Online ISSN : 1348-3315
Print ISSN : 1342-8284
ISSN-L : 1342-8284
Sensitive Analysis of Triiodothyronine in Serum by One-Step Multiple Methylations Followed by LC/ESI-MS/MS
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JOURNAL FREE ACCESS Advance online publication

Article ID: 2024.004


Quantification of the circulating thyroid hormones helps in the diagnosis and evaluation of therapy efficacy for thyroid diseases. When only a small volume of serum/plasma can be used, the quantification of triiodothyronine (T3), an active thyroid hormone, is no easy task due to its low concentration. In this study, a procedure enabling the multiple methylations of T3 in one step was developed to enhance its detectability during electrospray ionization (ESI)-tandem mass spectrometry (MS/MS). The combined use of trimethylsilyldiazomethane and iodomethane provided the quaternized derivative, which was completely methylated in the carboxy, phenolic hydroxy and amino groups in T3, within 60 min. This derivative demonstrated a higher ESI efficiency due to the permanent positive charge and a good fragmentation behavior during MS/MS to produce a product ion containing the T3-specific moiety. When this methylation procedure was applied to the serum analysis by liquid chromatography (LC)/ESI-MS/MS, T3 was detected with a sufficient signal-to-noise ratio (S/N) using only a 20-μL serum aliquot. The S/N-based sensitivity was increased four-fold by the multiple methylations in the serum assay. Thus, the developed procedure satisfactorily worked for the trace analysis of the serum T3 by LC/ESI-MS/MS.

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