Analysis of Fat-Soluble Vitamins. XVIII. Interlaboratory Comparison of Vitamin D Assay Methods

Abstract

Nine laboratories determined the vitamin D3 content of 4 samples in oil containing, in addition to vitamin D3, different amounts of tachysterol3, isotachysterol3, trans-vitamin D3, lumisterol3, and 7-dehydrocholesterol, in order to assess the effect of these isomers on the assay. The analyst selected the method to be used. Three high performance liquid chromatographic (HPLC) methods were applied: 2 were direct and the third required prior isolation of the unsaponifiable material. The 6 remaining analysts used gas-liquid chromatographic (CLC) methods; all GLC techniques required saponification and silylation, and 3 required an additional pretreatment. The results from the GLC and HPLC methods were compared with the known composition of the samples and the results obtained by the official AOAC method, 43.B14–43.B24. The samples were also analyzed by the AOAC method without the maleic anhydride reaction and by the AOAC method with correction for the isotachysterol content. The results of the HPLC assays showed that this technique is promising, but improvements are still needed. The precision and accuracy of the GLC assays varied. However, satisfactory results were obtained after extensive prepurifications. The AOAC chemical method was satisfactory for those samples shown suitable by the confirmation test, i.e., in the absence of isotachysterol.

Comprehensive analysis of vitamin D3 impurities in oily drug products using supercritical fluid chromatography–mass spectrometry

“…Very few papers described the analysis of these compounds. The isobaric impurities have been mainly studied qualitatively in the context of degradation studies or to ensure method selectivity in the determination of vitamin D3 11,[13][14][15][16][17][18] . Because it is an analogue to vitamin D, some studies have described the determination of dihydrotachysterol in biological matrices to determine the antirachitic activity, its metabolization and/or bioavailability 19,20 .…”

“…The isobaric impurities have been mainly studied qualitatively in the context of degradation studies or to ensure method selectivity in the determination of vitamin D 3 . 11,[13][14][15][16][17][18] Because it is an analog to vitamin D, some studies have described the determination of dihydrotachysterol in biological matrices to determine the antirachitic activity, its metabolization, and/or bioavailability. 19,20 For octanoate and decanoate ester impurities, Ballard et al 12 described their detection in a degradation study of an experimental tablet formulation.…”