A procedure for the sequential determination of radionuclides in soil and sediment samples Hans Sahli 1 • Stefan Ro ¨llin 1 • Viktoria Putyrskaya 2 • Eckhard Klemt 2 • Be ´atrice Balsiger 1 • Mario Burger 1 • Jose ´ A. Corcho Alvarado 1 Received: 30 August 2017 Ó Akade ´miai Kiado ´, Budapest, Hungary 2017 Abstract We present a new radiochemical procedure for the sequential determination of Sr, Am, Pu, Th and U radionuclides. For the validation, seven IAEA certified reference materials were analyzed for 239 Pu, 240 Pu, 241 Pu, 238 U and 232 Th isotopes by ICP-MS, 243 Am by alpha spectrometry and 90 Sr by low level gas proportional counting. The sequential method was then used for deter- mining the radionuclide profiles in one sediment core collected in the River Rhine, near Augst, downstream of the Swiss nuclear power plants. Keywords 240 Pu/ 239 Pu Á River Rhine Á Sediments Á Switzerland Introduction Sequential methods enable the simultaneous determination of several radionuclides in the same sample and, therefore, a better understanding of correlation between radionuclides [1–9]. The correlation between radionuclides (or isotopic ratios) provide, in many cases, information such as the type or origin of the contamination (e.g. 241 Am/ 239,240 Pu, 238 Pu/ 239,240 Pu). Some of them may also provide quanti- tative information about the date of the contamination, like, for example, 241 Am/ 241 Pu [10]. Another important advan- tage of sequential methods is the reduction of time and cost of analysis by performing the sample preparation (e.g. drying, sieving, ashing, digestion, etc.) only once. Sequential determinations are particularly useful when several radionuclides must be determined in a limited amount of sample that is not sufficient for determining single radionuclide separately. This is for e.g. often the case for sediment core samples, which are normally diffi- cult and expensive to collect. Sequential determination is as well necessary in emergency situations, where infor- mation about several radionuclides is required on a short period of time [11, 12]. A common problem to deal with in sequential deter- minations, rarely discussed in the literature, is the potential contamination of the analyte of interest by impurities present in the tracer used for the radiochemical recovery determination. For example, the 243 Am standard tracer which is used for 241 Am determination commonly contain trace amounts of 239 Pu. 242 Pu tracer solutions, used for Pu isotopes determinations, contains as well trace quantities of 241 Am (from 241 Pu). In order to correctly determine 239 Pu and 241 Am in a sequential determination, the contributions from the tracer solutions have to be taken into account. Another unavoidable problem of using sequential methods is the lowering of the radiochemical recovery for some of the analytes. This is a result of the additional steps that are required in a sequential method compared to single determinations. We present in detail the radiochemical procedure used at Spiez Laboratory (Switzerland) for the sequential deter- mination of 90 Sr, 241 Am, Pu, Th and U radionuclides in soil and sediment samples. The procedure is based on the use of extraction chromatography separations in combination with co-precipitation methods. A flow chart of the sequential method is shown in Fig. 1. This paper presents the results of the validation of the sequential method by using certified & Jose ´ A. Corcho Alvarado jose.corcho@babs.admin.ch 1 Spiez Laboratory, Physics Division, Federal Office for Civil Protection, 3700 Spiez, Switzerland 2 Hochschule Ravensburg-Weingarten, University of Applied Sciences, 88250 Weingarten, Germany 123 J Radioanal Nucl Chem DOI 10.1007/s10967-017-5621-3