Determination of Cholesterol in Egg Yolk by High Performance TLC with Densitometry

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Abstract
A simple quantitative TLC determination of cholesterol in egg yolk is described. Cholesterol in the yolk is extracted with chloroform-methanol (2:1) and the extract filtered through glass wool. After dilution to a known volume, samples and standards are developed on a high performance preadsorbent silica gel layer, cholesterol is detected with cupric acetate-H3-PO4 reagent, and zones are scanned and compared. Precision of the method, evaluated by replicate analyses, was 2.2%, and recovery from a sample spiked at a concentration level of 14.3 mg/g was 104%. Analysis of 20 eggs gave cholesterol values ranging from 9.7–26.2 mg/g, and the method was also applied to butter and cream samples. Because of the selectivity of the TLC method, lower results were obtained compared to a standard colorimetric assay. Fractions representing sterols, diacylglycerols, triacylglycerols, stearyl esters, and hydrocarbons were identified from egg yolk, and the sterol fraction was found to contain only cholesterol by argentation- and RP-TLC and capillary GC.

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