Detection and Quantification of 3,5,3′-Triiodothyronine and 3,3′,5′-Triiodothyronine by Electrospray Ionization Tandem Mass Spectrometry

A novel and rapid method for identifying and quantifying 3,5,3′-triiodothyronine (T3) and 3,3′,5′-triiodothyronine (rT3; reverse T3) has been introduced using electrospray ionization tandem mass spectrometry (ESI-MS/MS). MS2 spectra in either negative ionization mode or positive ionization mode can be used to differentiate T3 and rT3. Quantification of the T3 and rT3 isomers under the negative ionization mode is also achieved without prior separation by HPLC.