A Rapid Micro Method for Determining Diodrast and Inorganic Iodide Iodine in Blood and Urine.∗

The present paper describes a rapid micro method for the determination of diodrast or inorganic iodide iodine in whole blood, blood cells, plasma or urine. Hundreds of determinations of diodrast and inorganic iodide added to water, to urine and to filtrates have shown substantially a 100% recovery. With the method in its present form not all of the iodine is recovered from some other iodine compounds investigated, skiodan, iodeikon and isoiodeikon. The method has not been applied to normal blood or urine. The diodrast and skiodan used in this work were kindly furnished by the Winthrop Chemical Company; the iodeiokon and isoiodeikon by the Mallinckrodt Chemical Company. Principles of Method. The iodine-containing sample is digested in an acid solution of potassium permanganate, the iodine thereby being oxidized to iodate and the organic matter destroyed. The excess permanganate is reduced by addition of nitrite and the excess nitrite then destroyed by urea. The iodate is then titrated against a standard 0.0004715 N thiosulphate solution in the presence of an excess of potassium iodide. Procedures. With urine the determination is carried out on a diluted sample. With plasma it may be done either on 0.1 cc (or less, depending on iodine content) of plasma or on a sample of plasma filtrate. Because of their higher organic matter content it has not been found practicable to digest unprecipitated whole blood or cells; these determinations must be done on filtrates, where most of the organic matter has been removed. While determinations can be carried out on unprecipitated plasma, we usually use plasma filtrates, particularly at low iodine levels, since with these an amount equivalent to a larger amount of plasma can be used. With urine no precipitation is ever required.