Study of the Factors Affecting the Precision and Accuracy of Thyroxine (T4) Determinations

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Abstract
Factors affecting the precision and accuracy of the chromatographic and analytical schemes for determination of serum T4 levels by column chromatography and bromination of the column eluates have been studied. The factors which affect chromatography include reagent constitution and concentration, resin mesh size, and number, volume, and types of washes employed. In the analytical scheme, the factors that influence precision and accuracy of the automated analysis of the column eluates are type of manifold used, duration and temperature of reactant incubation, effects of chloride ion concentration and pH on sensitivity, optimal concentration of eerie ammonium sulfate, and optimal concentration of bromate and bromide ions, as well as the duration of bromate-bromide interaction with the sample. Resolution of the various factors studied resulted in the reported method for the determination of serum T4, together with an approach to the quantitation of iodine contamination based on the ratio of the second eluate to the sum of the first and second eluates. The method reported has a reproducibility of ± 0.16 to ± 0.32 μg. per 100 ml. (1 SD). A short survey of the correlation between levels of serum T4 and disease states is also presented.

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