Partition affinity ligand assay (PALA) for quantitation of triiodothyronine in serum

Radioimmunoassay of triiodothyronine was performed with a homogeneous incubation system. Bound and free ligand were separated by partitioning in an aqueous two-phase system. The agreement between the results obtained with this technique and conventional heterogeneous radioimmunoassay was very good (r = 0.981).