Clinical Chemistry, Vol 8, 17-34, Copyright © 1962 by the American Association for Clinical Chemistry

X-Ray Spectroscopy in the Clinical Laboratory

VI. Acid-Labile Protein-Bound Iodine

¹ Department of Biochemistry, Roosevelt Hospital, New York 19, N. Y. and Brooklyn College, Brooklyn, N. Y.

A procedure is described for the determination of protein-bound iodine of human serum with the X-ray spectrometer. The protein-bound iodine is extracted from serum at acid pH with alcohol-ether (3:1) solution. Evaporation of this extract results in the loss of the inorganic iodine. The residue is extracted with ammoniacal methanol, evaporated on filter paper, and exposed to the X-ray field. The L radiation is evaluated using the flow proportional counter. An instrument is described for evaporating the ammoniacal methanol in a confined area on the paper. The residue from the alcohol-ether extract may also be digested, with the liberated iodine distilled onto a small circle of filter paper (in a simple apparatus described) and the filter paper exposed to the X-ray field. The procedure requires 2 ml. of serum.

Levels obtained by this method are somewhat lower than those obtained by an ashing procedure followed by the ceric-arsenite reaction. The X-ray method is more precise than the conventional procedures. In preliminary studies, the mean normal value found by this method was 4.7 µg./100 ml. of serum, with a range of ± 0.6 (2 ).