For analysis of environmental samples in the environmental sample laboratory (ESL) of SGAS (mostly swipe and hot cotton swipe samples), two categories are distinguished, low-level and high-level samples, with total 10 pg Pu and 1000 ng U considered to be high-level samples. After sample digestion and pre-screening, sample splitting is done followed by spiking with enriched <sup>242</sup>Pu, <sup>244</sup>Pu, <sup>233</sup>U and <sup>243</sup>Am spikes for isotope dilution analysis, using <sup>242</sup>Pu/Pu or <sup>244</sup>Pu/Pu amount ratios between 1 and 10, and <sup>233</sup>U/U of around 100. Spike solutions used are prepared by step-wise dilutions from mother solutions, and therefore the concentration needs to be corrected for evaporation loss during storage. U and Pu analysis is performed by MC-ICP-MS following the methods outlined in ref. 45,131 and 207.

ID-MS is performed on nuclear material samples by TIMS applying the total evaporation method.<sup>208,209</sup> After purification when needed,<sup>58</sup> appropriate amounts of uranium and plutonium solutions are deposited onto a filament for each measurement of safeguards samples, CRMs and process control materials. By making duplicate analyses of both the spiked aliquots and unspiked sample aliquots the isotopic composition and elemental concentrations can be calculated and compared with defined control and warning limits.

As an alternative to traditional ID-MS when both pure and spiked sample aliquots are measured by TIMS, a combination of techniques can be used. In the OSL, High Resolution Gamma Spectrometry (HRGS) is combined with TIMS to determine the isotopic composition<sup>210</sup> of samples that are subsequently subjected to spiking to perform the plutonium assay in pure plutonium solutions or mixed U and Pu solutions (free of strong beta gamma emitters, U/Pu ratio greater than two). For timeliness considerations, this method has the merit of skipping the chemical separation of the {sample-spike} fractions for isotope and ID analysis. In this case, values for isotope ratios of <sup>241</sup>Pu/<sup>239</sup>Pu and <sup>238</sup>Pu/<sup>239</sup>Pu in the ID-MS assay equation are replaced by ones obtained by HRGS Multi-Group Analysis Software (MGA) codes. For U containing samples with complex matrices and unknown declarations (also Pu materials containing traces of U), acceptable performance is achievable by using over-spiking (high spike-to-sample amounts) with highly enriched <sup>233</sup>U spikes to determine the uranium amount and isotopic composition of the material from TIMS measurements of spiked sample aliquots. This so-called isotope stripping approach has also been used for the determination of traces of U in Pu materials.<sup>211</sup>

## 5.4. Irradiated samples

Irradiated samples, for which ID-MS is commonly applied, typically originate from the nuclear fuel cycle (definition of NFC in ref. 212). Nuclear fuels, for generation of electricity in a Nuclear Power Plant (NPP), are based predominantly on uranium (e.g. uranium oxide (UOX) fuels) or mixtures of uranium with other elements (e.g. Pu in MOX fuels). The so-called major actinide elements, U and Pu, possess fertile isotopes. These are isotopes which can be converted into a fissile isotope by neutron absorption: for example, the <sup>238</sup>U isotope can be converted into <sup>239</sup>Pu or <sup>242</sup>Pu can be converted

into <sup>243</sup>Am. The major actinide elements also possess fissile isotopes, so it is possible that an actinide nucleus splits into two smaller nuclei, which are referred to as fission products: most of the lanthanides, cesium, and metallic fission products. Therefore, a nuclear fuel can contain a wide range of chemical elements once it has been irradiated. The isotopic composition of a fission product element can differ substantially from the naturally occurring isotopic composition of that same element: certain stable isotopes of an element might not be formed by fission. The amount of particular fission products (e.g. specific isotopes of Cs, Ce and Nd) present in an irradiated fuel can be very indicative of how much fission has taken place, and hence such isotopes can be used as fission burn-up monitors.<sup>213</sup> Information about the extent of fission in a particular fuel (rod) is very useful knowledge for the safe and correct operation of an NPP. In the case of non-power reactors, which are used for material testing, R&D, and training purposes for example, the trend to switch from highly enriched uranium (HEU) to low enriched uranium (LEU) fuels (an anti-proliferation measure) has involved the testing of a range of fuels that differ quite substantially, in chemical and physical form, and enrichment, from those used in NPPs. Irradiated samples received by a radiochemical analysis laboratory can therefore differ widely in terms of matrices, their chemical composition (oxide based fuels to metallic or silicide fuels) and homogeneity, their enrichment (from LEU to HEU), and their physical form (a segment from an oxide fuel or a segment from a plate fuel).

Despite the variety of irradiated samples, the determination of the U, Pu and Nd isotopic and elemental mass fractions by means of ID-MS can already provide considerable information. This is a common analysis as part of post irradiation examination. This gives information about the residual heavy metal atoms (the major actinides) and the concentration of the burn-up monitor (in this case the Nd fission product) can be used in the estimation of the fuel burn-up. Such information can be fed back into areas such as the assessment of fuel performance/qualification, validation of nuclear codes for criticality or for long-term storage of nuclear waste.<sup>31,38,130,214,215</sup> Crucially, these rely on the low measurement uncertainties ID-MS can provide.

The irradiated sample first has to be brought into solution, before spiking can occur. Dissolution of spent fuels for analysis is detailed elsewhere,<sup>216-221</sup> but in general terms an irradiated fuel is often dissolved quantitatively by heating (under reflux) under strong acidic conditions over several days inside a shelled hot cell. Only then can spikes be added to an aliquot of the dissolved sample, but crucially before any separations are started. Separations of lanthanides and actinides are discussed elsewhere.<sup>31-33,58,222-228</sup> Van Winckel et al.<sup>220</sup> provide a useful summary of the situations in which off-line and on-line separations are used for spent nuclear fuels.

Many practical details of the radiochemical analyses of the major actinides and Nd (amongst other actinides and fission products) to enable determination of the burn-up of an irradiated fuel are described elsewhere.<sup>229-232</sup> The methodology reported by Roach et al.<sup>231</sup> relies on on-line separation hyphenated to an MC-ICP-MS for isotopic vectors and Pu and Nd concentration or Davies & Gray titration for U concentration, all with

<figure><img src="image_29.png" /></figure>
For analysis of environmental samples in the environmental sample laboratory (ESL) of SGAS (mostly swipe and hot cotton swipe samples), two categories are distinguished, low-level and high-level samples, with total 10 pg Pu and 1000 ng U considered to be high-level samples. After sample digestion and pre-screening, sample splitting is done followed by spiking with enriched <sup>242</sup>Pu, <sup>244</sup>Pu, <sup>233</sup>U and <sup>243</sup>Am spikes for isotope dilution analysis, using <sup>242</sup>Pu/Pu or <sup>244</sup>Pu/Pu amount ratios between 1 and 10, and <sup>233</sup>U/U of around 100. Spike solutions used are prepared by step-wise dilutions from mother solutions, and therefore the concentration needs to be corrected for evaporation loss during storage. U and Pu analysis is performed by MC-ICP-MS following the methods outlined in ref. 45,131 and 207.

ID-MS is performed on nuclear material samples by TIMS applying the total evaporation method.<sup>208,209</sup> After purification when needed,<sup>58</sup> appropriate amounts of uranium and plutonium solutions are deposited onto a filament for each measurement of safeguards samples, CRMs and process control materials. By making duplicate analyses of both the spiked aliquots and unspiked sample aliquots the isotopic composition and elemental concentrations can be calculated and compared with defined control and warning limits.

As an alternative to traditional ID-MS when both pure and spiked sample aliquots are measured by TIMS, a combination of techniques can be used. In the OSL, High Resolution Gamma Spectrometry (HRGS) is combined with TIMS to determine the isotopic composition<sup>210</sup> of samples that are subsequently subjected to spiking to perform the plutonium assay in pure plutonium solutions or mixed U and Pu solutions (free of strong beta gamma emitters, U/Pu ratio greater than two). For timeliness considerations, this method has the merit of skipping the chemical separation of the {sample-spike} fractions for isotope and ID analysis. In this case, values for isotope ratios of <sup>241</sup>Pu/<sup>239</sup>Pu and <sup>238</sup>Pu/<sup>239</sup>Pu in the ID-MS assay equation are replaced by ones obtained by HRGS Multi-Group Analysis Software (MGA) codes. For U containing samples with complex matrices and unknown declarations (also Pu materials containing traces of U), acceptable performance is achievable by using over-spiking (high spike-to-sample amounts) with highly enriched <sup>233</sup>U spikes to determine the uranium amount and isotopic composition of the material from TIMS measurements of spiked sample aliquots. This so-called isotope stripping approach has also been used for the determination of traces of U in Pu materials.<sup>211</sup>

## 5.4. Irradiated samples

Irradiated samples, for which ID-MS is commonly applied, typically originate from the nuclear fuel cycle (definition of NFC in ref. 212). Nuclear fuels, for generation of electricity in a Nuclear Power Plant (NPP), are based predominantly on uranium (e.g. uranium oxide (UOX) fuels) or mixtures of uranium with other elements (e.g. Pu in MOX fuels). The so-called major actinide elements, U and Pu, possess fertile isotopes. These are isotopes which can be converted into a fissile isotope by neutron absorption: for example, the <sup>238</sup>U isotope can be converted into <sup>239</sup>Pu or <sup>242</sup>Pu can be converted

into <sup>243</sup>Am. The major actinide elements also possess fissile isotopes, so it is possible that an actinide nucleus splits into two smaller nuclei, which are referred to as fission products: most of the lanthanides, cesium, and metallic fission products. Therefore, a nuclear fuel can contain a wide range of chemical elements once it has been irradiated. The isotopic composition of a fission product element can differ substantially from the naturally occurring isotopic composition of that same element: certain stable isotopes of an element might not be formed by fission. The amount of particular fission products (e.g. specific isotopes of Cs, Ce and Nd) present in an irradiated fuel can be very indicative of how much fission has taken place, and hence such isotopes can be used as fission burn-up monitors.<sup>213</sup> Information about the extent of fission in a particular fuel (rod) is very useful knowledge for the safe and correct operation of an NPP. In the case of non-power reactors, which are used for material testing, R&D, and training purposes for example, the trend to switch from highly enriched uranium (HEU) to low enriched uranium (LEU) fuels (an anti-proliferation measure) has involved the testing of a range of fuels that differ quite substantially, in chemical and physical form, and enrichment, from those used in NPPs. Irradiated samples received by a radiochemical analysis laboratory can therefore differ widely in terms of matrices, their chemical composition (oxide based fuels to metallic or silicide fuels) and homogeneity, their enrichment (from LEU to HEU), and their physical form (a segment from an oxide fuel or a segment from a plate fuel).

