THE DETERMINATION OF VITAMIN A AND CAROTENE IN SMALL QUANTITIES OF BLOOD SERUM

Abstract

A method was devised for making rapid, routine estimations of carotene and vitamin A with from 35 to 60 c.mm, blood serum. The serum was obtained from a finger prick, and was heated in a narrow tube with alcoholic potash. The digest was then extracted with a mixture of kerosene and xylene of low volatility. During the extraction the tube was agitated by holding it against a slightly flattened, rotating nail, or alternatively a piece of stainless steel wire was introduced and the tube shaken by hand. The hydrocarbon layer was transferred to the specially narrow cuvette of a Beekman spectrophotometer, and readings were made at 460 and 328 mµ. The solution was next transferred to a short soft glass tube, and vitamin A was destroyed by ultraviolet irradiation. A further reading at 328 m/i. was then taken, and the amount of vitamin A was calculated from the difference between the first and second readings. In a series of 11 specimens of serum, values of 39 to 106 µg. per 100 ml., with a mean of 58 µg., were found for vitamin A by the micromethod, while the carotene contents were 89 to 198 µg., mean 141 µg. By a macromethod requiring 7 ml. of serum, and employing the SbC13 reaction, values of 45 to 111 µg. mean 59 µg. were found for vitamin A, and of 83 to 232 µg. mean 139 µg., for carotene. Special racks and other conveniences are described which enable several steps in the micro-method to be carried out simultaneously on a large number of specimens.-T. Moore.