Comparison of Catalysts for Direct Transesterification of Fatty Acids in Freeze- Dried Forage Samples
نویسندگان
چکیده
Our objective was to compare 1.09 M methanolic HCl to 14% BF3 in methanol as catalysts for direct transesterification of fatty acids in freeze-dried forage samples. Samples included blue grama (Bouteloua gracilis), fringed sage (Artemisia frigida), western wheatgrass (Pascopyrum smithii), needle-and-thread (Stipa comata), dalmation toadflax (Linaria dalmatica), needleleaf sedge (Carex eleocharis), and scarlet globemallow (Sphaelercea coccinea). Thin layer chromatographic evaluation revealed complete conversion of total lipid extracts to fatty acid methyl esters using both catalysts. Additionally, GLC analysis confirmed similar (P = 0.96) total fatty acid concentrations for both catalysts. Concentrations of most identified fatty acids (13:0, 14:0, 16:0, 16:1, 17:0, 17:1, 18:0, 18:1, 18:2, 18:3, 19:0, 20:0, 20:1, 22:0, 22:1, 22:3, 24:0, 24:1, and 28:0) were similar (P = 0.17 to 0.99) for both catalysts. Concentrations of 14:0 tended to be greater (P = 0.07) for HCl but weight percentages of 14:0 did not differ (P = 0.23) between catalysts. Concentrations and weight percentages of 17:1 were less (P < 0.0001) for HCl compared with BF3. Boron-trifluoride may cause partial isomerization of predominant fatty acids because the concentrations of unidentified fatty acids with GLC retention times of 8.0, 13.9, and 31.9 min were greater (P = 0.005 to 0.05) for BF3; whereas, only the concentration of unidentified fatty acid eluding at 14.8 min was greater (P = 0.02) for HCl. Nevertheless, total concentration of unidentified fatty acids did not differ (P = 0.71) between catalysts. Additionally, total weight percentages of identified fatty acids and unidentified fatty acids were not affected (P = 0.37) by catalyst (91.2 and 8.8% vs. 90.6 and 9.4% for HCl and BF3, respectively). It is also possible that BF3 is more efficient at catalyzing methylation of less common or unusual fatty acids, but BF3 costs $0.19 per sample more than HCl. We conclude that 1.09 M methanolic HCl is both a cost effective and appropriate substitute for 14% BF3 in methanol for preparation of fatty acid methyl esters from freeze-dried forage samples.
منابع مشابه
بررسی ترکیب شیمیایی، الگوی اسیدهای چرب، فعالیت آنتی اکسیدانی و تولید گاز بقایای انار به روش برونتنی
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