Despite the variety of irradiated samples, the determination of the U, Pu and Nd isotopic and elemental mass fractions by means of ID-MS can already provide considerable information. This is a common analysis as part of post irradiation examination. This gives information about the residual heavy metal atoms (the major actinides) and the concentration of the burn-up monitor (in this case the Nd fission product) can be used in the estimation of the fuel burn-up. Such information can be fed back into areas such as the assessment of fuel performance/qualification, validation of nuclear codes for criticality or for long-term storage of nuclear waste.<sup>31,38,130,214,215</sup> Crucially, these rely on the low measurement uncertainties ID-MS can provide.

The irradiated sample first has to be brought into solution, before spiking can occur. Dissolution of spent fuels for analysis is detailed elsewhere,<sup>216-221</sup> but in general terms an irradiated fuel is often dissolved quantitatively by heating (under reflux) under strong acidic conditions over several days inside a shelled hot cell. Only then can spikes be added to an aliquot of the dissolved sample, but crucially before any separations are started. Separations of lanthanides and actinides are discussed elsewhere.<sup>31-33,58,222-228</sup> Van Winckel *et al.*<sup>220</sup> provide a useful summary of the situations in which off-line and on-line separations are used for spent nuclear fuels.

Many practical details of the radiochemical analyses of the major actinides and Nd (amongst other actinides and fission products) to enable determination of the burn-up of an irradiated fuel are described elsewhere.<sup>229-232</sup> The methodology reported by Roach *et al.*<sup>231</sup> relies on on-line separation hyphenated to an MC-ICP-MS for isotopic vectors and Pu and Nd concentration or Davies & Gray titration for U concentration, all with

<figure><img src="image_29.png" /></figure>
<figure><img src="image_30.png" /></figure>

calibration by ID-MS to provide results much more rapidly than off-line separations combined with an analytical technique such as TIMS.

The ASTM E321-20 method<sup>233</sup> uses the <sup>148</sup>Nd concentration as the fission burn-up monitor, due to the small difference between the fission yield of the two dominant fissile isotopes (<sup>235</sup>U and <sup>239</sup>Pu). Govers *et al.*<sup>234</sup> reported that this approach works well for NPPs, but that in high-flux reactors (non-power reactors) the <sup>147</sup>Nd(n)<sup>148</sup>Nd (i.e. short form for the <sup>147</sup>Nd + n → <sup>148</sup>Nd formula) capture reaction may no longer be insignificant. In such cases, a correction needs to be applied to avoid an overestimation of the burn-up when using the <sup>148</sup>Nd concentration. If it is not possible to correct the <sup>148</sup>Nd for such capture by <sup>147</sup>Nd an alternative is to measure the entire Nd vector. Data from the other Nd isotopes can provide estimates of the burn-up value.

The isotopic composition of stable or long-lived Nd isotopes formed during fission in irradiated fuels, including the absence of <sup>142</sup>Nd, differs from that of natural Nd. Data from almost 40 different irradiated fuel samples at the SCK laboratories indicate the isotopic abundances of <sup>146</sup>Nd and <sup>150</sup>Nd are rather similar to their natural abundances whilst those of <sup>145</sup>Nd and <sup>148</sup>Nd are approximately doubled. For <sup>143</sup>Nd and <sup>144</sup>Nd the abundances can deviate more widely from their natural isotopic abundances. Roach *et al.*<sup>231</sup> give examples of such data from three samples. The choice of the spike isotope for the quantification of Nd formed during fission is different than for Nd with natural isotopic composition due to their different isotopic compositions. A spike enriched in the <sup>146</sup>Nd isotope can be an alternative to <sup>148</sup>Nd and <sup>150</sup>Nd isotopes<sup>33,38</sup> if the entire Nd vector is to be measured. The amount of spike to be added depends on the concentration in the sample, and to some extent this depends on the laboratory's operating license. Some laboratories perform spiking inside a glovebox and others under a fumehood, the difference being the amount of U, Pu or Nd in the sample to be spiked. To perform spiking under a fumehood, an aliquot of diluted mother solution is required as the mother solution is too active, which in turn requires an appropriately lower spike concentration to avoid overspiking and to avoid spike masses with too high an uncertainty.

Cesium can also be used as an alternative fission burn-up monitor to neodymium.<sup>235-239</sup> After irradiation of the fuel, the sample contains <sup>133</sup>Cs, <sup>134</sup>Cs, <sup>135</sup>Cs and <sup>137</sup>Cs. Cesium is naturally monoisotopic (<sup>133</sup>Cs), which makes it a good spike for such sample. The difficulties of cesium measurement by ID-MS come from the lack of reference materials to estimate the mass fractionation. Different methods can be used, such as a combination of TIMS and gamma spectrometry or intertechnique comparison.<sup>235,240</sup>

## 5.5. Biological applications

Radionuclide analysis in biological samples became important considering their intensive use in industry and medicine, and for some of them, their natural presence in the environment, such as Th and U (also named NORM, for Naturally Occurring Radioactive Material). Therefore, monitoring human exposure

is crucial for evaluating the risks to the wider population and to workers. In addition, in case of a nuclear crisis or radiological exposure, such analyses are crucial to identify each individual's contamination. The most common matrices in which radionuclides are analyzed are urine and feces, but others biological tissues can also be considered in the research field.

The ICP-MS technique has become increasingly popular in recent years for measuring those radionuclides with a sufficiently long half-life ($t_{1/2} > 10\,000$ years).<sup>241</sup> The performance of ICP-MS, in terms of limits of detection and analysis time (several minutes), offers considerable advantages, even for complex matrices, over nuclear techniques such as alpha spectrometry.<sup>242,243</sup> Furthermore, in addition to activity concentration determination, the isotopic composition can be determined by means of ICP-MS, which enables the origin of a contamination to be traced.<sup>242,244</sup>

For urine samples, diluted samples can be measured directly by means of ICP-MS with external calibration, if their concentrations are high enough.<sup>245,246</sup> However, for urine samples with extremely low radionuclide concentrations and/or for other biological matrices such as feces, blood, nail and hair, a radiochemical purification and pre-concentration may be necessary before measurement by ICP-MS (urinary U,<sup>247,248</sup> urinary Pu<sup>249</sup>). The ID technique is, in this case, highly recommended: (i) to evaluate the chemical yield and (ii) to use as an internal standard to measure the concentrations accurately by means of ICP-MS. Therefore, ID coupled to ICP-MS permits proper characterization by more accurate matrix effect corrections in case of high matrix or low concentration measurements.

ICP-MS is widely used for actinide (U, Pu, Am) analyses of biological samples<sup>241,246,247,249-270</sup> with calibration methods that rely on an actinide isotope that is absent from the sample, such as <sup>233</sup>U for U isotopes (<sup>234</sup>U, <sup>235</sup>U, <sup>236</sup>U and <sup>238</sup>U), <sup>242</sup>Pu for Pu isotopes (<sup>239</sup>Pu, <sup>240</sup>Pu, and <sup>241</sup>Pu) or <sup>243</sup>Am for <sup>241</sup>Am analysis. Ni *et al.* developed a protocol for the rapid determination of ultra-trace plutonium isotopes in small volumes of urine.<sup>249</sup> This method is based on a chemical treatment of the urine samples (acid digestion, co-precipitation, extraction chromatography) before plutonium measurement by means of HR-ICP-MS. A <sup>242</sup>Pu spike is used as a yield tracer to characterize the Pu isotopes. The method allows a high <sup>238</sup>U decontamination factor ($3.8 \times 10^6$), which is essential to limit the polyatomic interference of <sup>238</sup>UH<sup>+</sup> during <sup>239</sup>Pu measurement. An average value of 72.7 ± 5.5% was achieved for <sup>242</sup>Pu recovery for 20 mL or 100 mL urine bioassays. For 100 mL urine samples, the limits of detection (LODs) of <sup>239</sup>Pu, <sup>240</sup>Pu and <sup>241</sup>Pu were 0.003 fg mL<sup>-1</sup>, 0.002 fg mL<sup>-1</sup>, and 0.003 fg mL<sup>-1</sup>, corresponding to 0.006 mBq L<sup>-1</sup>, 0.015 mBq L<sup>-1</sup> and 9.8 mBq L<sup>-1</sup>, respectively. The current LODs of <sup>239</sup>Pu and <sup>240</sup>Pu by means of ICP-MS are more than 100 times lower than those usually achieved by means of the alpha spectrometry method (1 mBq L<sup>-1</sup>). In another study, Wang *et al.* developed an online separation and pre-concentration method coupled with ICP-MS/MS for measurement of <sup>90</sup>Sr, <sup>234</sup>U, <sup>239</sup>Pu and <sup>241</sup>Am isotopes using <sup>233</sup>U, <sup>242</sup>Pu and <sup>86</sup>Sr tracers to correct for column recovery and matrix effects.<sup>271</sup> This method required small sample volumes (10 mL) and offered rapid analysis times (46 min per sample for the full
<figure><img src="image_30.png" /></figure>

calibration by ID-MS to provide results much more rapidly than off-line separations combined with an analytical technique such as TIMS.

