Studies of the butanol-extractable iodine technique by the ceric oxidation method

Abstract

Investigations of the major procedural steps in a micro-BEI technique by the ceric oxidation method have been conducted. These studies have shown ( a) essentially complete thyroxine recovery from serum is accomplished by two 8–10 vol butanol extractions, ( b) two equal-volume Blau's reagent washes accomplish essentially complete iodide and tyrosine removal from the butanol extract, ( c) oxidative splitting of 3,5- and 3′,5′-thyroxine iodide by ceric ion under the present conditions is rapid and complete, ( d) chloride ion accentuates the catalytic effect of iodide in the decolorization (reduction) of ceric ion by arsenite without itself exerting a catalytic effect, and (e) coefficient of variation of the method over the range of 5 to 15 μg% BEI is about 5 to 8%. The present method, although subject to inhibition by serum and reagents, gives consistent results and offers precision equivalent to PBI techniques with the advantages of simplicity, specificity, and speed. The entire procedure requires only six to seven hours.