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Stable isotope-dilution liquid chromatography/tandem mass spectrometry method for determination of thyroxine in
Tatsuya Higashi1, Takuya Ichikawa, Chikara Shimizu
1Laboratory of Analytical and Bioanalytical Chemistry, School of Pharmaceutical Sciences and Global COE Program, University of Shizuoka, Suruga-ku, Shizuoka, Japan. higashi@u-shizuoka-ken.ac.jp
Abstract:
A liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) method for the determination of thyroxine (T(4)) in human saliva has been developed and validated. The saliva was deproteinized with methanol, purified using a Strata-X™ cartridge, and subjected to LC/ESI-MS/MS. Quantification was based on selected reaction monitoring, and [(13)C(6)]-T(4) was used as the internal standard. This method allowed the reproducible (intra- and inter-assay relative standard deviations, <4.8%) and accurate (analytical recovery, 96.5-99.6%) quantification of the salivary T(4) using a 400 μl sample, and the limit of quantification was 25.0 pg/ml. A preliminary study using the developed method found that there is a diagnosable difference in the salivary T(4) concentration between the euthyroid subjects and the patients with Graves disease.
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