Rational biodiesel production from oxidation stability perspective: Evaluation of lipid-soluble carbonyl compound formation in the seed oil and biodiesel with long-term storage

The exploration of appropriate feedstock and catalytic transesterification hinders the practical application of biodiesel. Here, we introduced rational biodiesel production from oxidation stability perspective and evaluated the lipid-soluble carbonyl-containing oxidation products in long-term stored biodiesel samples that prepared from different oil source, catalyst for production, and ester bond type. A stable isotope labeling method based on liquid chromatography-high resolution-mass spectrometry (SIL-LC-HRMS) detection is established using a pair of labeling reagents namely1-(2-hydrazinyl-2-oxoethyl)pyridin-1-ium chloride (GP) and [2H5]1-(2-Hydrazinyl-2- oxoethyl)pyridin-1-ium chloride ([2H5]GP) for lipid-soluble carbonyl-containing oxidation products, including aldehydes and ketones. The main benefits of SIL-LC-HRMS are its sensitivity, selectivity, and feature coverage towards carbonyl-containing compounds and realized their non-targeted screening and relative quantification from complex matrices. Using SIL-LC-HRMS analysis, it was estimated the distribution and formation of 131 carbonyl compounds in three different kinds of second-generation feedstock and biodiesels with one-year storage in the dark. Double bond equivalent (DBE)-number of carbon (nC) plots and hierarchical clustering heatmap analysis reveal the effect of the oil source, catalyst type, and alkyl ester bond type on the variance in carbonyl compound formation during long-term biodiesel storage, arguably the most crucial factor oxidation stability in rational biodiesel production. The carbonyl formation and their variations in biodiesel samples are also discussed by theoretically calculating the bond dissociation energy for the primary constituent of seed oil and biodiesel.