Vol.:(0123456789) 1 3 Journal of Radioanalytical and Nuclear Chemistry (2020) 326:1879–1885 https://doi.org/10.1007/s10967-020-07381-5 Determination of aluminum in bovine liver SRM 1577c by Instrumental Cold Neutron Activation Analysis Rolf Zeisler 1  · Danyal Turkoglu 2  · Nick Sharp 1  · Heather Chen‑Mayer 1 Received: 30 June 2020 / Accepted: 5 September 2020 / Published online: 29 October 2020 © This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2020 Abstract Instrumental neutron activation analysis may need to correct for matrix interferences caused by fast neutron induced threshold reactions. The very low Al mass fraction in bovine liver Standard Reference Material (SRM) has eluded certification due to such complications. Cold neutron beam irradiation absent fast neutrons provides a possible alternative, which has been applied for the first time to determine Al in bovine liver SRM 1577c. The Al mass fraction was determined to be (0.80 ± 0.15) mg/kg using the traditional single peak-fitting method, and (0.78 ± 0.23) mg/kg using a new physics model-based spectral fitting method. Keywords Activation analysis · Cold neutron · Gamma ray background · Low Al concentration measurement · VRF fitting Introduction Although aluminum has no known biological function, it is a well-established neurotoxin that has controversially been implicated as a factor in neurodegeneration diseases such as Alzheimer’s [1]. Therefore, its determination is commonly considered in NIST biological standard reference materials (SRMs) that serve diagnostic, nutritional, and toxicological measurements in medical, veterinary, and environmental sciences. Al is assayed in instrumental neutron activation analysis (INAA) via detection of 1.7789 MeV gamma rays that are emitted following the 28 Al β − decay with a 2.24 min half-life (T 1/2 ). Quantification of Al by INAA, although sen- sitive to Al at mg/kg mass fractions, is susceptible to errone- ous results due to interferences in samples that contain Si and P, which produce other pathways to 28 Al (Fig. 1). For example, assuming a 1.18% mass fraction of P in the 1577c material, INAA in one of our irradiation facilities would produce 0.14 mg/kg excess Al during irradiation. This value would not be able to be corrected without knowing the exact amount of P in the sample (not detectable by INAA) and would cause an obvious bias on our results of 0.80 mg/kg (effectively a + 18% bias). The Al mass fraction eluded certification in the most recent bovine liver tissue SRM 1577c [2] due to the lack of agreement between independent measurements as required. For Al, one of the independent measurements is normally INAA in order to provide a value assignment. A “pre-irra- diation separation NAA” (PNAA) method [3] with modified digestion procedure and smaller sample sizes was neces- sary to reduce P in the sample for the determination of Al. However, the corrections for blank contributions from the pre-irradiation procedure add uncertainty to the result. The characterization of Al and V in SRM 1577c could not pro- ceed without PNAA [3]. Therefore, at present, direct INAA for Al certification is not feasible, mainly due to the inability to quantitatively control the pre-separation INAA necessi- tated by the presence of interfering reactions created by in- reactor irradiation. Irradiating bovine liver samples with cold neutron beams, termed Instrumental Cold Neutron Activation Analysis (ICNAA), avoids triggering the reactions that cause these interferences, and therefore is a good can- didate method to solve the problem. However, various Rolf Zeisler—deceased. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10967-020-07381-5) contains supplementary material, which is available to authorized users. * Heather Chen-Mayer chen-mayer@nist.gov 1 Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, USA 2 Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA