Value Assignment of Vitamin D and 25-Hydroxyvitamin D in Food-Matrix Standard Reference Materials (SRMs) Using Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry (ID LC-MS/MS).

Discrepancies exist between reported vitamin D dietary intake and measured status. Hydroxylated metabolites such as 25-hydroxyvitamin D [25(OH)D] may be more bioavailable; however, information on 25(OH)D content in foods is limited. To address this gap and support analytical method validation, NIST value assigned vitamin D2, vitamin D3, and 25-hydroxyvitamin D3 [25(OH)D3] in five food-matrix Standard Reference Materials® (SRMs). Using isotope dilution LC-MS/MS, values were established for SRMs 1546a (Meat Homogenate), 1549a (Whole Milk Powder), 1577c (Bovine Liver), 1845a (Whole Egg Powder), and 3235 (Soy Milk). Mass fractions ranged from 0.498 μg/kg to 49.5 μg/kg for vitamin D3 and 0.53 μg/kg to 12.1 μg/kg for 25(OH)D3. These SRMs enable validation of analytical methods and measurement comparability assessment across laboratories. By providing accurate reference values for both parent vitamins and metabolites, these materials support a better understanding of the relationship between dietary intake and overall nutritional status.