[Development of the certified reference material of iodine in lyophilized human urine]

Urine samples from normal level and low level iodine districts were filtered, homogenized, dispensed, lyophilized and radio-sterilized. Homogeneity test, stability inspection and certification were conducted using a spectrophotometric method. The physical and chemical stability of the CRM (Certified reference material) were assessed for one year. The certified values are based on analysis made by five independent laboratories using three different principle methods. The certified values +/- uncertainties are as follows: low level is (121 +/- 14) micrograms/L, normal level is (201 +/- 11) micrograms/L.