[Urinary iodide determination by X-ray fluorescence].

Urinary iodide measurement has been carried out by X-ray-fluorescence, either directly on urinary solution, or after matrix concentration. Proportionality between emitted XK alpha rays of iodine and iodide mass in standards has been observed on a large scale, ranging up to 400 micrograms. With an exciting-1.11 GBq (241(95) Am)-radioactive source, 0.44 microgram are detected for solid matrix, and 0.9 microgram/ml for iodide in solution for 10 mn measuring time. So direct measurement on solution can be applied only to high excreted iodide. For normal range iodide determination is performed after anionic resin concentration (on 100 ml or 200 ml). For tracing, Na I131 is employed. The binding ratio is strongly depending on flow, resin weight, and associate urinary anionic components. On 20 healthy subjects, normal range value is 53 +/- 22 micrograms/l (m +/- s.d.). Comparative study with an electrochemical method showed fluorescence iodide values are lower than the former. The proposed method is very simple, one or two steps (function of iodide content). As no interfered Rx has been observed in the Rx iodide region, the authors can ascertain that accurate values are observed by X-ray fluorescence. In case of high iodide content, this methods allows to distinguish urinary iodide versus total urinary iodine, when performing solution and matrix concentration studies on the urinary batch.