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Concept: Accelerator mass spectrometry

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Centennial-scale mineral dust peaks in last glacial Greenland ice cores match the timing of lowest Greenland temperatures, yet little is known of equivalent changes in dust-emitting regions, limiting our understanding of dust-climate interaction. Here, we present the most detailed and precise age model for European loess dust deposits to date, based on 125 accelerator mass spectrometry 14C ages from Dunaszekcső, Hungary. The record shows that variations in glacial dust deposition variability on centennial-millennial timescales in east central Europe and Greenland were synchronous within uncertainty. We suggest that precipitation and atmospheric circulation changes were likely the major influences on European glacial dust activity and propose that European dust emissions were modulated by dominant phases of the North Atlantic Oscillation, which had a major influence on vegetation and local climate of European dust source regions.

Concepts: Greenland, Mass spectrometry, Accelerator mass spectrometry, Ice core, Ice, Atlantic Ocean, Earth, Europe

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Dalcetrapib, a thioester prodrug, undergoes rapid and complete conversion in vivo to its phenothiol metabolite M1 which exerts the targeted pharmacological response in human. In clinical studies, M1 has been quantified together with its dimer and mixed disulfide species that represent the ‘dalcetrapib active form’ in plasma. In this article, we describe the determination of the free phenothiol M1 by derivatisation with methylacrylate as a percentage of ‘dalcetrapib active form’. Pharmacokinetic profiles of M1 after oral administration of dalcetrapib to humans could be established, underscoring the validity to use a composite measure of ‘dalcetrapib active form’ as a surrogate marker for pharmacodynamic evaluations. ‘Dalcetrapib active form’ and M1 made up 8.9% and 3.6% of total drug-related material, respectively. In addition, complete metabolite profiling of 14C-labeled dalcetrapib was conducted after two-dimensional HPLC using fast fractionation into 384-well plates and ultrasensitive determination of the 14C-content by accelerator mass spectrometry. M1 underwent further biotransformation to its S-methyl metabolite M3, which was further oxidized to its sulfoxide and sulfone. Another metabolic pathway was the formation of the S-glucuronide. All of these species underwent further oxidation in the ethylbutyl cyclohexyl moiety leading to a multitude of hydroxyl and keto metabolites undergoing further conjugation to O-glucuronides. More than 80 metabolites were identified, demonstrating extensive metabolism. However, it was unambiguously demonstrated that none of these metabolites were major according to the MIST guideline (exceeding 10% of drug related material in circulation). The combination of accelerator mass spectrometry with HPLC together with high resolution mass spectrometry allowed for structural characterization of the most relevant human metabolites.

Concepts: Spectroscopy, Accelerator mass spectrometry, Functional group, Pharmacokinetics, Alcohol, Pharmacology, Mass spectrometry, Metabolism

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Benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH), is a known human carcinogen. In non-smoking adults greater than 95% of BaP exposure is through diet. The carcinogenicity of BaP is utilized by the U.S. EPA to assess relative potency of complex PAH mixtures. PAH relative potency factors (RPFs, BaP = 1) are determined from high dose animal data. We employed accelerator mass spectrometry (AMS) to determine pharmacokinetics of [14C]-BaP in humans following dosing with 46 ng (an order of magnitude lower than human dietary daily exposure and million-fold lower than animal cancer models). To assess the impact of co-administration of food with a complex PAH mixture, humans were dosed with 46 ng of [14C]-BaP with or without smoked salmon. Subjects were asked to avoid high BaP-containing diets and a 3-day dietary questionnaire given to assess dietary exposure prior to dosing and three days post-dosing with [14C]-BaP. Co-administration of smoked salmon, containing a complex mixture of PAHs with an RPF of 460 ng BaPeq, reduced and delayed absorption. Administration of canned commercial salmon, containing very low amounts of PAHs, showed the impacts on pharmacokinetics were not due to high amounts of PAHs but rather a food matrix effect.

