Simultaneous quantitative analysis of nine vitamin D compounds in human blood using LC-MS/MS

Aim: It has been suggested that each member of the family of vitamin D compounds may have different function(s). Therefore, selective quantification of each compound is important in clinical research. Materials & methods: Development and validation attempts of a simultaneous determination method of 12 vitamin D compounds in human blood using precolumn derivatization followed by LC-MS/MS is described. Internal standard calibration with 12 stable isotope labeled analogs was used to correct for matrix effects in MS detector. Results & conclusion: Nine vitamin D compounds were quantifiable in blood samples with detection limits within femtomole levels. Serum (compared with plasma) was found to be a more suitable sample type, and protein precipitation (compared with saponification) a more effective extraction method for vitamin D assay.