IMPROVED ULTRAFILTRATION METHOD FOR FREE-THYROXINE AND TRIIODOTHYRONINE IN SERUM

  • 1 January 1980
    • journal article
    • research article
    • Vol. 26  (1) , 159-162
Abstract
An ultrafiltration technique is described for rapidly and directly determining free triiodothyronine or free thyroxine, or both. After equilibrating serum at 37.degree. C with purified tracer of high specific activity, 0.15 ml of serum is placed in 2.8 ml of phosphate buffer (0.1 mol/l, pH 7.4) in the ultrafiltration cell and successive 0.2- and 0.6-ml fractions of protein-free ultrafiltrate are obtained. Under the conditions free ligand concentration was independent of flow rate. After purifying the 2nd fraction with protein-coated charcoal, the proportion of free triiodothyronine or free thyroxine was determined. Samples from normal adult men and women, including women who were taking oral contraceptives or were pregnant, and from hypo- and hyperthyroid patients gave results that agreed with those obtained by equilibrium dialysis. Speed is the main advantage of the method: 1 technologist can complete the procedure in 2 h and, using a multi-micro-ultrafiltration system, can process many samples in 1 day. For laboratories where index-type reactions are performed routinely and direct free triiodothyronine or free thyroxine is determined only on selected specimens, this method is superior to dialysis. It is also very convenient for rapidly purifying tracers, to at least 97% radiochemical purity, with 94% recovery and no dilution.

This publication has 1 reference indexed in Scilit: