Patent ID: 11921122
Assignee: QUEST DIAGNOSTICS INVESTMENTS INCORPORATED
Field: Measurement (Instruments)
Classification: CPC G  H  Y | IPC G  H

Claim 0:
1. A method for determining an amount of 25-hydroxyvitamin D3 or 25-hydroxyvitamin Dain a sample by tandem mass spectrometry, the method comprising:
(a) adding an internal standard to a first sample containing 25-hydroxyvitamin D3 or 25-hydroxyvitamin D2 to form a second sample;
(b) purifying the second sample by liquid chromatography;
(c) ionizing said 25-hydroxyvitamin D3 or 25-hydroxyvitamin D2 and the internal standard by atmospheric pressure chemical ionization (APCI) in positive ion mode to form a precursor ion comprising an ion having a mass to charge ratio of 383.16+−0.5 for 25-hydroxyvitamin D3 or 395.30+−0.5 for 25-hydroxyvitamin D2;
(d) generating one or more fragment ions of said precursor ion; and
(e) determining an amount of the one or more fragment ions generated in step (d); and
(f) determining the amount of 25-hydroxyvitamin D3 or 25-hydroxyvitamin Dain said sample from the amount of the one or more of said fragment ions.