Development and Certification of a Standard Reference Material for Vitamin D Metabolites in Human Serum

The National Institute of Standards and Technology (NIST), in collaboration with the National Institutes of Health’s Office of Dietary Supplements (NIH-ODS), has developed a Standard Reference Material (SRM) for the determination of 25-hydroxyvitamin D [25­(OH)­D] in serum. SRM 972 Vitamin D in Human Serum consists of four serum pools with different levels of vitamin D metabolites and has certified and reference values for 25­(OH)­D₂, 25­(OH)­D₃, and 3-epi-25­(OH)­D₃. Value assignment of this SRM was accomplished using a combination of three isotope-dilution mass spectrometry approaches, with measurements performed at NIST and at the Centers for Disease Control and Prevention (CDC). Chromatographic resolution of the 3-epimer of 25­(OH)­D₃ proved to be essential for accurate determination of the metabolites