Comparison of alkali fusion and acid digestion methods for radiochemical separation of Uranium from dietary samples

Several methods exist for separation and measurement of uranium in dietary samples such as neutron activation analysis (NAA), alpha spectrometric determination, inductively coupled plasma mass spectrometry (ICP-MS) and fluorimetry. For qualitative determination of activity, NAA and alpha spectrometry are said to be superior to evaluate the isotopes of uranium (²³⁸U, ²³⁴U and ²³⁵U). In case of alpha spectrometry, the samples have to undergo radiochemical analysis for separation from other elements for uranium detection. In our studies, uranium was determined in food matrices by acid digestion (AD) and alkali fusion (AF) methods. The recovery yield of uranium in food matrices was compared in order to get consistent yield. The average activity levels of ²³⁸U and ²³⁴U in food samples were calculated based on recovery yield of ²³²U in the samples. The average recovery of ²³²U in AD method was 22 ± 8% and in AF method, it was 14.9 ± 1.3%. The spread is more in AD method than the AF method from their mean. The lowest recovery of ²³²U was found in AF method. This is due to the interference of other elements in the sample during electroplating. Experimental results showed that the uranium separation by AD method has better recovery than the AF method. The consistency in recovery of ²³²U was better for AF method, which was lower than the AD method. However, overall for both the methods, the recovery can be termed as poor and need rigorous follow up studies for consistently higher recoveries (>50%) in these type of biological samples. There are reports indicating satisfactory recoveries of around 80% with ²³²U as tracer in the food matrices