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Dep. of Animal Sci., Univ. of Wyoming, Laramie, WY 82071; J.D. Derner, USDA-ARS, High Plains Grasslands Research Center, Cheyenne, WY 82009
* Corresponding author (brethess{at}uwyo.edu).
Preparation of fatty acid methyl esters from forages comparing methanolic boron-trifluoride (BF3) to methanolic hydrochloric acid (HCl) as a catalyst in single-step direct transesterification has not been reported. Our objective was to compare 1.09 M methanolic HCl to 1.03 M (7%) methanolic BF3 as catalysts for direct transesterification of fatty acids in freeze-dried forage samples. Thin-layer chromatographic analysis revealed complete conversion of total lipid extracts to fatty acid methyl esters using both catalysts. Additionally, gas–liquid chromatography analysis confirmed similar (P = 0.95) total fatty acid concentrations for both catalysts. Regression analysis indicated that similar values for total concentration would be obtained (P < 0.0001; r2 = 0.96; slope = 0.98 ± 0.03) between the two catalysts. Concentrations of most individual fatty acids were similar (P = 0.17–0.99) for both catalysts. Summed weight percentages of identified fatty acids, as well as sum of unidentified peaks, were not affected (P = 0.27) by catalyst (91.8 and 8.7% vs. 90.8 and 9.2% for HCl and BF3, respectively). We conclude that 1.09 M methanolic HCl is an appropriate substitute for 1.03 M methanolic BF3 for preparation of fatty acid methyl esters from freeze-dried forage samples. This result is of interest because HCL is both less costly and less caustic than BF3.
Abbreviations: GLC, gas-liquid chromatography
Received for publication July 5, 2007.
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