	US 11,921,122 B2
	Methods for detecting vitamin D metabolites by mass spectrometry
Nigel J. Clarke, Vista, CA (US); Brett Holmquist, Mission Viejo, CA (US); Gloria Kwang-Ja Lee, Irvine, CA (US); and Richard E. Reitz, Las Vegas, NV (US)
Assigned to Quest Diagnostics Investments Incorporated, Wilmington, DE (US)
Filed by Quest Diagnostics Investments Incorporated, Wilmington, DE (US)
Filed on Feb. 9, 2023, as Appl. No. 18/107,947.
Application 18/107,947 is a continuation of application No. 17/188,969, filed on Mar. 1, 2021, granted, now 11,579,154, issued on Feb. 14, 2023.
Application 17/188,969 is a continuation of application No. 16/390,989, filed on Apr. 22, 2019, granted, now 10,935,558, issued on Mar. 2, 2021.
Application 16/390,989 is a continuation of application No. 15/848,325, filed on Dec. 20, 2017, granted, now 10,267,810, issued on Apr. 23, 2019.
Application 15/848,325 is a continuation of application No. 15/388,844, filed on Dec. 22, 2016, granted, now 9,880,180, issued on Jan. 30, 2018.
Application 15/388,844 is a continuation of application No. 15/005,801, filed on Jan. 25, 2016, granted, now 9,529,004, issued on Dec. 27, 2016.
Application 15/005,801 is a continuation of application No. 14/180,722, filed on Feb. 14, 2014, granted, now 9,244,084, issued on Jan. 26, 2016.
Application 14/180,722 is a continuation of application No. 13/871,457, filed on Apr. 26, 2013, granted, now 8,936,943, issued on Jan. 20, 2015.
Application 13/871,457 is a continuation of application No. 13/327,650, filed on Dec. 15, 2011, granted, now 8,431,411, issued on Apr. 30, 2013.
Application 13/327,650 is a continuation of application No. 13/115,916, filed on May 25, 2011, granted, now 8,101,427, issued on Jan. 24, 2012.
Application 13/115,916 is a continuation of application No. 11/386,215, filed on Mar. 21, 2006, granted, now 7,972,867, issued on Jul. 5, 2011.
Application 11/386,215 is a continuation in part of application No. 11/101,166, filed on Apr. 6, 2005, granted, now 7,745,226, issued on Jun. 29, 2010.
Prior Publication US 2023/0184790 A1, Jun. 15, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. G01N 33/82 (2006.01); G01N 30/72 (2006.01); G01N 30/88 (2006.01); H01J 49/00 (2006.01)

CPC G01N 33/82 (2013.01) [G01N 30/7233 (2013.01); G01N 30/72 (2013.01); G01N 2030/8813 (2013.01); G01N 2030/8822 (2013.01); G01N 2458/15 (2013.01); G01N 2560/00 (2013.01); H01J 49/00 (2013.01); H01J 49/004 (2013.01); Y10T 436/20 (2015.01); Y10T 436/203332 (2015.01); Y10T 436/24 (2015.01)]

4 Claims

1. A method for determining an amount of 25-hydroxyvitamin D₃or 25-hydroxyvitamin Dain a sample by tandem mass spectrometry, the method comprising:

(a) adding an internal standard to a first sample containing 25-hydroxyvitamin D₃or 25-hydroxyvitamin D₂to form a second sample;

(b) purifying the second sample by liquid chromatography;

(c) ionizing said 25-hydroxyvitamin D₃or 25-hydroxyvitamin D₂and 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 D₃or 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 D₃or 25-hydroxyvitamin Dain said sample from the amount of the one or more of said fragment ions.