The ASTM E321-20 method<sup>233</sup> uses the <sup>148</sup>Nd concentration as the fission burn-up monitor, due to the small difference between the fission yield of the two dominant fissile isotopes (<sup>235</sup>U and <sup>239</sup>Pu). Govers *et al.*<sup>234</sup> reported that this approach works well for NPPs, but that in high-flux reactors (non-power reactors) the <sup>147</sup>Nd(n)<sup>148</sup>Nd (i.e. short form for the <sup>147</sup>Nd + n → <sup>148</sup>Nd formula) capture reaction may no longer be insignificant. In such cases, a correction needs to be applied to avoid an overestimation of the burn-up when using the <sup>148</sup>Nd concentration. If it is not possible to correct the <sup>148</sup>Nd for such capture by <sup>147</sup>Nd an alternative is to measure the entire Nd vector. Data from the other Nd isotopes can provide estimates of the burn-up value.

The isotopic composition of stable or long-lived Nd isotopes formed during fission in irradiated fuels, including the absence of <sup>142</sup>Nd, differs from that of natural Nd. Data from almost 40 different irradiated fuel samples at the SCK laboratories indicate the isotopic abundances of <sup>146</sup>Nd and <sup>150</sup>Nd are rather similar to their natural abundances whilst those of <sup>145</sup>Nd and <sup>148</sup>Nd are approximately doubled. For <sup>143</sup>Nd and <sup>144</sup>Nd the abundances can deviate more widely from their natural isotopic abundances. Roach *et al.*<sup>231</sup> give examples of such data from three samples. The choice of the spike isotope for the quantification of Nd formed during fission is different than for Nd with natural isotopic composition due to their different isotopic compositions. A spike enriched in the <sup>146</sup>Nd isotope can be an alternative to <sup>148</sup>Nd and <sup>150</sup>Nd isotopes<sup>33,38</sup> if the entire Nd vector is to be measured. The amount of spike to be added depends on the concentration in the sample, and to some extent this depends on the laboratory's operating license. Some laboratories perform spiking inside a glovebox and others under a fumehood, the difference being the amount of U, Pu or Nd in the sample to be spiked. To perform spiking under a fumehood, an aliquot of diluted mother solution is required as the mother solution is too active, which in turn requires an appropriately lower spike concentration to avoid overspiking and to avoid spike masses with too high an uncertainty.

Cesium can also be used as an alternative fission burn-up monitor to neodymium.<sup>235-239</sup> After irradiation of the fuel, the sample contains <sup>133</sup>Cs, <sup>134</sup>Cs, <sup>135</sup>Cs and <sup>137</sup>Cs. Cesium is naturally monoisotopic (<sup>133</sup>Cs), which makes it a good spike for such sample. The difficulties of cesium measurement by ID-MS come from the lack of reference materials to estimate the mass fractionation. Different methods can be used, such as a combination of TIMS and gamma spectrometry or intertechnique comparison.<sup>235,240</sup>

## 5.5. Biological applications

Radionuclide analysis in biological samples became important considering their intensive use in industry and medicine, and for some of them, their natural presence in the environment, such as Th and U (also named NORM, for Naturally Occurring Radioactive Material). Therefore, monitoring human exposure

is crucial for evaluating the risks to the wider population and to workers. In addition, in case of a nuclear crisis or radiological exposure, such analyses are crucial to identify each individual's contamination. The most common matrices in which radionuclides are analyzed are urine and feces, but others biological tissues can also be considered in the research field.

The ICP-MS technique has become increasingly popular in recent years for measuring those radionuclides with a sufficiently long half-life ($t_{1/2} > 10\,000$ years).<sup>241</sup> The performance of ICP-MS, in terms of limits of detection and analysis time (several minutes), offers considerable advantages, even for complex matrices, over nuclear techniques such as alpha spectrometry.<sup>242,243</sup> Furthermore, in addition to activity concentration determination, the isotopic composition can be determined by means of ICP-MS, which enables the origin of a contamination to be traced.<sup>242,244</sup>

For urine samples, diluted samples can be measured directly by means of ICP-MS with external calibration, if their concentrations are high enough.<sup>245,246</sup> However, for urine samples with extremely low radionuclide concentrations and/or for other biological matrices such as feces, blood, nail and hair, a radiochemical purification and pre-concentration may be necessary before measurement by ICP-MS (urinary U,<sup>247,248</sup> urinary Pu<sup>249</sup>). The ID technique is, in this case, highly recommended: (i) to evaluate the chemical yield and (ii) to use as an internal standard to measure the concentrations accurately by means of ICP-MS. Therefore, ID coupled to ICP-MS permits proper characterization by more accurate matrix effect corrections in case of high matrix or low concentration measurements.

ICP-MS is widely used for actinide (U, Pu, Am) analyses of biological samples<sup>241,246,247,249-270</sup> with calibration methods that rely on an actinide isotope that is absent from the sample, such as <sup>233</sup>U for U isotopes (<sup>234</sup>U, <sup>235</sup>U, <sup>236</sup>U and <sup>238</sup>U), <sup>242</sup>Pu for Pu isotopes (<sup>239</sup>Pu, <sup>240</sup>Pu, and <sup>241</sup>Pu) or <sup>243</sup>Am for <sup>241</sup>Am analysis. Ni *et al.* developed a protocol for the rapid determination of ultra-trace plutonium isotopes in small volumes of urine.<sup>249</sup> This method is based on a chemical treatment of the urine samples (acid digestion, co-precipitation, extraction chromatography) before plutonium measurement by means of HR-ICP-MS. A <sup>242</sup>Pu spike is used as a yield tracer to characterize the Pu isotopes. The method allows a high <sup>238</sup>U decontamination factor ($3.8 \times 10^6$), which is essential to limit the polyatomic interference of <sup>238</sup>UH<sup>+</sup> during <sup>239</sup>Pu measurement. An average value of 72.7 ± 5.5% was achieved for <sup>242</sup>Pu recovery for 20 mL or 100 mL urine bioassays. For 100 mL urine samples, the limits of detection (LODs) of <sup>239</sup>Pu, <sup>240</sup>Pu and <sup>241</sup>Pu were 0.003 fg mL<sup>-1</sup>, 0.002 fg mL<sup>-1</sup>, and 0.003 fg mL<sup>-1</sup>, corresponding to 0.006 mBq L<sup>-1</sup>, 0.015 mBq L<sup>-1</sup> and 9.8 mBq L<sup>-1</sup>, respectively. The current LODs of <sup>239</sup>Pu and <sup>240</sup>Pu by means of ICP-MS are more than 100 times lower than those usually achieved by means of the alpha spectrometry method (1 mBq L<sup>-1</sup>). In another study, Wang *et al.* developed an online separation and pre-concentration method coupled with ICP-MS/MS for measurement of <sup>90</sup>Sr, <sup>234</sup>U, <sup>239</sup>Pu and <sup>241</sup>Am isotopes using <sup>233</sup>U, <sup>242</sup>Pu and <sup>86</sup>Sr tracers to correct for column recovery and matrix effects.<sup>271</sup> This method required small sample volumes (10 mL) and offered rapid analysis times (46 min per sample for the full
process) and was applied to various liquid matrices (lake water, seawater, and urine samples). The limits of detection were 1.48 pg L⁻¹ (8257 mBq L⁻¹) for ⁹⁰Sr, 1.75 pg L⁻¹ (0.40 mBq L⁻¹) for ²³⁴U, 0.65 pg L⁻¹ (77.65 mBq L⁻¹) for ²⁴¹Am, and 0.56 pg L⁻¹ (1.25 mBq L⁻¹) for ²³⁹Pu. In this work, no specific spike was used for ²⁴¹Am analysis. The authors mentioned that high recoveries were obtained for ²⁴¹Am in samples analyzed by means of this protocol. Therefore, it may be suspected that no recovery correction was applied for the determination of ²⁴¹Am. To a limited extent, spike addition has been used to trace another radioelement, e.g. the use of ²⁴²Pu to trace ²³⁷Np, for which no suitable tracer is available, during quantification of ²³⁷Np by means of ICP-MS.²⁵⁴ In this study, the authors showed that ²⁴²Pu can serve as the recovery monitor for ²³⁷Np in the separation and pre-concentration procedure developed.

It should be noted that, in all these publications, no ID equation was detailed. Furthermore, the use of spikes is often mentioned in these papers as a yield tracer. Consequently, it may be suspected that these spikes are used more as internal tracers for recovery correction than as spikes for ID.

