Application of orthogonal functions to the spectrophotometric determination of calciferol in oily injections.

The method of orthogonal functions has been applied to the rapid spectrophotometric determination of vitamin D in oily injections. The method involves saponification of the sample and extraction of the unsaponifiable matter with ether. After cautious evaporation of ether, the residue is dissolved in isopropanol and the absorbance of the solution is measured in the range 246--296 nm at 10 nm intervals. For BPC injections, the saponification step may be omitted. A suitable dilution of the sample in isopropanol is measured in the range 250.5--300.5 nm at 10 nm intervals. Accurate and precise results are obtained in both cases.