Quantification of the 3α and 3β epimers of 25-hydroxyvitamin D3 in dried blood spots by LC-MS/MS using artificial whole blood calibration and chemical derivatization
3α- and 3β-25-hydroxyvitamin D3 epimers were quantified from dried blood spots using LC-MS/MS. The assay was based on newly developed artificial vitamin D-free whole blood matrix. The calibration routine improved analytical performance over existing techniques. The method was compared across 3 different assay platforms with serum and whole blood.