Clases et al.²⁷² suggested an “isobaric dilution analysis” (IBDA) method as a “new quantitative method for long-lived radionuclides” by means of ICP-MS. The technique relies on using a spike of a different element, but which contains an isobaric isotope and has similar chemical properties to those of the analyte. Demonstration of IBDA has been performed on the determination of gadolinium concentration using a certified dysprosium solution spike by measuring the ¹⁵⁷Gd/¹⁶⁰Dy ratio. The same authors applied IBDA for technetium, for which no safe standard, in terms of radioprotection, is available. They demonstrated that the IBDA technique can also be applied on an element with monoisotopic abundance such as ⁹⁹Tc using a ruthenium solution as a spike solution. The determination of ⁹⁹Tc in the ⁹⁹Tc-MAG3 drug is therefore obtained using the ⁹⁹Tc/¹⁰¹Ru ratio. This technique could be extended to ⁴¹Ca, ⁶⁰Co and ⁹⁰Sr using K, Ni and Zr, respectively and applied in various application fields such as industry, environment, cosmochemistry and medicine.²⁷²

Furthermore, understanding the behavior, biokinetics and excretion of radionuclides from the human body increases even more in priority due to the increase of their medical applications. Therefore, radionuclide quantification by ID-ICP-MS is a promising tool for investigating the partitioning and behavior of radionuclides in organ tissues, such as the use of ²⁴²Pu and ²⁴³Am spikes to determine ²³⁹Pu, ²⁴⁰Pu and ²⁴¹Am isotopes in brain tissues.²⁷³

Enriched spikes have also been used to trace specific speciation into the organism.⁴⁷ However, this technique has not yet been applied to radionuclides.

ID-MS is a promising technique for quantifying low radio-nuclide concentration and/or in complex matrices for radiation protection purposes and also for investigating the behavior of radionuclides in biological tissues. However, this technique has not been used widely with well-described ID equations. This is perhaps due to the limited number of laboratories performing radioisotope quantification in biological samples by means of ICP-MS. Nevertheless, developments in ID-MS can be anticipated in the coming years.

## 5.6. Reference material

For CRM certification, reference measurement techniques that provide metrological traceability are required. ID-MS is a very accurate technique for the determination of element mass fraction and provides results with low uncertainties: it can be applied as a primary ratio method when suitable CRMs and calibrators are available. The challenges associated with the development of reference measurement systems for clinical analytes, and in particular for ID-MS, are highlighted in ref. 274. The role of ID-MS in the certification of CRMs is presented in ref. 20 and 21. ID-MS is commonly used by nuclear CRM producers either for characterization or for verification of the assigned certified values determined by means of other techniques.⁴³,⁵⁶,⁷¹,²⁰¹ Facility operator laboratories and other laboratories performing nuclear material analyses use ID-MS for the characterization of laboratory CRMs for quality management, process or instrument control and preparation of spikes.⁸⁶,²⁰¹,²⁷⁵ ID-MS was used in the last few years to certify several CRMs: ²⁴³Am spike,⁷,⁵⁶,²⁷⁶ LSD spike,⁷³,²⁰¹ ²²⁹Th spike,³⁶ ²³¹Pa spike,¹⁵⁶ ²⁴²Pu spike,²⁷⁷ ²⁴⁴Pu spike⁴³ or uranium oxide particle CRM.²⁷⁸

On the other hand, CRMs play a crucial role in the performance of ID-MS measurements. Using high quality CRMs in ID-MS provides accurate and traceable measurement results. For instance, in nuclear safeguards spikes are a metrological quality tool to meet the existing requirements indicated by the ITVs for reliable accountancy and verification measurements.²⁴,²⁵ Considering modern instrumentation and state-of-the-practice methods, uncertainties of the CRM isotope ratios often significantly dominate the uncertainty budgets for the assay values of U and Pu. Several studies conducted by the IAEA for evaluating the fitness for purpose of CRMs in use²⁷⁹ have concluded that the certified uncertainties of some CRMs were larger than the estimated intermediate precision of the TIMS measurements. Thus, the need for re-certification for better uncertainty is to be addressed by CRM producers. For this important metrology mission, the IAEA and the JRC-Geel organize technical meetings among the safeguards community to discuss the current requirements of the CRMs.

## 5.7. Process control

ID is a method of choice for process control applications that require an especially high accuracy, granted that appropriate spikes are available for the measured elements. ID comes with a significant advantage over almost all other methods, as it is not affected by sample losses, as long as the loss occurs after the preparation of the {sample-spike} mixture. This is a great feature of ID for trace and ultra-trace analysis that is very sensitive to any sample loss during preparation steps such as separation, dilution, evaporation, etc. Another actual advantage of ID is its very low sensitivity to matrix effects, because the spike and sample both share the same matrix and valency after mixture homogenization.

However, it comes with a rather complex setup that complicates and extends the sample preparation, which may be an issue for routine analysis. This is mainly due to the spiking step, where each sample is carefully spiked with an accurately

<figure><img src="image_31.png" /></figure>
<figure><img src="image_31.png" /></figure>

process) and was applied to various liquid matrices (lake water, seawater, and urine samples). The limits of detection were 1.48 pg L⁻¹ (8257 mBq L⁻¹) for ⁹⁰Sr, 1.75 pg L⁻¹ (0.40 mBq L⁻¹) for ²³⁴U, 0.65 pg L⁻¹ (77.65 mBq L⁻¹) for ²⁴¹Am, and 0.56 pg L⁻¹ (1.25 mBq L⁻¹) for ²³⁹Pu. In this work, no specific spike was used for ²⁴¹Am analysis. The authors mentioned that high recoveries were obtained for ²⁴¹Am in samples analyzed by means of this protocol. Therefore, it may be suspected that no recovery correction was applied for the determination of ²⁴¹Am. To a limited extent, spike addition has been used to trace another radioelement, e.g. the use of ²⁴²Pu to trace ²³⁷Np, for which no suitable tracer is available, during quantification of ²³⁷Np by means of ICP-MS.²⁵⁴ In this study, the authors showed that ²⁴²Pu can serve as the recovery monitor for ²³⁷Np in the separation and pre-concentration procedure developed.

It should be noted that, in all these publications, no ID equation was detailed. Furthermore, the use of spikes is often mentioned in these papers as a yield tracer. Consequently, it may be suspected that these spikes are used more as internal tracers for recovery correction than as spikes for ID.

Clases et al.²⁷² suggested an "isobaric dilution analysis" (IBDA) method as a "new quantitative method for long-lived radionuclides" by means of ICP-MS. The technique relies on using a spike of a different element, but which contains an isobaric isotope and has similar chemical properties to those of the analyte. Demonstration of IBDA has been performed on the determination of gadolinium concentration using a certified dysprosium solution spike by measuring the ¹⁵⁷Gd/¹⁶⁰Dy ratio. The same authors applied IBDA for technetium, for which no safe standard, in terms of radioprotection, is available. They demonstrated that the IBDA technique can also be applied on an element with monoisotopic abundance such as ⁹⁹Tc using a ruthenium solution as a spike solution. The determination of ⁹⁹Tc in the ⁹⁹Tc-MAG3 drug is therefore obtained using the ⁹⁹Tc/¹⁰¹Ru ratio. This technique could be extended to ⁴¹Ca, ⁶⁰Co and ⁹⁰Sr using K, Ni and Zr, respectively and applied in various application fields such as industry, environment, cosmochemistry and medicine.²⁷²

Furthermore, understanding the behavior, biokinetics and excretion of radionuclides from the human body increases even more in priority due to the increase of their medical applications. Therefore, radionuclide quantification by ID-ICP-MS is a promising tool for investigating the partitioning and behavior of radionuclides in organ tissues, such as the use of ²⁴²Pu and ²⁴³Am spikes to determine ²³⁹Pu, ²⁴⁰Pu and ²⁴¹Am isotopes in brain tissues.²⁷³

Enriched spikes have also been used to trace specific speciation into the organism.⁴⁷ However, this technique has not yet been applied to radionuclides.

ID-MS is a promising technique for quantifying low radio-nuclide concentration and/or in complex matrices for radiation protection purposes and also for investigating the behavior of radionuclides in biological tissues. However, this technique has not been used widely with well-described ID equations. This is perhaps due to the limited number of laboratories performing radioisotope quantification in biological samples by means of ICP-MS. Nevertheless, developments in ID-MS can be anticipated in the coming years.

## 5.6. Reference material

For CRM certification, reference measurement techniques that provide metrological traceability are required. ID-MS is a very accurate technique for the determination of element mass fraction and provides results with low uncertainties: it can be applied as a primary ratio method when suitable CRMs and calibrators are available. The challenges associated with the development of reference measurement systems for clinical analytes, and in particular for ID-MS, are highlighted in ref. 274. The role of ID-MS in the certification of CRMs is presented in ref. 20 and 21. ID-MS is commonly used by nuclear CRM producers either for characterization or for verification of the assigned certified values determined by means of other techniques.⁴³,⁵⁶,⁷¹,²⁰¹ Facility operator laboratories and other laboratories performing nuclear material analyses use ID-MS for the characterization of laboratory CRMs for quality management, process or instrument control and preparation of spikes.⁸⁶,²⁰¹,²⁷⁵ ID-MS was used in the last few years to certify several CRMs: ²⁴³Am spike, ⁷,⁵⁶,²⁷⁶ LSD spike, ⁷³,²⁰¹ ²²⁹Th spike, ⁶⁶ ²³¹Pa spike, ¹⁵⁶ ²⁴²Pu spike, ²⁷⁷ ²⁴⁴Pu spike⁴³ or uranium oxide particle CRM.²⁷⁸

On the other hand, CRMs play a crucial role in the performance of ID-MS measurements. Using high quality CRMs in ID-MS provides accurate and traceable measurement results. For instance, in nuclear safeguards spikes are a metrological quality tool to meet the existing requirements indicated by the ITVs for reliable accountancy and verification measurements.²⁴,²⁵ Considering modern instrumentation and state-of-the-practice methods, uncertainties of the CRM isotope ratios often significantly dominate the uncertainty budgets for the assay values of U and Pu. Several studies conducted by the IAEA for evaluating the fitness for purpose of CRMs in use²⁷⁹ have concluded that the certified uncertainties of some CRMs were larger than the estimated intermediate precision of the TIMS measurements. Thus, the need for re-certification for better uncertainty is to be addressed by CRM producers. For this important metrology mission, the IAEA and the JRC-Geel organize technical meetings among the safeguards community to discuss the current requirements of the CRMs.

