TY - JOUR T1 - Isotope dilution ultra performance liquid chromatography-tandem mass spectrometry method for simultaneous measurement of 25-hydroxyvitamin D2, 25-hydroxyvitamin D3 and 3-epi-25-hydroxyvitamin D3 in human serum. AU - Schleicher,Rosemary L, AU - Encisco,Sara E, AU - Chaudhary-Webb,Madhulika, AU - Paliakov,Ekaterina, AU - McCoy,Leslie F, AU - Pfeiffer,Christine M, Y1 - 2011/05/13/ PY - 2011/03/17/received PY - 2011/05/04/revised PY - 2011/05/05/accepted PY - 2011/5/24/entrez PY - 2011/5/24/pubmed PY - 2011/10/19/medline SP - 1594 EP - 9 JF - Clinica chimica acta; international journal of clinical chemistry JO - Clin Chim Acta VL - 412 IS - 17-18 N2 - BACKGROUND: An ultra performance liquid chromatography-tandem mass spectrometry method with calibration traceable to NIST SRM was developed and validated to measure concentrations of 25-hydroxyvitamin D(2) (25OHD(2)), 25-hydroxyvitamin D(3) (25OHD(3)) and the C-3 epimer of 25OHD(3) (epi-25OHD(3)) in human serum. METHODS: Tri- and hexa-deuterated internal standards were added to serum (100 μl) to monitor recovery. Liquid-liquid extraction was used to extract the hexane-soluble materials. Calibration solutions [8-100 nmol/L 25OHD(2,) 12-150 nmol/L 25OHD(3), and 4-50 nmol/L epi-25OHD(3)] prepared in phosphate-buffered saline containing 4% albumin were similarly processed. Using a pentafluorophenyl column (2.1×100 mm) and isocratic methanol/water (72/28, v/v) flowing at 0.4 ml/min, run time was 14 min per sample; 25OHD(3) and epi-25OHD(3) were baseline separated. Atmospheric pressure chemical ionization in the positive ion mode with selected reaction monitoring captured the following transitions: 25OHD(2), m/z 395.3>377.3 (209.1 qualifier); (epi-)25OHD(3), m/z 383.3>365.3 (105.1 qualifier); d(3)-25OHD(2), m/z 398.3>380.3; and d(6)-25OHD(3), m/z 389.3>371.3. RESULTS: Recovery averaged ≥98%. Total imprecision was ≤10% when concentrations were ≥20 nmol/l. Bias averaged <5%. Detection limits were <5 nmol/l. Median (nmol/l) 25OHD(2), 25OHD(3) and epi-25OHD(3) were quantitated in 98 blood donors (<LOD, 56.0, <LOD) and 35 pregnant women (<LOD, 87.6, 3.70). CONCLUSIONS: This method is highly accurate, precise and specific. SN - 1873-3492 UR - https://www.unboundmedicine.com/medline/citation/21601563/Isotope_dilution_ultra_performance_liquid_chromatography_tandem_mass_spectrometry_method_for_simultaneous_measurement_of_25_hydroxyvitamin_D2_25_hydroxyvitamin_D3_and_3_epi_25_hydroxyvitamin_D3_in_human_serum_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0009-8981(11)00266-X DB - PRIME DP - Unbound Medicine ER -