15C-3 |
HPLC method development for separation of grain sorghum wax classes |
K. T. HWANG, Department of Food Science and Human Nutrition, Chonbuk National University, Chonju, Chonbuk, 561-756, South Korea, S. L. Cuppett, Department of Food Science and Technology, University of Nebraska, Lincoln, NE 68583-0919, C. L. Weller, Department of Biological Systems Engineering, University of Nebraska, Lincoln, NE 68583-0726, and M. A. Hanna, Industrial Agricultural Products Center, University of Nebraska, Lincoln, NE 68583-0730. Development of methods for analysis of waxes by HPLC has been slow. Grain sorghum wax is composed of large amounts of fatty aldehydes, fatty alcohols, and fatty acids with minor components such as hydrocarbons, wax esters (WE), and steryl esters (SE). In most HPLC systems developed for analyses of non-polar lipids, aldehydes, WE, and SE in sorghum wax coelute. Separation of WE and SE from each other has been studied for limited samples. However, separation of the two components from aldehydes using HPLC has not been studied. This study was performed to affect the separation of WE, SE, and fatty aldehydes for quantification of the major components in grain sorghum wax using HPLC with a silica column and an evaporative light scattering detector (ELSD). HPLC was run in gradient modes or in isocratic modes, using mixtures of hexane, methyl tert-butyl ether (MTBE), and acetic acid as mobile systems. Column was a silica column. The column was heated at 40 degrees C. Exposed lines were maintained at about 38-40 degrees C. Detector was an ELSD operated at 50 degrees C with nitrogen pressure of 930 kPa. Gradient modes using 0.2% (v/v) acetic acid and 0.02% MTBE in hexane and 0.2% acetic acid in MTBE or hexane and 0.2% acetic acid in MTBE separated aldehydes, acids and alcohols, as well as WE, SE, triacylglycerols (TG), and free sterols. Isocratic modes using 0.1% (v/v) acetic acid and 0.02% MTBE in hexane or 0.04% acetic acid and 0.01% MTBE in hexane separated individual WE and SE. Grain sorghum wax was composed of 46.3% (w/w) fatty aldehydes, 7.5% fatty acids, 41.0% fatty alcohols, 0.7% hydrocarbons, 1.5% WE and SE, and 0.9% TG, based on HPLC data. HPLC methods developed in this study can accurately determine major and minor components in waxes including grain sorghum wax.
Session 15C, Food Chemistry: Food composition and analysis
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