Modification of the method for vitamin A in foods and feeds for use with margarine and butter: collaborative study

An adaptation of the method for vitamin A in feeds and foods to margarine and butter was studied in 1977 and 1978. The principal change was the use of 2 extractions with an ether-hexane mixture instead of one with hexane. Results of the 1977 test were not good enough to recommend adoption. The 1978 analytical samples consisted of 4 margarines, including a known, and a butter. Data were reported by 11 analysts. Averages for vitamin A (microgram/g) and coefficients of variation (%) were, respectively: A (known)--7.2, 5.7; 1--8.2, 11.1; 2--11.4, 3.9; 3--7.6, 10.7; butter--8.5, 13.3; and for carotene: A--5.6, 6.4; 1--6.0, 5.5; 2--0; 3--5.8, 3.8; butter--3.1, 11.8. Carotene results were grouped reasonably closely and tended to be distributed randomly, but vitamin A results had a less random trend. Trifluoroacetic acid was studied as an alternative colorimetric reagent for determining vitamin A, with overall satisfactory results. The modification for determining vitamin A and carotene in butter and margarine, and the use of trifluoroacetic acid as an alternative colorimetric reagent have been adopted as official first action.