## 5.7. Process control

ID is a method of choice for process control applications that require an especially high accuracy, granted that appropriate spikes are available for the measured elements. ID comes with a significant advantage over almost all other methods, as it is not affected by sample losses, as long as the loss occurs after the preparation of the {sample-spike} mixture. This is a great feature of ID for trace and ultra-trace analysis that is very sensitive to any sample loss during preparation steps such as separation, dilution, evaporation, etc. Another actual advantage of ID is its very low sensitivity to matrix effects, because the spike and sample both share the same matrix and valency after mixture homogenization.

However, it comes with a rather complex setup that complicates and extends the sample preparation, which may be an issue for routine analysis. This is mainly due to the spiking step, where each sample is carefully spiked with an accurately
weighed amount of spike. Automated systems based on highly accurate volumetric dispensers have been developed to solve this issue, helping to prepare a definite number of containers loaded with a known, accurately weighed amount of spike.²⁸⁰ These automated systems are particularly effective for process control, where the analyst has generally access to a decent estimation of expected sample concentrations.

For applications where speciation is important, various reports have demonstrated the compatibility of the ID method with techniques such as laser ablation (LA)-ICP-MS, gas chromatography (GC)-MS, high-performance liquid chromatography (HPLC)-ICP-MS, gamma spectrometry, etc.²⁸¹⁻²⁸⁵

## 6. Inter-laboratory comparisons involving ID-MS

ILCs can be divided into three categories: those involving expert laboratories participating in the certification of a CRM (such as that organized for STAM CRM ²⁴³Am certification²⁷⁶), those involving laboratories validating a new measurement method, and finally those testing the proficiency of laboratories/methods for measurement (Proficiency Test, PT). These last two types of ILC are efficient tools to monitor the quality of measurement of analytical laboratories and, in particular, for those using ID-MS. Usually, PTs are organized on a regular basis to evaluate the ability of the laboratory to measure one or several quantities called measurands.²⁸⁶ PTs also play an important role in a laboratory quality system and are increasingly recognized by national accreditation bodies and are part of the ISO17025 standard requirements for the competence of analytical laboratories.²⁸⁷ The benefit for a laboratory of participating in PTs is to evaluate the accuracy of its measurements and to take corrective actions if necessary. The evaluation procedure consists of providing performance scores, such as the z-score or the zeta-score.

The z-score (eqn (35)) compares the difference between the laboratory measurement result ($y_{lab}$) and the PT assigned value ($y_{PT}$, certified or consensual value) to the PT standard deviation ($S_{PT}$, usually determined by robust statistics).

$$z\text{-score} = \frac{y_{\text{lab}} - y_{\text{PT}}}{S_{\text{PT}}} \quad (35)$$

The zeta-score compares the same numerator to the uncertainty of the difference between the laboratory measurement value ($u_{lab}$) and assigned value ($u_{PT}$, eqn (36)).

$$\text{zeta-score} = \frac{y_{\text{lab}} - y_{\text{PT}}}{\sqrt{u_{\text{lab}}^2 + u_{\text{PT}}^2}} \quad (36)$$

According to z or zeta-score values, results are classified as:

- Satisfactory if $|z|$ or $|zeta| < 2$.

- Questionable if $2 < |z|$ or $|zeta| < 3$.

- Unsatisfactory if $|z|$ or $|zeta| > 3$.

The z-score indicates the number of PT standard deviations between the laboratory measurement value and the PT assigned value. The zeta-score determines whether the measurement

uncertainty value claimed by the laboratory allows the laboratory's measurement value and the assigned value to be considered identical. Action is then encouraged if unsatisfactory performance is indicated.

In the field of radionuclide analysis, several international PTs are organized annually by different institutions (IAEA, CETAMA, NBL, JRC, etc.) in different fields ranging from environmental concerns to safeguards or nuclear mining/enrichment/reprocessing activities.

Laboratories using ID techniques are generally concerned with PTs for the measurement of radionuclide mass fractions (or amount content) in solids or solutions. For example, CETAMA offers PTs, called EQRAIN U, EQRAIN Pu and EQRAIN (U + Pu), for the determination of U or/and Pu mass fractions in solution. These PTs are typically organized every 18 months.²³ The content values lie in the ranges of 1 to 6 g kg⁻¹ for Pu and 50 to 200 g kg⁻¹ for U, and are designed for laboratories connected with the mining or reprocessing industries, institutions for safeguards or institutions dealing with reference materials.

The IAEA regularly organizes NMRO Ro PTs and ILCs to assist the members of the IAEA network analytical laboratories (NWAL), as well as nuclear facility operators and other relevant laboratories, in the assessment of their nuclear material analyses (PTs) and environmental sample analyses (ILCs). During the last two exercises, the goal of NMRO Ro was to determine uranium mass and uranium isotopic ratios in uranium oxide powder, and uranium and plutonium masses and uranium and plutonium isotopic ratios in a dried mixed Pu-U nitrate sample.²⁸⁸ The goals of another ILC organized by the IAEA every two years are to measure the uranium and plutonium masses and isotopic abundances in cotton wipe samples (referred to as “swipe sample”) thanks to “bulk analysis” methods (swipe dissolution, uranium and plutonium purifications and ID-MS measurements).

## 7. Conclusion

This article reviews isotope dilution analysis and its application for radionuclide measurements in different contexts. ID-MS is a primary ratio method that helps to measure radionuclide mass fraction, in solids or liquids, with high accuracy. The ID-MS analysis process is well understood and the ID-MS measurement uncertainty is well controlled and quantified. An uncertainty estimation is calculated considering all stages in the ID-MS process. MCM or quadratic cumulation methods can be used for uncertainty calculation: both approaches yield identical results. To obtain the most accurate measurement, implementation is needed for all stages: weighing process, mixture preparation, spike monitoring, isotopic homogenization, and mass spectrometry measurements.

The excellent performance of ID-MS for radionuclide characterization has been demonstrated in a wide variety of fields: environmental, biological analysis, irradiated sample characterization, certified reference material production, safeguards and nuclear forensics. The ability to evaluate ID-MS measurement performance by using a wide range of ILCs is essential for guaranteeing measurement reliability and demonstrates that

<figure><img src="image_32.png" /></figure>
weighed amount of spike. Automated systems based on highly accurate volumetric dispensers have been developed to solve this issue, helping to prepare a definite number of containers loaded with a known, accurately weighed amount of spike.²⁸⁰ These automated systems are particularly effective for process control, where the analyst has generally access to a decent estimation of expected sample concentrations.

For applications where speciation is important, various reports have demonstrated the compatibility of the ID method with techniques such as laser ablation (LA)-ICP-MS, gas chromatography (GC)-MS, high-performance liquid chromatography (HPLC)-ICP-MS, gamma spectrometry, etc.²⁸¹⁻²⁸⁵

## 6. Inter-laboratory comparisons involving ID-MS

ILCs can be divided into three categories: those involving expert laboratories participating in the certification of a CRM (such as that organized for STAM CRM ²⁴³Am certification²⁷⁶), those involving laboratories validating a new measurement method, and finally those testing the proficiency of laboratories/methods for measurement (Proficiency Test, PT). These last two types of ILC are efficient tools to monitor the quality of measurement of analytical laboratories and, in particular, for those using ID-MS. Usually, PTs are organized on a regular basis to evaluate the ability of the laboratory to measure one or several quantities called measurands.²⁸⁶ PTs also play an important role in a laboratory quality system and are increasingly recognized by national accreditation bodies and are part of the ISO17025 standard requirements for the competence of analytical laboratories.²⁸⁷ The benefit for a laboratory of participating in PTs is to evaluate the accuracy of its measurements and to take corrective actions if necessary. The evaluation procedure consists of providing performance scores, such as the z-score or the zeta-score.

The z-score (eqn (35)) compares the difference between the laboratory measurement result ($y_{lab}$) and the PT assigned value ($y_{PT}$, certified or consensual value) to the PT standard deviation ($S_{PT}$, usually determined by robust statistics).

$$z\text{-score} = \frac{y_{\text{lab}} - y_{\text{PT}}}{S_{\text{PT}}} \qquad (35)$$

The zeta-score compares the same numerator to the uncertainty of the difference between the laboratory measurement value ($u_{lab}$) and assigned value ($u_{PT}$, eqn (36)).

$$\text{zeta-score} = \frac{y_{\text{lab}} - y_{\text{PT}}}{\sqrt{u_{\text{lab}}^2 + u_{\text{PT}}^2}} \qquad (36)$$

According to z or zeta-score values, results are classified as:

- Satisfactory if $|z|$ or $|zeta| < 2$.

- Questionable if $2 < |z|$ or $|zeta| < 3$.

- Unsatisfactory if $|z|$ or $|zeta| > 3$.

The z-score indicates the number of PT standard deviations between the laboratory measurement value and the PT assigned value. The zeta-score determines whether the measurement

uncertainty value claimed by the laboratory allows the laboratory's measurement value and the assigned value to be considered identical. Action is then encouraged if unsatisfactory performance is indicated.

In the field of radionuclide analysis, several international PTs are organized annually by different institutions (IAEA, CETAMA, NBL, JRC, etc.) in different fields ranging from environmental concerns to safeguards or nuclear mining/enrichment/reprocessing activities.

