scholarly journals Uranium, thorium, and potassium analyses using pXRF spectrometry

2021 ◽  
Author(s):  
R D Knight ◽  
B A Kjarsgaard ◽  
E G Potter ◽  
A Plourde
Keyword(s):  
Reference Materials ◽  
Certified Reference Materials ◽  
Standard Reference Materials ◽  
Regression Equations ◽  
Exponential Relationship ◽  
Icp Ms ◽  
Total Digestion ◽  
Correction Curve ◽  
High Concentrations ◽  
Digestion Methods

The application of portable XRF spectrometry (pXRF) for determining concentrations of uranium (U), thorium (Th) and potassium (K) was evaluated using a combination of 12 Certified Reference Materials, 17 Standard Reference Materials, and 25 rock samples collected from areas of known U occurrences or mineralization. Samples were analysed by pXRF in Soil, Mining Cu/Zn and Mining Ta/Hf modes. Resulting pXRF data were compared to published recommended values, obtained by total or near total digestion methods with ICP-MS and ICP-OES analysis. Results for pXRF show a linear relationship, for thorium, potassium, and uranium (<5000 ppm U) as compared to the recommended concentrations. However, above 5000 ppm U, pXRF results show an exponential relationship with under reporting of pXRF concentrations compared to recommended values. Accuracy of the data can be improved by post-analysis correction using linear regression equations for potassium and thorium, and samples with <5000 ppm uranium; an exponential correction curve is required at >5000 ppm U. In addition, pXRF analyses of samples with high concentrations of uranium (e.g. >1 wt.% U) significantly over-estimated potassium contents as compared to the published values, indicating interference between the two elements not calibrated by the manufacturer software.

scholarly journals 230Th-234U model ages of some uranium standard reference materials

2011 ◽  
Vol 1 (1) ◽  
pp. 31-35 ◽  
Author(s):  
R. W. Williams ◽  
A. M. Gaffney
Keyword(s):  
Reference Materials ◽  
Closed System ◽  
Half Life ◽  
Certified Reference Materials ◽  
Isotope Dilution Mass Spectrometry ◽  
Standard Reference Materials ◽  
National Bureau ◽  
System Behavior ◽  
Icp Ms ◽  
Solid Form

Abstract The “age” of a sample of uranium is an important aspect of a nuclear forensic investigation and of the attribution of the material to a source. The 230Th- 234U chronometer can be used to determine the production date of even very recently-produced material ( 234U half life = 245250 ± 490 years; 230Th half life = 75690 ± 230 years [1]), provided that the 230Th/234U at the time of formation is known, and that there has been no Th-U fractionation in the sample since production. For most samples of uranium, ages determined with this chronometer are “model ages”, because they are based on the assumptions of a) some initial amount of 230Th in the sample, and b) closed-system behavior of the sample since production. The uranium standard reference materials originally prepared and distributed by the former US National Bureau of Standards and now distributed by New Brunswick Laboratory as certified reference materials (NBS SRM = NBL CRM) are good candidates for materials where these assumptions may be tested. The U isotopic standards have known purification and production dates and closed-system behavior in the solid form (U3O8) may be reliably assumed. In addition, these materials are widely available and can serve as informal round-robin inter-laboratory comparison samples. We determined 230Th-234U model ages for seven of these isotopic standards by isotope dilution mass spectrometry using a multi-collector ICP-MS. The standards dated for this study are U005-A, U010, U030-A, U100, U850, U900 and U970. Model ages obtained range from ∼ 30 to ∼ 52 years ago (reference date: 5-May-2009). The model age of U100 is the same as the purification date, within uncertainty. The other six standards analyzed all give model ages older than the purification dates of record. The magnitude of the discrepancy between model age and purification date does not correlate with the model age or the amount of 232Th in the samples. This indicates that excess 230Th in these six standards results from incomplete purification during production.

A Method for the Routine Determination of Methylmercury in Marine Tissue by GC Isotope Dilution-ICP-MS

2012 ◽  
Vol 95 (4) ◽  
pp. 1189-1194 ◽  
Author(s):  
Stig Valdersnes ◽  
Amund Maage ◽  
Daniel Fliegel ◽  
Kåre Julshamn
Keyword(s):  
Reference Material ◽  
Reference Materials ◽  
Isotope Dilution ◽  
Isotope Dilution Mass Spectrometry ◽  
Standard Reference Materials ◽  
Statistical Measures ◽  
Icp Ms ◽  
Wide Range ◽  
Z Scores

Abstract Currently, there is no legal limit for methyl mercury (MeHg) in food; thus, no standardized method for the determination of MeHg in seafood exists within the European jurisdiction. In anticipation of a future legislative limit an inductively coupled plasma isotope dilution mass spectrometry (GC-ICP-ID-MS) method was developed in collaboration with the European Standardization Organization (CEN). The method comprises spiking the tissue sample with Me201Hg, followed by decomposition with tetramethylammonium hydroxide, pH adjustment and derivatization with sodium tetraethylborate, and finally organic extraction of the derivatized MeHg in a hexane phase. Subsequently, the sample is analyzed via GC-ICP-MS and the result calculated using the ID equation. The working range of the method was 0.0005–1.321 mg/kg MeHg in marine tissue, with an internal reproducibility (RSD) of 12–1%. The method was validated based on statistical measures, such as the z-scores, using the commercially available reference materials from National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1566b, NIST SRM 2977 and National Research Council of Canada (NRCC) TORT 2, NRCC, DORM 3, NRCC DOLT 4, and European Reference Material (ERM) CE 464. Z-scores for all standard reference materials, except for NIST SRM 1566b, were better than |1.5|. The wide range of marine tissues used during the validation ensures that the method will be applicable for measuring of MeHg in seafood matrixes of all kinds.

How to use and how not to use certified reference materials in industrial chemical metrology laboratories

2020 ◽  
Vol 35 (2) ◽  
pp. 104-111
Author(s):  
John R. Sieber
Keyword(s):  
Analytical Chemistry ◽  
Reference Materials ◽  
Certified Reference Materials ◽  
International System ◽  
Test Methods ◽  
Standard Reference Materials ◽  
Chemical Metrology ◽  
Laboratory Staff ◽  
Material Development ◽  
System Of Units

As a producer of certified reference materials (CRMs), NIST faces high demand for Standard Reference Materials (SRMs). The demand is exacerbated by widespread misuse of CRMs. When should one use CRMs? When should one not use CRMs? Must labs always use NIST SRMs? How can labs demonstrate analytical capabilities for their accreditation scopes? Why so many questions? Standards developers, laboratory accreditors, and laboratory staff must be able to understand these topics with respect to quality systems in compliance with ISO/IEC 17025. They must calibrate and validate test methods and document traceability to the International System of Units (SI). Many people working in laboratory accreditation and under the umbrella of a quality system do not fully understand what these things are, let alone the language of chemical metrology. On average, they have little training in analytical chemistry, elemental analysis, and reference material development. It is hoped this paper will impress upon the reader the need for understanding how CRMs can be best used in the laboratory. This paper provides a brief background on the above problems and then looks at some of the support and reference information provided by NIST to metals and mining industries labs, commercial CRM producers, and accrediting bodies. The concepts and guidance apply broadly to chemical metrology and fundamental analytical chemistry. The paper includes examples (some from X-ray fluorescence spectrometry) to illustrate concepts.

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