Spectrophotometric Study of a New Colorimetric Reaction of Vitamin A

Vitamin A in Fish Oils

“…Glycerol 1,3-Dichlorohydrin Method. Modifications of Sobel and Werbin (29,30) procedures were necessary to use the Evelyn photolectric colorimeter to measure color intensities.…”

“…As the Evelyn photoelectric colorimeter has been widely and satisfactorily used in connection with the antimony trichloride method (4), it seemed to be the logical instrument for use in the present studies. However, certain modifications of the original procedure were found necessary (29,30) especially with respect to the amount of reagent used, because the macro system of the Evelyn requires a minimum of 6 ml. of solution.…”

“…The color produced by the reaction of the activated glycerol 1,3dichlorohydrin with vitamin A has been reported (29,30) to remain stable for at least 8 minutes after development of maximum intensity. In this laboratory, however, the maximum intensity of the colors produced by the reaction of either the authors' own activated reagent, or the commercial activated reagent with vitamin A acetate, developed approximately 2 minutes after the mixing of the reagents with the sample, remained essentially stable for 3 additional minutes, and then declined in intensity.…”

“…The stability of the color did not appear to be influenced by the two ratios or reagents to samples nor by the type of instrument used in making the color measurements. Sobel and Werbin (29,30) suggested the use of a constant temperature bath of 25 °C. as a means of bringing about uniform color development.…”

Determination of Vitamin A in Fish Liver Oils with Activated Glycerol Dichlorohydrin

“…Since agreement between activated glycerol dichlorohydrin and antimony trichloride methods is close, the authors propose activated glycerol dichlorohydrin for estimating vitamin Ain fish liver oils. RECENTLY the authors reported a new colorimetric reaction of vitamin A which takes place on the addition of practical (8) or activated (7) glycerol dichlorohydrin to a solution of vitamin A in chloroform. This new reaction appears suitable for quantitative purposes, as it obeys Beer's law over a reasonable range and offers the following advantages over the widely used Carr-Price reaction: (1) The violet color produced is stable from 2 to 10 minutes after the addition of the reagent, (2) the reagent• is not affected by traces of moisture that occur on the most humid days, (3) no film of antimony oxychloride is left on the cuvettes, (4) the reagent is practically noncorrosive, and (5) it is possible to use a photoelectric spectrophotometer (Beckman) in measuring the absorption of the violet color.…”