Laboratories using ID techniques are generally concerned with PTs for the measurement of radionuclide mass fractions (or amount content) in solids or solutions. For example, CETAMA offers PTs, called EQRAIN U, EQRAIN Pu and EQRAIN (U + Pu), for the determination of U or/and Pu mass fractions in solution. These PTs are typically organized every 18 months.²³ The content values lie in the ranges of 1 to 6 g kg⁻¹ for Pu and 50 to 200 g kg⁻¹ for U, and are designed for laboratories connected with the mining or reprocessing industries, institutions for safeguards or institutions dealing with reference materials.

The IAEA regularly organizes NMRO Ro PTs and ILCs to assist the members of the IAEA network analytical laboratories (NWAL), as well as nuclear facility operators and other relevant laboratories, in the assessment of their nuclear material analyses (PTs) and environmental sample analyses (ILCs). During the last two exercises, the goal of NMRO Ro was to determine uranium mass and uranium isotopic ratios in uranium oxide powder, and uranium and plutonium masses and uranium and plutonium isotopic ratios in a dried mixed Pu-U nitrate sample.²⁸⁸ The goals of another ILC organized by the IAEA every two years are to measure the uranium and plutonium masses and isotopic abundances in cotton wipe samples (referred to as "swipe sample") thanks to "bulk analysis" methods (swipe dissolution, uranium and plutonium purifications and ID-MS measurements).

## 7. Conclusion

This article reviews isotope dilution analysis and its application for radionuclide measurements in different contexts. ID-MS is a primary ratio method that helps to measure radionuclide mass fraction, in solids or liquids, with high accuracy. The ID-MS analysis process is well understood and the ID-MS measurement uncertainty is well controlled and quantified. An uncertainty estimation is calculated considering all stages in the ID-MS process. MCM or quadratic cumulation methods can be used for uncertainty calculation: both approaches yield identical results. To obtain the most accurate measurement, implementation is needed for all stages: weighing process, mixture preparation, spike monitoring, isotopic homogenization, and mass spectrometry measurements.

The excellent performance of ID-MS for radionuclide characterization has been demonstrated in a wide variety of fields: environmental, biological analysis, irradiated sample characterization, certified reference material production, safeguards and nuclear forensics. The ability to evaluate ID-MS measurement performance by using a wide range of ILCs is essential for guaranteeing measurement reliability and demonstrates that

<figure><img src="image_32.png" /></figure>
ID-MS has the potential to satisfy current and future needs in radioanalytical chemistry.

List of acronyms

<table><tr><td>CAB</td><td>Cellulose Acetate Butyrate</td></tr><tr><td>CCQM</td><td>Consultative Committee for Amount of Substance</td></tr><tr><td>CEA</td><td>French Alternative Energy and Atomic Energy Commission</td></tr><tr><td>CETAMA</td><td>Commission for the Establishment of Analytical Methods</td></tr><tr><td>CMC</td><td>CarboxyMethyl Cellulose sodium salt</td></tr><tr><td>CRM</td><td>Certified Reference Material</td></tr><tr><td>F</td><td>Error Multiplication Factor</td></tr><tr><td>HEU</td><td>Highly Enriched Uranium</td></tr><tr><td>HKED</td><td>Hybrid K-Edge Densitometry</td></tr><tr><td>HRGS</td><td>High Resolution Gamma Spectrometry</td></tr><tr><td>HR-ICP-MS</td><td>High Resolution-Inductively Coupled Plasma Mass Spectrometry</td></tr><tr><td>HU-1</td><td>Harwell Uraninite</td></tr><tr><td>IAEA</td><td>International Atomic Energy Agency</td></tr><tr><td>IBDA</td><td>Isobaric Dilution Analysis</td></tr><tr><td>ICP-MS</td><td>Inductively Coupled Plasma Mass Spectrometry</td></tr><tr><td>ID</td><td>Isotope Dilution</td></tr><tr><td>ID-MS</td><td>Isotope Dilution Mass Spectrometry</td></tr><tr><td>ILCs</td><td>Inter-Laboratory Comparisons</td></tr><tr><td>IRSN</td><td>French Institute for Radiation Protection and Nuclear Safety</td></tr><tr><td>ITVs</td><td>International Target Values</td></tr><tr><td>JAEA</td><td>Japan Atomic Energy Agency</td></tr><tr><td>JRC</td><td>Joint Research Centre</td></tr><tr><td>LAAT</td><td>Atalante Analysis Laboratory</td></tr><tr><td>LEU</td><td>Low Enriched Uranium</td></tr><tr><td>LOD</td><td>Limit Of Detection</td></tr><tr><td>LSD</td><td>Large-Sized Dried</td></tr><tr><td>MC-ICP-MS</td><td>Multi-Collector-Inductively Coupled Plasma Mass Spectrometry</td></tr><tr><td>MCM</td><td>Monte Carlo Method</td></tr><tr><td>MOX</td><td>Mixed OXide</td></tr><tr><td>MPE</td><td>Maximum Permissible Deviation</td></tr><tr><td>MSSP</td><td>Member States Support Programme</td></tr><tr><td>MGA</td><td>Multi-Group Analysis</td></tr><tr><td>NBL</td><td>New Brunswick Laboratory</td></tr><tr><td>NFC</td><td>Nuclear Fuel Cycle</td></tr><tr><td>NIST</td><td>National Institute of Standards and Technology</td></tr><tr><td>NMRoRo</td><td>Nuclear Material Round Robin</td></tr><tr><td>NORM</td><td>Naturally Occurring Radioactive Material</td></tr><tr><td>NPL</td><td>National Physical Laboratory</td></tr><tr><td>NPP</td><td>Nuclear Power Plant</td></tr><tr><td>NWAL</td><td>IAEA Network Analytical Laboratories</td></tr><tr><td>OSL</td><td>On-Site Laboratory</td></tr><tr><td>PT</td><td>Proficiency Test</td></tr><tr><td>R</td><td>Isotope Ratio</td></tr><tr><td>SCK</td><td>Belgian Nuclear Research Centre</td></tr><tr><td>SGAS</td><td>Office of Safeguards Analytical Services</td></tr><tr><td>SGAS-ESL</td><td>Environmental Sample Laboratory of SGAS</td></tr></table>

<table><tr><td>SGAS</td><td>Nuclear Material Laboratory of SGAS</td></tr><tr><td>NML</td><td></td></tr><tr><td>SI</td><td>International System of Units</td></tr><tr><td>SRM</td><td>Standard Reference Material</td></tr><tr><td>t<sub>1/2</sub></td><td>Half-life</td></tr><tr><td>TIMS</td><td>Thermal Ionization Mass Spectrometry</td></tr><tr><td>u</td><td>Standard Uncertainty</td></tr><tr><td>UOX</td><td>Uranium Oxide</td></tr><tr><td>u<sub>r</sub></td><td>Relative Standard Uncertainty</td></tr></table>

Author contributions

Alexandre Quemet: conceptualization, writing – original draft (Introduction, Theory, Optimization of the {sample–spike} mixture, Spike monitoring, and Conclusion parts) and review, supervision. Amélie Hubert: conceptualization, writing – original draft (Nuclear forensics part). Alkiviadis Gourgiotis: conceptualization, writing – original draft (Environmental applications: natural radionuclides: U-series disequilibrium part). Ana María Sánchez Hernández: writing – original draft (Weighing procedure and Reference material parts) and review. Marielle Crozet: writing – original draft (Isotope dilution uncertainty part) and review. Guillaume Bailly: writing – original draft (Process control part). Andrew Dobney: writing – original draft (Irradiated samples part) and review. Georges Duhamel: writing – original draft (Safeguards part). Joe Hiess: writing – original draft (Safeguards part) and review. Urska Repinc: writing – original draft (Safeguards part) and review. Sébastien Mialle: writing – original draft (Isotopic homogenization of the sample–spike mixture and Irradiated samples part). Béatrice Boulet: writing – original draft (Application to environmental monitoring of nuclear facilities part). Raphaelle Escoube: writing – original draft (Biological applications part). Céline Bouvier-Capely: writing – original draft (Biological applications part). Fabien Pointurier: writing – review & editing. Sébastien Picart: writing – original draft (Weighing uncertainty and Interlaboratory comparison involving ID-MS parts) and review, supervision.

Conflicts of interest

There are no conflicts to declare.

References

1 M. L. D. P. Godoy, J. M. Godoy, L. A. Roldão and L. Tauhata, Determination of total content and isotopic compositions of plutonium and uranium in environmental samples for safeguards purposes by ICP-QMS, *J. Environ. Radioact.*, 2009, **100**, 613–625.

2 S. Boulyga, S. Konegger-Kappel, S. Richter and L. Sangély, Mass spectrometric analysis for nuclear safeguards, *J. Anal. At. Spectrom.*, 2015, **30**(7), 1469–1489.

3 A. Quemet, E. Buravand, B. Catanese, P. Huot, V. Dalier and A. Ruas, Monitoring the plutonium depletion in dissolution residues of a spent fuel solution using a surrogate and

<figure><img src="image_33.png" /></figure>
ID-MS has the potential to satisfy current and future needs in radioanalytical chemistry.

