Patent ID: 8293540

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: purifying 1α,25-dihydroxyvitamin D 2 (1α,25(OH) 2 D 2 ) from the sample via one or more purification steps; ionizing purified 1α,25(OH) 2 D 2 without subjecting said purified 1α,25(OH) 2 D 2 to conditions suitable to dehydrate said 1α,25(OH) 2 D 2 prior to ionizing to generate one or more 1α,25(OH) 2 D 2 ions detectable by mass spectrometry; 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; 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 375.1±0.5, 157.0±0.5, and 105.3±0.5.