Concepts: Accelerator mass spectrometry, Salmon, Diet, Carcinogen, Human, Mass spectrometry, Benzene, Polycyclic aromatic hydrocarbon

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In this work we present and evaluate a radiochemical procedure optimised for the analysis of 236U and 239,240Pu in seawater samples by Accelerator Mass Spectrometry (AMS). The method is based on Fe(OH)3 co-precipitation of actinides and uses TEVA® and UTEVA® extraction chromatography resins in a simplified way for the final U and Pu purification. In order to improve the performance of the method, the radiochemical yields are analysed in 1 to 10L seawater volumes using alpha spectrometry (AS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Robust 80% plutonium recoveries are obtained; however, it is found that Fe(III) concentration in the precipitation solution and sample volume are the two critical and correlated parameters influencing the initial uranium extraction through Fe(OH)3 co-precipitation. Therefore, we propose an expression that optimises the sample volume and Fe(III) amounts according to both the 236U and 239,240Pu concentrations in the samples and the performance parameters of the AMS facility. The method is validated for the current setup of the 1MV AMS system (CNA, Sevilla, Spain), where He gas is used as a stripper, by analysing a set of intercomparison seawater samples, together with the Laboratory of Ion Beam Physics (ETH, Zürich, Switzerland).

Concepts: Plutonium, Concentration, Chemistry, Accelerator mass spectrometry, Ion source, Spectroscopy, Analytical chemistry, Mass spectrometry

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A rapid method with enhanced 238U decontamination was developed for ultra-trace Pu analysis in small-volume urine bioassays. This method consists of acid digestion, co-precipitation, extraction chromatography and sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) measurement. Parameters that may influence the analytical performance were studied systematically. This method achieved a high 238U decontamination factor (3.8 × 106) and the 242Pu recovery was stable for 20 mL and 100 mL urine bioassays with an average value of 72.7 ± 5.5%. The limits of detection for 239Pu, 240Pu and 241Pu by the method were 0.016 fg mL-1, 0.016 fg mL-1 and 0.019 fg mL-1 for 20 mL urine samples and 0.003 fg mL-1, 0.002 fg mL-1 and 0.003 fg mL-1 for 100 mL urine samples, respectively. Considering the small volume of urine employed in this study, the absolute detection limits of the method were comparable or even better than those measured with thermal ionization mass spectrometry and accelerator mass spectrometry. All procedures for 20 mL and 100 mL urine bioassays were completed in 9.5 h and 11 h, respectively, and analysis of 10 samples could be finished within one day. With the considerably low detection limits of Pu isotopes and high sample throughput, this method would be a promising tool for the quick response to radiological emergencies and for rapid screening of unexpected occupational exposures of workers involved in the future FDNPP reactor decommissioning operations.

Concepts: Isotopes of plutonium, Urinalysis, Measurement, Analytical chemistry, Accelerator mass spectrometry, Spectroscopy, Plutonium, Mass spectrometry

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Although regulatory guidances require human metabolism information of drug candidates early in the development process, the human mass balance study (or hADME study), is performed relatively late. hADME studies typically involve the administration of a14C-radiolabelled drug where biological samples are measured by conventional scintillation counting analysis. Another approach is the administration of therapeutic doses containing a14C-microtracer followed by accelerator mass spectrometry (AMS) analysis, enabling hADME studies completion much earlier. Consequently, there is an opportunity to change the current drug development paradigm.

Concepts: Opportunity rover, Scintillation counter, The Current, Mass, Spectroscopy, Accelerator mass spectrometry, Metabolism, Mass spectrometry

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The assessment of the radiological impact of decommissioning activities at a Nuclear Power Plant requires a detailed mapping of the distribution of radionuclides both in the environment surrounding the NPP and in its structural material. The detection of long-lived actinide isotopes and possibly the identification of their origin is particularly interesting and valuable if ultrasensitive measurement of the relative abundance of U isotopes is performed via Accelerator Mass Spectrometry (AMS). In this paper we present an investigation carried out on the structural materials of the Garigliano NPP aiming to determine the abundance of 235,236,238U in the various compartments of the plant buildings under decommissioning. Since the expected values both for isotopic ratios and total U concentrations range over different orders of magnitude, we have developed a novel methodology for the measurement of 234,235U/238U isotopic ratios in low U concentration samples. This allowed a systematic investigation of the distribution of all U isotopes in concrete and metal matrices of the NPP. The behavior of 235,236U/238U isotopic ratios in the different compartments of the NPP is discussed. The correlation of these ratios with 60Co and 137Cs specific activities is also studied to show a different behavior for concrete and metal samples. These data represent a very valuable information to direct the decommissioning procedures under course.

