Use of a Dual Coulometric-Amperometric Detection Cell Approach in Thyroid Hormone Assay

Investigations into lactoperoxidase-catalysed bromination of tyrosine and thyroglobulin

Thyroid peroxidase and lactoperoxidase are capable of producing oxidized bromine species. Thus investigations into bromination reactions with tyrosine and thyroglobulin were undertaken in order to gain insight into possible formation of brominated thyroid hormone analogues. A reversed-phase high-performance liquid chromatographic method was developed for the separation of bromine/iodine-substituted tyrosines and used as a basis for these investigations combined with ultraviolet absorption and electrochemical detection. The results indicate that in vivo bromination of tyrosyl residues in thyroglobulin might be of some importance in cases of either iodine deficiency or excessive bromide intake.

Separation and detection of closely related endorphins by liquid chromatography-electrochemistry

The specific aim of this study was to investigate the selectivity of liquid chromatography--electrochemistry for minor variations in the structure of small endorphins. Using isocratic mobile phases, chromatographic conditions were established for the separation of a series of closely related endorphins. Hydrodynamic voltammetry showed that each peptide exhibited a characteristic oxidative behavior that was also reflected in peak current ratios. Changes in a small moiety altered both the chromatographic behavior and electroactivity of these neuropeptides.