ABSTRACT
The official GLC method of the Association of Official Analytical Chemists (AOAC) for determining vitamin E was modified and collaboratively studied for the National Formulary (NF). The internal standard hexadecyl hexadecanoate (cetyl palmitate) was substituted for the dotriacontane used in the AOAC method, and some other minor changes were made. Eleven samples, representing all types of NF formulations and NF bulk materials, were analyzed by 11 laboratories. The coefficients of variation of the reproducibility and repeatability were 4.5 and 2.4%, respectively, for all laboratories and samples. The values were 3.4 and 1.6%, respectively, when the one laboratory statistically determined to be an outlier was excluded. The coefficients of variation of reproducibility and repeatability for alpha-tocopheryl acid succinate were 2.1 and 1.5%, respectively. All of these values lie within the 5% limit required by the NF.
Subject(s)
Vitamin E/analysis , Analysis of Variance , Chromatography, Gas , Evaluation Studies as Topic , MethodsABSTRACT
A gas-liquid chromatographic (GLC) method, using the butyryl esters of sterols, has been developed for the measurement of cholesterol, stigmasterol, sitosterol, and campesterol in foods. An immobile phase of 1% SE-30 coated on 100-120 mesh Gas-Chrom Q packed in a 6 inch X 4 mm id glass column operated at 255 degrees C was the most satisfactory of 7 column packings evaluated. Extraction with chloroform-methanol gave 98.7% recovery with a coefficient of variation of 1.8% for cholesterol added to a variety of foods. When cholesteryl palmitate was added to vegetable oil and the butyryl derivative was prepared, followed by GLC analysis, the recovery was 99.3% with a coefficient of variation of 0.9%. Amounts as low as 1 mg/100 g food can be detected with a precision of 2.5%. The results of the analysis of a variety of foods for cholesterol, campesterol, sitosterol, and stigmasterol are given.