Concepts: Isotopes, Abundance of the chemical elements, Accelerator mass spectrometry, Uranium, Nuclear physics, Nuclear power, Mass spectrometry, Isotope

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Measurements of the long-lived radionuclide 236U are an important endeavor, not only in nuclear safeguards work, but also in terms of using this emerging nuclide as a tracer in chemical oceanography, hydrology, and actinide sourcing. Depending on the properties of a sample and its neutron irradiation history, 236U/238U ratios from different sources vary significantly. Therefore, this ratio can be treated as an important fingerprint for radioactive source identification, and in particular, affords a definitive means of discriminating between naturally occurring U and specific types of anthropogenic U. The development of mass spectrometric techniques makes it possible to determine ultra-trace levels of 236U in environmental samples. In this paper, we review the current status of mass spectrometric approaches for determination of 236U in environmental samples. Various sample preparation methods are summarized and compared. The mass spectrometric techniques emphasized herein are thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICP-MS) and accelerator mass spectrometry (AMS). The strategies or principles used by each technique for the analysis of 236U are described. The performances of these techniques in terms of abundance sensitivity and detection limit are discussed in detail. To date, AMS exhibits the best capability for ultra-trace determinations of 236U. The levels and behaviors of 236U in various environmental media are summarized and discussed as well. Results suggest that 236U has an important, emerging role as a tracer for geochemical studies.

Concepts: Determination, Analytical chemistry, Radioactive decay, Identification, Isotope, Accelerator mass spectrometry, Spectroscopy, Mass spectrometry

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A new procedure using polyethersulfone (PES) microextraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was developed in this work for the simultaneous determination of 41 multiclass priority and emerging organic pollutants including herbicides, hormones, personal care products, and pharmaceuticals, among others, in seawater, wastewater treatment plant (WWTP) effluents, and estuary samples. The optimization of the analysis included two different chromatographic columns and different variables (polarity, fragmentor voltage, collision energy, and collision cell accelerator) of the mass spectrometer. In the case of PES extraction, ion strength of the water, pH, addition of EDTA, and the amount of the polymeric material were thoroughly investigated. The developed procedure was compared with a previously validated one based on a standard solid-phase extraction (SPE). In contrast to the SPE protocol, the PES method allowed a cost-efficient extraction of complex aqueous samples with lower matrix effect from 120 mL of water sample. Satisfactory and comparable apparent recovery values (80-119 and 70-131%) and method quantification limits (MQLs, 0.4-26 and 0.2-23 ng/L) were obtained for PES and SPE procedures, respectively, regardless of the matrix. Repeatability values lower than 27% were obtained. Finally, the developed methods were applied to the analysis of real samples from the Basque Country and irbesartan, valsartan, acesulfame, and sucralose were the analytes most often detected at the highest concentrations (51-1096 ng/L). Graphical abstract Forty-one multiclass pollutant determination in environmental waters by means of PES/SPE-LC-MS/MS.

Concepts: Accelerator mass spectrometry, Basque Country, Analytical chemistry, Liquid chromatography-mass spectrometry, Water, Mass spectrometry, Sewage treatment

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This two-part, phase I study evaluated the mass balance, excretion, pharmacokinetics (PK), and safety of ixazomib in patients with advanced solid tumors. In Part A of the study, patients received a single 4.1 mg oral solution dose of [(14)C]-ixazomib containing ~500 nCi total radioactivity (TRA), followed by non-radiolabeled ixazomib (4 mg capsule) on days 14 and 21 of the 35-day PK cycle. Patients were confined to the clinic for the first 168 h post dose and returned for 24 h overnight clinic visits on days 14, 21, 28, and 35. Blood, urine, and fecal samples were collected during Part A to assess the mass balance (by accelerator mass spectrometry), excretion, and PK of ixazomib. During Part B of the study, patients received non-radiolabeled ixazomib (4 mg capsules) on days 1, 8, and 15 of 28-day cycles. After oral administration, ixazomib was rapidly absorbed with a median plasma Tmax of 0.5 h and represented 70% of total drug-related material in plasma. The mean total recovery of administered TRA was 83.9%; 62.1% in urine and 21.8% in feces. Only 3.23% of the administered dose was recovered in urine as unchanged drug up to 168 h post dose, suggesting that most of the TRA in urine was attributable to metabolites. All patients experienced a treatment-emergent adverse event, which most commonly involved the gastrointestinal system. These findings suggest that ixazomib is extensively metabolized, with urine representing the predominant route of excretion of drug-related material.Trial ID: ClinicalTrials.gov # NCT01953783.

Concepts: Metabolism, Benign tumor, Arithmetic mean, Accelerator mass spectrometry, Digestion, Mass spectrometry