Evaluation of resonance ionization mass spectrometry for the determination of ¹³⁵Cs/¹³⁷Cs isotope ratios in low-level samples

Abstract

Resonance ionization / Trace analysis / 135 Cs/ 137 Cs isotope ratios / Mass spectrometry Summary. The ability of Resonance Ionization Mass Spectrometry (RIMS) to reliably determine the ratio of 135 Cs/ 137 Cs in the presence of large backgrounds has been evaluated. Singleresonance excitation of Cs 6s 2 S 1/2 (F = 4) → 6 p 2 P 3/2 (F = 5) with an extended cavity diode laser was followed by photoionization with the 488 nm line of an argon ion laser. While the principal objective was to avoid isobaric interferences, an optical selectivity of 3 orders of magnitude against stable 133 Cs was attained for both 135 Cs and 137 Cs. The overall RIMS efficiency was found to be ∼ 2 × 10 −6 with a combined (laser and mass spectrometer) selectivity of ∼ 10 10 for both 135 Cs and 137 Cs against 133 Cs. The performance with respect to efficiency, selectivity, and isobar suppression has been compared to conventional thermal ionization mass spectrometry (TIMS). Measurements to determine the chronological age of a burn-up sample have been performed using both methods.

Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples

“…Due to the interference of 99 Ru and 98 MoH in the ICP-MS determination of 99 Tc, the high concentrations of Mo and Ru in environmental samples have to be removed. For this purpose, two TEVA column was used, and a decontamination factor of 10 4 ~10 5 for Ru and Mo was obtained.…”

“…RIMS as a highly selective and sensitive mass spectrometric technique for ultratrace and isotope analysis has been used for the analysis of many radionuclides such as 41 Ca, 90 Sr, 99 Tc, 135 Cs, 210 Pb, 236 U, 238 Pu, 239 Pu, 240 Pu, 242 Pu, and 244 Pu in environmental, biological and waste samples [33,34,[94][95][96][97][98][99][100][101][102][103][104][105]. In RIMS the solid or liquid samples are vaporized and atomized by an atomic beam source (e.g.…”

“…The possible contributors to the 99 peak background are listed in Table 8. Isobaric interferences from the stable isotope 99 Ru, abundance sensitivity or tailing of 98 Mo and 100 Mo, and the 98 MoH + molecular ion are the main interferences in the analysis of environmental samples using ICP-MS [46]. Due to high concentration of Ru (0.7 ng/l in seawater) compared to 99 Tc in environmental samples (<8-5000 × 10 -6 ng/l) and a high isotopic abundance of 99 Ru (12.7%), a high decontamination factor (10 6 -10 7 ) for Ru is required.…”

“…The contribution from 98 Mo to mass 99 was mainly due to abundance sensitivity and in a less extent due to formation of the 98 The chemical separation techniques used in radiometric methods can also be used for the mass spectrometric determination of 99 Tc. The main difference is that the separation methods used for radiometric determination focuses on the removal of radionuclides, the stable elements in the reagents and apparatus are not of importance.…”

“…The main difference is that the separation methods used for radiometric determination focuses on the removal of radionuclides, the stable elements in the reagents and apparatus are not of importance. Since the stable isotopes 99 Ru, 98 Ru, 100 Ru, 98 Mo, and 100 Mo are the main interferences in the mass spectrometric determination of 99 99 Tc has to be separated from the sample prior to irradiation; in addition a fast sample transfer system has to be used to shorten the decay time. NAA is theoretically a more sensitive method for 99 Tc, and a detection limit of 2.5 mBq has been obtained using pre-separation and radiochemical NAA [199][200].…”