Abstract
The usefulness and capabilities of gradient elution techniques with electrochemical detection are shown with a rapid separation of D,L-tyrosine (Tyr), 3-iodo-L-tyrosine (MIT), 3,5-diiodo-L-tyrosine (DIT), D,L-thyronine (T0), 3,5-diiodo-D,L-thyronine (T2), 3,3′,5-triiodo-L-thyronine (T3), and L-thyroxine (T4) by reverse phase liquid chromatography. A rapid (five minute) isocratic separation of T0, T2, T3, and T4 is also reported. Limits of detection are in the sub-nanogram range with a linear dynamic range to 500 ng for T2 and T3, and 1000 ng for T4. Analysis of levothyroxine sodium tablets and injectable intravenous samples is described.