Abstract
Employing a commercial high-resolution inductively coupled plasma optical emission spectrometry (HR-ICP-OES) instrument, an innovative analytical procedure for the accurate determination of the production age of various Pu materials (Pu powder, cardiac pacemaker battery, (242)Cm heat source, etc.) was developed and validated. This undertaking was based on the fact that the α decay of (238)Pu present in the investigated samples produced (234)U and both mother and daughter could be identified unequivocally using HR-ICP-OES. Benefiting from the high spectral resolution of the instrument (<5 pm) and the isotope shift of the emission lines of both nuclides, (234)U and (238)Pu were selectively and directly determined in the dissolved samples, i.e., without a chemical separation of the two analytes from each other. Exact emission wavelengths as well as emission spectra of (234)U centered around λ = 411.590 nm and λ = 424.408 nm are reported here for the first time. Emission spectra of the isotopic standard reference material IRMM-199, comprising about one-third each of (233)U, (235)U, and (238)U, confirmed the presence of (234)U in the investigated samples. For the assessment of the (234)U/(238)Pu amount ratio, the emission signals of (234)U and (238)Pu were quantified at λ = 424.408 nm and λ = 402.148 nm, respectively. The age of the investigated samples (range: 26.7-44.4 years) was subsequently calculated using the (234)U/(238)Pu chronometer. HR-ICP-OES results were crossed-validated through sector field inductively coupled plasma mass spectrometry (SF-ICPMS) analysis of the (234)U/(238)Pu amount ratio of all samples applying isotope dilution combined with chromatographic separation of U and Pu. Available information on the assumed ages of the analyzed samples was consistent with the ages obtained via the HR-ICP-OES approach. Being based on a different physical detection principle, HR-ICP-OES provides an alternative strategy to the well-established mass spectrometric approach and thus effectively adds to the quality assurance of (234)U/(238)Pu age dates.
Highlights
Employing a commercial high-resolution inductively coupled plasma optical emission spectrometry (HRICP-OES) instrument, an innovative analytical procedure for the accurate determination of the production age of various Pu materials (Pu powder, cardiac pacemaker battery, 242Cm heat source, etc.) was developed and validated
Without such a chemical separation, 238Pu and 238U, for example, cannot be distinguished at mass 238 from each other with the abovementioned mass spectrometers rendering the reliable quantification of the 234U/238Pu amount ratio impossible
The superior optical resolution of HR-ICP-OES instruments, in turn, allows it to reveal the small difference in emission wavelengths evident for different U and Pu isotopes that is known as isotope shift.[1,8,9,11]
Summary
Employing a commercial high-resolution inductively coupled plasma optical emission spectrometry (HRICP-OES) instrument, an innovative analytical procedure for the accurate determination of the production age of various Pu materials (Pu powder, cardiac pacemaker battery, 242Cm heat source, etc.) was developed and validated. Pu and U isotopes are commonly quantified using isotope dilution method and applying mass spectrometric techniques such as inductively coupled plasma mass spectrometry (ICPMS), multicollector (MC)-ICPMS, and thermal ionization mass spectrometry (TIMS), and via α- and γ-spectrometry.[14−19] More recently, accelerator mass spectrometry (AMS) is applied to Pu and U isotopic analysis of environmental samples.[19−24] The aforementioned analytical approaches normally require a chemical separation of the U from Pu present in the actual sample to reduce the detrimental impact of spectral interferences that would otherwise hamper the reliable determination of specific Pu isotopes Without such a chemical separation, 238Pu and 238U, for example, cannot be distinguished at mass 238 from each other with the abovementioned mass spectrometers rendering the reliable quantification of the 234U/238Pu amount ratio impossible
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