Determination of Uranium Isotopic Ratio by ICP-OES Using Optimal Sensitivity Position Analysis

Abstract

Isotopic composition analysis of natural and depleted uranium by inductively coupled plasma optical emission spectrometry (ICP-OES) requires the use of a high-resolution instrument due to the very slight isotopic shifts between the atomic emission spectra of the 238U and 235U isotopes. In this work, we show that conventional ICP-OES (without high-resolution optics) can be used for highly accurate uranium isotopic analysis, on par with the results obtained by ICP-MS. Such accurate measurements are achieved by applying a preparatory mathematical procedure termed the optimal sensitivity position (OSP) procedure. In the OSP procedure, a theoretical spectrum for 238U is constructed and subtracted from the measured spectra of calibration solutions encompassing various isotopic ratios. The resultant spectra are used to locate the optimal measurement positions for both major uranium isotopes (238U and 235U) and the background measurement position. Herein, the optimal measurement positions are revealed to be located not at each isotope’s peak maximum but at 424.427, 424.409, and 424.390 nm for 238U, 235U, and the background position, respectively. These locations remained stationary during the period of this work, implying that the use of a routine mathematical procedure is not required before every analysis. The OSP procedure offers a direct and highly accurate approach for determining the isotopic ratio of uranium in a relatively cheap and simple fashion. Furthermore, this work also demonstrates the possibility of greatly enhancing ICP-OES capabilities using mathematical analysis of spectra.

Rapid and Precise Uranium Isotopic Screening in Natural Water Using Bis(2-ethylhexyl)phosphoric Acid-Modified Membranes

“…It can be seen in Figure 6 that the external precisions between the replicate analysis of SRM-U010, obtained by monitoring 234 U/ 238 U and 234 U 16 O/ 238 U 16 O ion couples, are comparable. However, owing to the inherent advantages of using the Faraday transducer, such as (i) detector response is independent of energy, mass, and the chemical nature of ions, (ii) accurate output along with consistent sensitivity, and (iii) long-term gain stability, and so forth, most of the laboratories rely on ion collection by Faraday transducers.…”

“…Figure 5 also shows that there is a continuous decrease in the U + ion intensity obtained from the UO 2 CO 3 solution with an increasing analysis time, that is, at higher scan numbers. However, substantially high ion currents were obtained for 238 U 16 O + ions from UO 2 (NO 3 ) 2 −preloaded DEHPA-Dod@ PP membrane samples during the entire course of TIMS analysis. In addition to that, very stable ion currents of both U + and UO + ions were also observed for the UO 2 (NO 3 ) 2 − preloaded DEHPA-Dod@PP membrane, even when the VF current was maintained at a value as high as ∼3 A.…”

“…As mentioned earlier in Section 2, two sets of analyses were carried out independently, and the results are summarized in Table 1 and Figure 6. In the first set of analyses, the minor abundant isotope metal ion 234 U + and corresponding oxide ion 234 U 16 O + , that is, 234 U, were collected on a SEM system.…”

“…Most of the natural water samples contain detectable amounts of uranium: the average concentration in seawater is around 3 ppb, whereas groundwater may contain varying concentrations of uranium, ranging from less than 0.1 ppt to several ppm. , Because of the associated toxicity, uranium assay in natural water samples is of prime importance, and highly sensitive methods are required for monitoring trace or ultra-trace levels of uranium in water samples which are collected for prospective purposes. Although various instrumental techniques including spectrophotometry, fluorimetry, radiometry, atomic absorption/emission spectrometry, and XRF analyses are available for the determination of uranium, − mass spectrometric techniques, especially thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICP-MS), and accelerator mass spectrometry (AMS) are known to provide the most accurate and precise data for uranium measurement. − …”

A novel spectrofluorimetric method based on a reaction with an azoisoxazoles–benzenesulfonamide derivative for determination of uranium (VI) ions in water samples

“…As a result, it is critical to create simple, rapid, and reliable procedures for assessing water sources regarding radioactive pollutants. U(VI) content in different water samples has been determined using various techniques such as inductively coupled plasma–optical emission spectrometry (ICP–OES), [ 6 ] inductively coupled plasma–mass spectrometry (ICP‐MS), [ 7 ] high‐performance ion chromatography, [ 8 ] electrochemical analysis, [ 9 ] X‐ray fluorescence, [ 10 ] atomic emission spectrometry, [ 11 ] etc. However, these approaches have drawbacks such as the requirement for complicated technology, expensive instruments, and lengthy measuring processes, resulting in a decrease in their wide usage.…”