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A fully automated isotopic profile deconvoluted chromatogram (IPDC) algorithm (Fakouri Baygi et al. in Anal Chem 91:15509–15517, 2019) and user interactive HaloSeeker 1.0 (Léon et al. in Anal Chem 91:3500–3507, 2019) were compared to test the efficacy of these two computationally enhanced non-targeted screening (CENTS) tools in isolating unknown Br/Cl compounds using high-resolution mass spectrometry (HRMS) data. HaloSeeker depends on a user to monitor the performance of the peak picking algorithm and assign molecular formulas for each isotopic signature in an ergonomic interface. Alternatively, the IPDC algorithm automatically assigns and ranks candidate molecular formulas within a set of search criteria. Both CENTS tools were evaluated using fish and sediment data acquired at 22,000 (mHRMS) and > 100,000 (uHRMS) mass resolutions, respectively. The IPDC algorithm detected 85% of compounds detected by HaloSeeker as the first candidate compound in the sediment sample, with fewer false positives. In the sediment data, the IPDC algorithm detected several compounds such as clofoctol and chlorinated paraffins that were not reported using HaloSeeker 1.0. Upon further inspection, these compounds were isolated by the HaloSeeker program, but not reported by the user. HaloSeeker detected all significant and insignificant chemical ionization products (relative to IPDC), but additional false positives were isolated in the mHRMS polychlorinated biphenyl reference standard and trout sample. HaloSeeker detected 62% of the legacy contaminant features isolated by the IPDC algorithm in the fish data (mHRMS). The comparison of these two CENTS tools demonstrates that matrix complexity and mass resolution of the HRMS platform are the key factors when choosing automated and user interactive CENTS tools. [ABSTRACT FROM AUTHOR]

The article presents the isotopic profiling of natural uranium mined from northern Nigeria for nuclear forensic application.

Four mined samples of natural uranium from northern Nigeria were studied through inductively coupled plasma mass spectrometry, at the Environmental Analytical Chemistry Laboratory, University of the Witwatersrand, Johannesburg. The samples were characterised for lead, thorium and uranium isotopic concentrations, isotopic ratios and age. The objective was to obtain nuclear forensic fingerprints as baseline data to add to the Nigerian National Nuclear Forensic Library. Results showed significant variation in the isotopic concentrations of lead, thorium and uranium across the mines. Isotopic ratios of 238U/235U, 235U/238U and 234U/238U across the sample of 137.881±0.007, 7.253×10-03±2.05×10-04 and 5.540×10-05±4.08×10-07 were found to be consistent with the natural values. The age of natural uranium is comparable to the age of earth. Uranium, lead, and thorium isotopic concentrations and ratios, as well as the age of the samples characterised, provide an isotopic profile that can be used for nuclear forensic application. Significance: • Given the abundant deposits of natural uranium in Africa and the consequent potential for nuclear insecurity, determining the isotopic profiles and signatures of natural uranium is important for application in nuclear forensics. • Isotopic concentrations of 232Th, 238U, 235U and 234U from the respective sampling sites differed significantly, thereby providing characteristic isotopic profiles.