Separation of acylglycerols, FAME and FFA in biodiesel by size exclusion chromatography

Abstract

Size-exclusion chromatography separates solutes according to their molecular sizes. Free fatty acids (FFA), fatty acid methyl esters (FAME) and monoacylglycerols (MG) of vegetable oils or animal fats have very close molecular sizes and they cannot be baseline-separated on a single Phenogel column (100 Å, 300 mm 6 7.8 mm ID, 5 mm) by using tetrahydrofuran (THF) as the mobile phase. When toluene is used as the mobile phase, triacylglycerols (TG), diacylglycerols (DG), MG and FAME are well separated but there is no baseline resolution between DG and FAME. In addition, the elution order of MG and FAME is reversed. However, baseline separation of all the above lipid classes can be achieved by using toluene containing THF, acetone, dichloromethane, ethyl acetate or acetic acid as the solvent modifier. Acetic acid (0.25%) as the solvent modifier gives the best resolution and all the reference peaks are symmetrical. The detection limit of each class of lipids is 0.1 mg. The correlation coefficient values (between 1 and 100 mg) of all the lipid classes are better than 0.99. Thus, the determination of biodiesel products in the biodiesel reactor is very much simplified.

Effects of Crude Rice Bran Oil Components on Alkali‐Refining Loss

“…The purity of FFA (98+%; Fig. 1c) was determined by sizeexclusion HPLC [14]. Other reagents were analytical grade.…”

“…When the effects of RBO constituents on refining losses were assessed, the following correction was used for the component added: [14]. The ELSD drift tube was set at 30°C and the N 2 flow through the nebulizer was set at two bar.…”

Electrochemical Methods in Analysis of Biofuels

“…Santori et al [59] have proposed a liquid chromatographic method which successfully enables the monitoring of transesterification reaction. Other recent examples of biodiesel analysis by LC methods include determination of acylglicerols, free fatty acids and FAME by size exclusion chromatography [60] and determination of ester in glycerol phase after transesterification by a RP-LC method [61]. Besides chromatographic methods, some spectroscopic techniques have been also used to study the transesterification reaction and to determine organic contaminants in biodiesel.…”

Identification and Quantitation of Reaction Intermediates and Residuals in Lipase-Catalyzed Transesterified Oils by HPLC

“…Another limitation of the HPLC-UV system is its incompatibility with some commonly used solvents in lipid analysis such as chloroform and tetrahydrofuran; these solvents absorb strongly in the region of 190-220 nm, where most lipids absorb [11,20,21]. In contrast, the refractive index (RI) detector is a robust instrument for liquid chromatographic studies [12,17,22] that can be used with most solvent systems compared to the UV detector [11]. In spite of this, the HPLC-RI system has not been widely used in quantifying the products and co-products of transesterification reactions [15,21,22].…”

“…Additional advantages of the HPLC method include direct BD analyses, identification, and quantitation of the products and co-products of the reaction [10,14,17], thus minimizing the exposure to reagents and the extra cost associated with reagents and time. The HPLC system has been used with various detectors with different selectivities and sensitivities [10,18,19].…”