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Measurement of 129I in fruit
Project Code: R01011
Westlakes Scientific Consulting
Attempts were made to measure the 129I-content of samples containing iodide solution and AgI powder using AMS. Sample preparation was conducted at Central Science Laboratories (CSL) and 129I analysis was conducted at Xceleron Ltd using Accelerator Mass Spectrometry. Attempts at analysis however, were unsuccessful. The 129I/127I ratio in the standards provided, ranged from 10-6 to 10-12. Difficulties were encountered in detecting the more abundantly present stable 127I. Hence the prospect of detecting the much lower levels of 129I could not be considered until problems in detecting 127I could be resolved. Such problems have not been overcome.
The information produced by CSL indicated that there was approximately 1.5 μg of 127I in 100 mg of carrier material such as NaCl. The injector magnet was set up to examine 127I from the cathode containing AgI powder and then, without any adjustment, the 127I output from a range of cathodes was checked. None of the cathodes with CSL-produced material gave a beam current of more than 45 nA (typical beam current should be of the order of 1 μA). Therefore, samples prepared using the method of acid-base digestion did not contain sufficient 127I to be analytically useful.
The method used in isolating iodine in the standard solution was UKAS accredited. However, the first step in the analytical process, of extracting iodine efficiently from the
standard/sample, could not be performed satisfactorily for AMS analysis, despite three attempts being made. Therefore the chemistry of iodine extraction from standards/samples
needs to be better understood.
From the experience gained in producing this report, it is recommended that the two-phase approach, as described in Section 2, be adopted for any future work on the analysis of 129I in fruit using AMS.
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