List of acronyms

<table><tr><td>CAB</td><td>Cellulose Acetate Butyrate</td></tr><tr><td>CCQM</td><td>Consultative Committee for Amount of Substance</td></tr><tr><td>CEA</td><td>French Alternative Energy and Atomic Energy Commission</td></tr><tr><td>CETAMA</td><td>Commission for the Establishment of Analytical Methods</td></tr><tr><td>CMC</td><td>CarboxyMethyl Cellulose sodium salt</td></tr><tr><td>CRM</td><td>Certified Reference Material</td></tr><tr><td>F</td><td>Error Multiplication Factor</td></tr><tr><td>HEU</td><td>Highly Enriched Uranium</td></tr><tr><td>HKED</td><td>Hybrid K-Edge Densitometry</td></tr><tr><td>HRGS</td><td>High Resolution Gamma Spectrometry</td></tr><tr><td>HR-ICP-MS</td><td>High Resolution-Inductively Coupled Plasma Mass Spectrometry</td></tr><tr><td>HU-1</td><td>Harwell Uraninite</td></tr><tr><td>IAEA</td><td>International Atomic Energy Agency</td></tr><tr><td>IBDA</td><td>Isobaric Dilution Analysis</td></tr><tr><td>ICP-MS</td><td>Inductively Coupled Plasma Mass Spectrometry</td></tr><tr><td>ID</td><td>Isotope Dilution</td></tr><tr><td>ID-MS</td><td>Isotope Dilution Mass Spectrometry</td></tr><tr><td>ILCs</td><td>Inter-Laboratory Comparisons</td></tr><tr><td>IRSN</td><td>French Institute for Radiation Protection and Nuclear Safety</td></tr><tr><td>ITVs</td><td>International Target Values</td></tr><tr><td>JAEA</td><td>Japan Atomic Energy Agency</td></tr><tr><td>JRC</td><td>Joint Research Centre</td></tr><tr><td>LAAT</td><td>Atalante Analysis Laboratory</td></tr><tr><td>LEU</td><td>Low Enriched Uranium</td></tr><tr><td>LOD</td><td>Limit Of Detection</td></tr><tr><td>LSD</td><td>Large-Sized Dried</td></tr><tr><td>MC-ICP-MS</td><td>Multi-Collector-Inductively Coupled Plasma Mass Spectrometry</td></tr><tr><td>MCM</td><td>Monte Carlo Method</td></tr><tr><td>MOX</td><td>Mixed OXide</td></tr><tr><td>MPE</td><td>Maximum Permissible Deviation</td></tr><tr><td>MSSP</td><td>Member States Support Programme</td></tr><tr><td>MGA</td><td>Multi-Group Analysis</td></tr><tr><td>NBL</td><td>New Brunswick Laboratory</td></tr><tr><td>NFC</td><td>Nuclear Fuel Cycle</td></tr><tr><td>NIST</td><td>National Institute of Standards and Technology</td></tr><tr><td>NMRoRo</td><td>Nuclear Material Round Robin</td></tr><tr><td>NORM</td><td>Naturally Occurring Radioactive Material</td></tr><tr><td>NPL</td><td>National Physical Laboratory</td></tr><tr><td>NPP</td><td>Nuclear Power Plant</td></tr><tr><td>NWAL</td><td>IAEA Network Analytical Laboratories</td></tr><tr><td>OSL</td><td>On-Site Laboratory</td></tr><tr><td>PT</td><td>Proficiency Test</td></tr><tr><td>R</td><td>Isotope Ratio</td></tr><tr><td>SCK</td><td>Belgian Nuclear Research Centre</td></tr><tr><td>SGAS</td><td>Office of Safeguards Analytical Services</td></tr><tr><td>SGAS-ESL</td><td>Environmental Sample Laboratory of SGAS</td></tr></table>

<table><tr><td>SGAS</td><td>Nuclear Material Laboratory of SGAS</td></tr><tr><td>NML</td><td></td></tr><tr><td>SI</td><td>International System of Units</td></tr><tr><td>SRM</td><td>Standard Reference Material</td></tr><tr><td>t<sub>1/2</sub></td><td>Half-life</td></tr><tr><td>TIMS</td><td>Thermal Ionization Mass Spectrometry</td></tr><tr><td>u</td><td>Standard Uncertainty</td></tr><tr><td>UOX</td><td>Uranium Oxide</td></tr><tr><td>u<sub>r</sub></td><td>Relative Standard Uncertainty</td></tr></table>

Author contributions

Alexandre Quemet: conceptualization, writing – original draft (Introduction, Theory, Optimization of the {sample–spike} mixture, Spike monitoring, and Conclusion parts) and review, supervision. Amélie Hubert: conceptualization, writing – original draft (Nuclear forensics part). Alkiviadis Gourgiotis: conceptualization, writing – original draft (Environmental applications: natural radionuclides: U-series disequilibrium part). Ana María Sánchez Hernández: writing – original draft (Weighing procedure and Reference material parts) and review. Marielle Crozet: writing – original draft (Isotope dilution uncertainty part) and review. Guillaume Bailly: writing – original draft (Process control part). Andrew Dobney: writing – original draft (Irradiated samples part) and review. Georges Duhamel: writing – original draft (Safeguards part). Joe Hiess: writing – original draft (Safeguards part) and review. Urska Repinc: writing – original draft (Safeguards part) and review. Sébastien Mialle: writing – original draft (Isotopic homogenization of the sample–spike mixture and Irradiated samples part). Béatrice Boulet: writing – original draft (Application to environmental monitoring of nuclear facilities part). Raphaelle Escoube: writing – original draft (Biological applications part). Céline Bouvier-Capely: writing – original draft (Biological applications part). Fabien Pointurier: writing – review & editing. Sébastien Picart: writing – original draft (Weighing uncertainty and Interlaboratory comparison involving ID-MS parts) and review, supervision.

Conflicts of interest

There are no conflicts to declare.

References

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<figure><img src="image_33.png" /></figure>
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24 International Atomic Energy Agency, *International Target Values 2010 for Measurement Uncertainties in Safeguarding Nuclear Materials - STR368*, Vienna, Austria, 2010.

25 International Atomic Energy Agency, *International Target Values for Measurement Uncertainties in Safeguarding Nuclear Materials - STR368 (Revision1.1)*, Vienna, Austria, 2022.

26 J. Irrgeher, J. Vogl, J. Santner and T. Prohaska, *Sector Field Mass Spectrometry for Elemental and Isotopic Analysis*, ed. T Prohaska, J. Irrgeher, A. Zitek and N. Jakubowski, Royal Society of Chemistry, Cambridge, 2014. pp. 126–151, New Developments in Mass Spectrometry, Available from: DOI: **10.1039/9781849735407**.

27 G. Cavazzini, D. Roccato and A. Fasson, The determination of the isotopic composition of strontium, *Int. J. Mass Spectrom.*, 2022, **471**, 116757, DOI: **10.1016/j.ijms.2021.116757**.

28 L. Zhu, C. Xu, X. Hou, J. Qiao, Y. Zhao and G. Liu, Determination of Ultratrace Level 135 Cs and 135 Cs/137 Cs Ratio in Small Volume Seawater by Chemical Separation and Thermal Ionization Mass Spectrometry, *Anal. Chem.*, 2020, **92**, 6709–6718, DOI: **10.1021/acs.analchem.0c00688**.

29 A. Magre, B. Boulet, H. Isnard, S. Mialle, O. Evrard and L. Pourcelot, Innovative ICP-MS/MS Method To Determine the 135 Cs/137 Cs Ratio in Low Activity Environmental Samples, *Anal. Chem.*, 2023, **95**(17), 6923–6930, DOI: **10.1021/acs.analchem.3c00207**.

30 Y. Shibahara, S. Nakamura, A. Uehara, T. Fujii, S. Fukutani, A. Kimura, et al., Measurement of cesium isotopic ratio by thermal ionization mass spectrometry for neutron capture reaction studies on 135Cs, *J. Radioanal. Nucl. Chem.*, 2020, **325**(1), 155–165, DOI: **10.1007/s10967-020-07198-2**.

31 A. Quemet, M. Angenieux and A. Ruas, Nd, Am and Cm isotopic measurements after simultaneous separation in transmutation irradiated samples, *J. Anal. At. Spectrom.*, 2021, **36**(8), 1758–1767. Available from: http://xlink.rsc.org/?DOI=D1JA00165E.
plutonium isotope ratio measurements, *J. Radioanal. Nucl. Chem.*, 2020, **326**(1), 255–260, DOI: **10.1007/s10967-020-07311-5**.

4 BIPM, *International vocabulary of metrology – Basic and general concepts and associated terms (VIM)*, 3rd edn, 2008, vol. 3, Available from: http://www.bipm.org/utilsmemcommon/documents/jcgm/JCGM_200_2008.pdf.

5 M. Désenfant and M. Priel, Road map for measurement uncertainty evaluation, *Measurement*, 2006, **39**(9), 841–848. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0263224106000789.

6 *ISO 5725-1:2023, Accuracy (Trueness and Precision) of Measurement Methods and Results — Part 1: General Principles and Definitions*.

7 A. Quemet, A. Ruas, V. Dalier and C. Rivier, Americium isotope analysis by Thermal Ionization Mass Spectrometry using the Total Evaporation Method, *Int. J. Mass Spectrom.*, 2018, **431**, 8–14.

8 A. M. Gaffney, A. Hubert, W. S. Kinman, M. Magara, A. Okubo, F. Pointurier, et al., Round-robin 230Th-234U age dating of bulk uranium for nuclear forensics, *J. Radioanal. Nucl. Chem.*, 2016, **307**(3), 2055–2056, DOI: **10.1007/s10967-015-4334-8**.

9 F. Pointurier, A. Hubert and G. Roger, A method for dating small amounts of uranium, *J. Radioanal. Nucl. Chem.*, 2013, **296**(2), 593–598, DOI: **10.1007/s10967-012-2198-8**.

10 Z. Varga, K. Mayer, C. E. Bonamici, A. Hubert, I. Hutcheon, W. Kinman, et al., Validation of reference materials for uranium radiochronometry in the frame of nuclear forensic investigations, *Appl. Radiat. Isot.*, 2015, **102**, 81–86, DOI: **10.1016/j.apradiso.2015.05.005**.

