<p>A new method was developed to extract <sup>129</sup>I from urine
samples and then measure it by AMS. The samples were pre-treated in an
autoclave with hydrogen peroxide to remove unwanted compounds from the urine
samples and were acidified with nitric acid, followed by precipitation of
iodine as silver iodide (AgI) for measurement by AMS. This new procedure is
substantially faster than previous methods for the extraction of iodine from
urine and results in less chemical waste. The efficiency and reproducibility of
this method were evaluated by using <sup>125</sup>I as a yield tracer,
eventually giving a recovery above 99%. To achieve this, several iterations of
the method were required. The method was then successfully applied to measure <sup>129</sup>I/<sup>127</sup>I
isotopic ratios and <sup>129</sup>I concentrations in 25 human urine samples.
The AMS results for <sup>129</sup>I in urine ranged 3.3 x 10<sup>6</sup> atoms/L
to 884 x 10<sup>6</sup> atoms/L and the isotope ratio (<sup>129</sup>I/<sup>127</sup>I)
in human urine ranged from 7.38 x 10<sup>-12 </sup>to 3.97 x 10<sup>-10 </sup>with
a median of 1.29 x 10<sup>-10</sup>. This new method will be useful for
investigations into the sources of iodine in the human diet and their relative
importance for iodine sufficiency. </p>
<p> </p>