Comparison of GC stationary phases for the separation of fatty acid methyl esters in biodiesel fuels

Abstract

The fatty acid methyl ester (FAME) content of biodiesel fuels has traditionally been determined using gas chromatography with a polar stationary phase. In this study, a direct comparison of the separation of FAMEs present in various biodiesel samples on three polar stationary phases and one moderately polar stationary phase (with comparable column dimensions) was performed. Retention on each column was based on solubility in and polarity of the phase. Quantitative metrics describing the resolution of important FAME pairs indicate high resolution on all polar columns, yet the best resolution, particularly of geometric isomers, is achieved on the cyanopropyl column. In addition, the separation of four C18 monounsaturated isomers was optimized and the elution order determined on each column. FAME composition of various biodiesel fuel types was determined on each column to illustrate (1) chemical differences in biodiesels produced from different feedstocks and (2) chemical similarities in biodiesels of the same feedstock type produced in different locations and harvest seasons.

Preparation of coffee oil-algae oil-based nanoemulsions and the study of their inhibition effect on UVA-induced skin damage in mice and melanoma cell growth

“…After various studies, the DB-WAX column was shown to provide a better resolution than the other two columns, HP-88 and HP-5MS, implying that a high-polar stationary phase is necessary to attain an adequate separation of fatty acids. A similar outcome was reported by Goding et al, 18 who studied the effect of GC column stationary phase on separation efficiency of fatty acids in biodiesel fuels. Figure 1 shows the GC chromatogram of fatty acids in coffee oil (A) and algae oil (B) by using a DB-WAX column and GC conditions shown in the "Materials and methods" section.…”

Gas chromatographic analysis of fatty acid methyl esters of milk fat by an ionic liquid derived from L-phenylalanine as the stationary phase

“…Other polar columns such as ZB-WAX plus and ZB-FFAP with dimensions of 30 m  0.25 mm  0.25 μm [40] allow a complete separation of 36 of the 37 fatty acids, except for the C18:1cis/transisomers, whereas for the more polar column BPX70, that is a cyanopropyl stationary phase, the separation of the 37 fatty acids is achieved.…”

Analysis of Biodiesel Feedstock Using GCMS and Unsupervised Chemometric Methods

“…Separations were performed using an Agilent 6890 gas chromatograph coupled with an Agilent 5937 mass spectrometer (Agilent Technologies, Santa Clara, CA) and have been presented in detail previously [3].…”

“…A variety of biodiesel feedstock sources, including soybean oil, waste grease, canola oil, and animal tallow were evaluated using chemometric methods. The cyanopropyl column chemistry (BPX70) was utilized for this investigation, as it provided the most optimal separation of individual FAME isomers [3]. The correlation coefficients between several key pairs of biodiesels, using the six most abundant peak areas in each biodiesel, are shown in Table 1.…”

“…Properties like biodiesel fuel quality and efficiency are dependent on the FAME content, which is in turn dependent on the feedstock from which the biodiesel is derived [2]. Gas chromatography coupled with mass spectrometry detection (GCMS) has effectively been utilized to separate and identify biodiesel FAMEs in order to generate a unique fingerprint for each biodiesel feedstock [1,[3][4][5][6][7] and references therein]. Previous work in our lab has evaluated optimal separation conditions for various biodiesel feedstocks (soybean oil, waste grease, canola oil, and tallows) analyzed on a variety of column chemistries [polyethylene glycol, phenyl-, and cyanopropyl-modified polydimethylsiloxane (PDMS)] [3].…”