Precise determination of femtogram quantities of radium by thermal ionization mass spectrometry

Abstract

Femtogram quantities of 22eRa (~3 X 10* atoms, or 4 X 10-3 Bq) have been determined In environmental materials, Including seawater, mineral samples, and silicate rocks, by thermal Ionization mass spectrometry. Chemical separation techniques suitable for all these materials are described here. Overall, these techniques enable the abundance of 22,Ra to be determined In samples of both seawater and silicates which are some 103 times smaller than those required by conventional radioactive counting methods.

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

“…These inherent effects limiting the capability of isotope ratio measurements by TIMS can be considered by different internal calibration techniques or by using isotopic standard reference materials with well-known isotopic ratios for an element. Besides, U, Th and Pu, TIMS has also been used for many other radionuclides, such as 41 Ca, 241 Am, 242 Cm, 126 Sn, 226 Ra, 228 Ra [82,[90][91][92][93].…”

“…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.…”

“…TIMS is a sensitive method for the determination of 226 Ra, a detection limit of 37 μBq was reported. While, detection limit of 12 mBq for 228 Ra is comparable to beta counting but worse than alpha counting using 228 Th [242,243]. The drawback of this method is the interference from Ba, which has to be completely separated from Ra.…”

“…Both the gamma emitting short-lived 239 Np (T½=2.35 d) and 235 Np (half-life of 396 days) may be used to trace the separation chemistry [262]. While 242 Pu is mainly used as tracer in many laboratories [259,263] because 242 Pu isotope is relatively close to 237 Np with respect to mass and ionization potential, can be obtained very pure (essentially free from 237 Np), and has a chemistry similar to that of plutonium.…”

“…During the last decade, the use of ICP-MS has gained a increased interest as an alternative to alpha spectrometry because of the good sensitivity, short analytical time and 239 Pu -240 Pu - 242 Pu isotopic information which are difficult to obtain through alpha spectrometry due either to overlapping peaks of 239 Pu at low levels (fg-pg range). Some of these are the relatively low abundance sensitivity, the risk of interferences from polyatomic species, blanks, background and sensitivity.…”