Preparation of fatty acid methyl esters for gas-liquid chromatography.
A convenient method using commercial aqueous concentrated HCl (conc. HCl; 35%, w/w) as an acid catalyst was developed for preparation of fatty acid methyl esters (FAMEs) from sterol esters, triacylglycerols, phospholipids, and FFAs for gas-liquid chromatography (GC). An 8% (w/v) solution of HCl in methanol/water (85:15, v/v) was prepared by diluting 9.7 ml of conc. HCl with 41.5 ml of methanol. Toluene (0.2 ml), methanol (1.5 ml), and the 8% HCl solution (0.3 ml) were added sequentially to the lipid sample. The final HCl concentration was 1.2% (w/v). This solution (2 ml) was incubated at 45 degrees C overnight or heated at 100 degrees C for 1-1.5 h. The amount of FFA formed in the presence of water derived from conc. HCl was estimated to be <1.4%. The yields of FAMEs were >96% for the above lipid classes and were the same as or better than those obtained by saponification/methylation or by acid-catalyzed methanolysis/methylation using commercial anhydrous HCl/methanol. The method developed here could be successfully applied to fatty acid analysis of various lipid samples, including fish oils, vegetable oils, and blood lipids by GC.
Ichihara
Ken'ichi
K
Biological Chemistry Graduate School of Agricultural Science, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan. ichihara@kpu.ac.jp
Fukubayashi
Yumeto
Y
D002853:Chromatography, Liquid; D004952:Esters / Q000737:chemistry*; D005227:Fatty Acids / Q000737:chemistry*; D005395:Fish Oils / Q000737:chemistry; D006851:Hydrochloric Acid / Q000737:chemistry; D007202:Indicators and Reagents / Q000737:chemistry; D007700:Kinetics; D008055:Lipids / Q000097:blood / Q000737:chemistry; D000432:Methanol / Q000737:chemistry; D008745:Methylation; D010938:Plant Oils / Q000737:chemistry; D012995:Solubility; D013696:Temperature; D014050:Toluene / Q000737:chemistry; D014867:Water / Q000737:chemistry
D004952:Esters; D005227:Fatty Acids; D005395:Fish Oils; D007202:Indicators and Reagents; D008055:Lipids; D010938:Plant Oils; D014867:Water; D014050:Toluene; D006851:Hydrochloric Acid; D000432:Methanol