Abstract
Keverling Buisman at al. (J. Pharm. Sci. 57,1326,1968) proposed that the total value of vitamin D_2 and previtamin D_2 should be always estimated for evaluation of the potential vitamin D_2 because of the rapid thermal isomerization of vitamin D_2 into previtamin D_2. Quantitative thin-layer chromatography was investigated to establish a routine method for the determination of potential vitamin D_2 in ultraviolet irradiated solution of ergosterol and the following method was proposed. A sample solution in ethylene dichloride was refluxed for 1.5 hours to obtain the equilibrium of vitamin D_2 and previtamin D_2 and then subjected to the quantitative thinlayer chromatography. Influence of tachysterol_2 accompanied with vitamin D_2 fraction was eliminated by maleic anhydride reaction at room temperature according to Mulder et al. (Pharm. Weekblad 50,1457,1965). After estimating the vitamin D_2 value by Nield color reaction, it was multiplied 1.56 as the conversion factor (induced from experimental results) to convert into the total value of potential vitamin D_2 (D_2 and pre D_2).
