA); 2) PME produced by Sime Darby Biodiesel Sdn. Bhd. (Selanger, Malaysia) with assistance from the Malaysian Palm Oil Board (Washington, DC, USA); and 3) SME was from Ag Environmental Products (Lenexa, KS, USA). According to the fuel producers, these biodiesel samples were not treated with performance enhancing additives including antioxidants. Fatty acid concentration profiles for these biodiesel fuels are presented in Table S1 in the supporting information.
Pure MeC18:1 (99.5 ± 0.1 % 9(Z)-octadecenoic acid methyl ester) and MeC18:2 (99.0 ± 0.1 % 9(Z),12(Z)-octadecadienoic acid methyl ester) were supplied by Nu Chek Prep (Elysian, MN, USA). The purities of MeC18:1 and MeC18:2 were verified by analysis with a PerkinElmer (Waltham, MA, USA) Clarus 500 gas chromatograph (GC) with a flame ionization detector (FID) using an HP-88 column (30 m x 0.250 mm x 0.20 μm) from Agilent (Santa Clara, CA, USA). The carrier gas was hydrogen and injector and detector temperatures were 240 °C and 280 °C. The temperature program was: 1) hold at 100 °C for 5 min; 2) ramp at 10 °C min−1 to 220 °C; 3) hold at 220 °C for 15 min. Three replicate analyses were performed and results for the pure FAME were reported as average values.