On-line preconcentration and determination of iron by flow injection analysis in nuclear fuels S. Chandramouleeswaran 1 • Jayshree Ramkumar 1 Received: 27 August 2018 Ó Akade ´miai Kiado ´, Budapest, Hungary 2018 Abstract Determination of trace level of iron in metallic uranium is of great importance. The developed procedure involves online pre-concentration and separation of iron and its determination using flow injection analysis system. The analyte forms complex with mandelic acid and retained in the micro column packed with cation exchanger and matrix goes to waste. The eluted iron was determined and the detection limit of the method is 5 ppb with a precision (RSD) at 100 ppb level of 6.2%. Keywords Flow injection analysis Á Iron Á Uranium matrix Á Chelating group Á On-line pre-concentration Introduction Analysis of uranium metal prior to its use as nuclear fuel is very important as it helps in acceptance of the particular sample for further use as fuel. It is a common practice to check for the specifications of uranium metal with respect to different trace level metallic impurities. There are large numbers of analytical techniques that are usually adopted for this purpose but the limitation associated with a par- ticular technique or procedure gives way for further development of newer analytical procedures. One of the most important metallic impurities in ura- nium is Iron (Fe). It is a non nuclear impurity and the maximum allowed limit in metallic nuclear fuel is 150 lg/ g. The main source of iron is from the MgF 2 slag (contains 1000–2000 lg/g of Fe) that is used as lining material in mild steel reactor during the production of metallic ura- nium via magneso-thermic reduction of UF 4 [1, 2]. Direct spectrochemical determination of metallic impurities is made impossible due to the complex spectra of the uranium matrix. Hence the need for an alternative technique arises. Most of the techniques deal with the separation of the uranium matrix by solvent extraction [3] using solvents like Tributyl phosphate (TBP) [4], di-(2-ethyl-hexyl) phosphate (D2EHP) and tri-(2-ethyl-hexyl)-phosphate (T2EHP) [5], di-(2-ethylhexyl)-phosphoric acid (DEHPA) and TBP [6]. The studies showed that TBP extraction have been carried out in highly acidic medium or in synergism with other reagents to ensure complete removal of uranium matrix in order to improve the sensitivity and detection limit of the methodology. It is to be noted that in most of the solvent extraction procedures, the uranium matrix is removed to the maximum possible level so as to not to show any interference during the analysis of the metallic impurity. In our recent study [7], we have used the well known extractant tributyl phosphate (TBP) to bring about selective separation of iron from uranium matrix and applied it to the uranium turning samples. The main highlight of this work [7] was that normally uranium matrix is removed by TBP extraction. However, the co- extraction of iron is a very common issue. Hence TBP was first used to extract both uranium and iron into the organic phase and by using suitable acid concentration, only iron could be stripped out into the aqueous phase thus resulting in the near complete removal of iron from uranium prior to the determination of iron. XRF was used for determination of very high concentrations of iron in presence of uranium [8] but this could not be applied to uranium samples con- taining lower levels of iron. Therefore it was of interest to try to develop an alternate technique which would be fast and simple. This could either be carried out without the separation of matrix. If this was not possible, then a methodology based on online & Jayshree Ramkumar jrk@barc.gov.in 1 Analytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India 123 Journal of Radioanalytical and Nuclear Chemistry https://doi.org/10.1007/s10967-018-6273-7