Patent ID: 8034627

Claim:
A method for determining the amount of 1α,25-dihydroxyvitamin D 2 (1α,25(OH) 2 D 2 ) in a sample by mass spectrometry, the method comprising the steps of: ionizing 1α,25(OH) 2 D 2 from the sample to generate one or more 1α,25(OH) 2 D 2 ions detectable by mass spectrometry, wherein said one or more 1α,25(OH) 2 D 2 ions comprise one or more ions selected from the group consisting of ions with a mass-to-charge ratio of 393.1±0.5 and 225.0±0.5; determining the amount of one or more of the 1α,25(OH) 2 D 2 ions by mass spectrometry; and relating the determined amount of 1α,25(OH) 2 D 2 ions to the amount of 1α,25(OH) 2 D 2 in the sample.