Selection of a surrogate matrix for the quantification of an endogenous analyte in dried whole blood.

Aim: A surrogate matrix is needed to quantify 25-hydroxyvitamin D3 in dried whole blood (DWB). To date, there has been limited guidance on approaches for quantification of endogenous analytes in atypical matrices, such as DWB. Methods: Different surrogate matrices were investigated in a systematic process using an LC-MS/MS assay. Performance assessment was made using quality controls of DWB with different hematocrits. Results & conclusion: Suitability of both phosphate-buffered saline containing bovine serum albumin and washed red blood cells recombined with phosphate-buffered saline containing bovine serum albumin as a surrogate matrix was demonstrated across a range of concentrations and hematocrits representative of expected endogenous analyte samples.