Development and validation of a method for determination of plasma 25-hydroxyvitamin D3 3-sulfate using liquid chromatography/tandem mass spectrometry.

The quantification of plasma 25-hydroxyvitamin D3 3-sulfate [25(OH)D3S] is expected to be helpful in the assessment of the vitamin D status, especially for infants. In this study, a simple and sensitive method for the quantification of 25(OH)D3S in plasma using liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has been developed and validated. The plasma was deproteinized with acetonitrile, purified using an Oasis(®) HLB cartridge, and subjected to LC/ESI-MS/MS operating in the negative-ion mode. Quantification was based on the selected reaction monitoring, and deuterated 25(OH)D3S was used as the internal standard. This method enabled the reproducible (intra- and inter-assay relative standard deviations, 7.9% or lower) and accurate (analytical recovery, 95.8-105.3%) quantification of the plasma 25(OH)D3S using a 20-μL sample, and the limit of quantification was 2.5ng/mL. The developed method was applied to the determination of plasma 25(OH)D3S in infants; the result revealed that preterm infants have lower plasma 25(OH)D3S concentrations.