Semiautomatic method for the separation and determination of total triiodothyronine and thyroxine in serum.

A semiautomatic procedure is presented for the separate determination of total T3 and T4 in serum in approximately 10 hrs simultaneously in 25 samples. Removal of the thyroid hormones from the serum, separation of T3 from T4 and concentration of the peaks were achieved in a closed system, consisting of three consecutive columns. The automatic microchemical iodine determination of T3 and T4 respectively, had a sensivity of less than 0.5 ng. Recovery for T3 was 87% and for T4 88%. High accuracy and reproducibility could be shown with pooled control scrum. The overspill of T4 into T3 was less than 0.1% of total T4. The means of total scrum T8 and T4 were 1.46 ± 0.20 (S. D.) //g/1 and 76.5 ± 10.7 ^g/1 respectively for euthyroid controls. In patients with nontoxic goiter the T4 levels were significantly lower than in euthyroid controls, whereas the T3 levels and the T3:T., ratio were significantly higher.