11 P. van Calsteren and L. Thomas, Uranium-series dating applications in natural environmental science, *Earth Sci. Rev.*, 2006, **75**(1-4), 155–175. https://linkinghub.elsevier.com/retrieve/pii/S0012825205001418.

12 X. Hou and P. Roos, Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples, *Anal. Chim. Acta*, 2008, **608**(2), 105–139.

13 P. P. Povinec, Ultra-sensitive radionuclide analyses: new frontiers in radioanalytics, *J. Radioanal. Nucl. Chem.*, 2019, **322**(3), 1247–1255, DOI: **10.1007/s10967-019-06707-2**.

14 S. Diez-Fernández, H. Isnard, A. Nonell, C. Bresson and F. Chartier, Radionuclide analysis using collision-reaction cell ICP-MS technology: a review, *J. Anal. At. Spectrom.*, 2020, **35**(12), 2793–2819. Available from: http://xlink.rsc.org/?DOI=D0JA00211A.

15 T. R. E. Southwood and P. A. Henderson, *Ecological Methods*, Blackwell, 2015.

16 E. Roth, Critical evaluation of the use and analysis of stable isotopes (Technical Report), *Pure Appl. Chem.*, 1997, **69**(8), 1754–1813.

17 G. V. Hevesy and F. Paneth, Die Löslichkeit des Bleisulfids und Bleichromats, *Zeitschrift für Anorg Chemie.*, 1913, **82**(1), 323–328.

18 P. Goris, W. E. Duffy and F. H. Tingey, Uranium Determination by the Isotope Dilution Technique, *Anal. Chem.*, 1957, **29**(11), 1590–1592.

19 G. R. Tilton, L. T. Aldrich and M. G. Inghram, Mass Spectrometric Determination of Thorium, *Anal. Chem.*, 1954, **26**(5), 894–898, DOI: **10.1080/18811248.1967.9732709**.

20 J. Vogl, Characterisation of reference materials by isotope dilution mass spectrometry, *J. Anal. At. Spectrom.*, 2007, **22**(5), 475–492.

21 M. J. T. Milton and T. J. Quinn, Primary methods for the measurement of amount of substance, *Metrologia*, 2001, **38**(4), 289–296.

22 BIPM, *Consultative Committee for Amount of Substance (CCQM) — 5th Meeting (February 1999)*, 1999.

23 M. Crozet, D. Roudil, C. Rigaux, C. Bertorello, S. Picart and C. Maillard, EQRAIN: uranium and plutonium interlaboratory exercises from 1997 to 2016—comparison to ITVs-2010, *J. Radioanal. Nucl. Chem.*, 2019, **319**(3), 1013–1021, DOI: **10.1007/s10967-018-6399-7**.

24 International Atomic Energy Agency, *International Target Values 2010 for Measurement Uncertainties in Safeguarding Nuclear Materials - STR368*, Vienna, Austria, 2010.

25 International Atomic Energy Agency, *International Target Values for Measurement Uncertainties in Safeguarding Nuclear Materials - STR368 (Revision1.1)*, Vienna, Austria, 2022.

26 J. Irrgeher, J. Vogl, J. Santner and T. Prohaska, *Sector Field Mass Spectrometry for Elemental and Isotopic Analysis*, ed. T Prohaska, J. Irrgeher, A. Zitek and N. Jakubowski, Royal Society of Chemistry, Cambridge, 2014. pp. 126–151, New Developments in Mass Spectrometry, Available from: DOI: **10.1039/9781849735407**.

27 G. Cavazzini, D. Roccato and A. Fasson, The determination of the isotopic composition of strontium, *Int. J. Mass Spectrom.*, 2022, **471**, 116757, DOI: **10.1016/j.ijms.2021.116757**.

28 L. Zhu, C. Xu, X. Hou, J. Qiao, Y. Zhao and G. Liu, Determination of Ultratrace Level 135 Cs and 135 Cs/137 Cs Ratio in Small Volume Seawater by Chemical Separation and Thermal Ionization Mass Spectrometry, *Anal. Chem.*, 2020, **92**, 6709–6718, DOI: **10.1021/acs.analchem.0c00688**.

29 A. Magre, B. Boulet, H. Isnard, S. Mialle, O. Evrard and L. Pourcelot, Innovative ICP-MS/MS Method To Determine the 135 Cs/137 Cs Ratio in Low Activity Environmental Samples, *Anal. Chem.*, 2023, **95**(17), 6923–6930, DOI: **10.1021/acs.analchem.3c00207**.

30 Y. Shibahara, S. Nakamura, A. Uehara, T. Fujii, S. Fukutani, A. Kimura, et al., Measurement of cesium isotopic ratio by thermal ionization mass spectrometry for neutron capture reaction studies on 135Cs, *J. Radioanal. Nucl. Chem.*, 2020, **325**(1), 155–165, DOI: **10.1007/s10967-020-07198-2**.

31 A. Quemet, M. Angenieux and A. Ruas, Nd, Am and Cm isotopic measurements after simultaneous separation in transmutation irradiated samples, *J. Anal. At. Spectrom.*, 2021, **36**(8), 1758–1767. Available from: http://xlink.rsc.org/?DOI=D1JA00165E.

<figure><img src="image_34.png" /></figure>
<figure><img src="image_34.png" /></figure>

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<figure><img src="image_35.png" /></figure>

32 N. N. Wanna, K. Van Hoecke, A. Dobney, M. Vasile, T. Cardinales, and F. Vanhaecke, Determination of the lanthanides, uranium and plutonium by means of on-line high-pressure ion chromatography coupled with sector field inductively coupled plasma-mass spectrometry to characterize nuclear samples, *J. Chromatogr.* A, 2020, **1617**, 460839. Available from: https://linkinghub.elsevier.com/retrieve/pii/S002196731931310X.

33 N. N. Wanna, A. Dobney, K. Van Hoecke, M. Vasile and F. Vanhaecke, Quantification of uranium, plutonium, neodymium and gadolinium for the characterization of spent nuclear fuel using isotope dilution HPIC-SF-ICP-MS, *Talanta*, 2021, **221**(September 2020), 121592, DOI: **10.1016/j.talanta.2020.121592**.

34 L. Vio, G. Crétier, F. Chartier, V. Geertsen, A. Gourgiotis, H. Isnard, et al., Separation and analysis of lanthanides by isotachophoresis coupled with inductively coupled plasma mass spectrometry, *Talanta*, 2012, **99**, 586–593.

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42 P.-A. Chaboche, F. Pointurier, P. Sabatier, A. Foucher, T. Tiecher, J. P. G. Minella, et al., 240Pu/239Pu signatures allow refining the chronology of radionuclide fallout in South America, *Sci. Total Environ.*, 2022, **843**(April), 156943. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0048969722040402.

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44 A. M. Sánchez Hernández, J. Horta Domenech, D. Wojnowski and E. Zuleger, Improvement of the 241Pu/239Pu isotope ratio measurement by thermal ionisation mass spectrometry - An approach to account for the 241Am in-growth after plutonium purification, *Int. J. Mass Spectrom.*, 2021, **468**, 116660. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380621001408.

45 G. R. Eppich, Z. Mácsik, R. Katona, S. Konegger-Kappel, G. Stadelmann, A. Köpf, et al., Plutonium assay and isotopic composition measurements in nuclear safeguards samples by inductively coupled plasma mass spectrometry, *J. Anal. At. Spectrom.*, 2019, **34**(6), 1154–1165. Available from: http://xlink.rsc.org/?DOI=C9JA00047J.

46 A. Gourgiotis, H. Isnard, M. Aubert, E. Dupont, I. AlMahamid, G. Tiang, et al., Accurate determination of Curium and Californium isotopic ratios by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) in 248Cm samples for transmutation studies, *Int. J. Mass Spectrom.*, 2010, **291**(3), 101–107, DOI: **10.1016/j.ijms.2010.02.002**.

47 P. Rodríguez-González, J. M. Marchante-Gayón, J. I. García Alonso and A. Sanz-Medel, Isotope dilution analysis for elemental speciation: A tutorial review, *Spectrochim. Acta Part B At. Spectrosc.*, 2005, **60**(2), 151–207.

48 P. Rodríguez-González and J. I. García Alonso, Recent advances in isotope dilution analysis for elemental speciation, *J. Anal. At. Spectrom.*, 2010, **25**(3), 239–259.

49 J. Villanueva, M. Carrascal and J. Abian, Isotope dilution mass spectrometry for absolute quantification in proteomics: Concepts and strategies, *J. Proteomics*, 2014, **96**, 184–199, DOI: **10.1016/j.jprot.2013.11.004**.

50 C. Pin and B. Le Fèvre, Isotope Dilution with Matrix Element Removal: A Key for High-Precision, High-Accuracy Trace Analysis of Geological Samples Using Inductively Coupled Plasma-Mass Spectrometry, *Geostand. Geoanal. Res.*, 2002, **26**(2), 135–148, DOI: **10.1111/j.1751-908X.2002.tb00882.x**.

51 J. D. Fassett and P. J. Paulsen, Isotope Dilution Mass Spectrometry for Accurate Elemental Analysis, *Anal. Chem.*, 1989, **61**(10), 643A–649A.

52 F. Vanhaecke and P. Degryse, *Isotopic Analysis*, ed. F. Vanhaecke and P. Degryse, Wiley, 2012, Available from: DOI: **10.1002/9783527650484**.

53 P. J. De Bièvre and G. H. Debus, Precision mass spectrometric isotope dilution analysis, *Nucl. Instrum. Methods*, 1965, **32**(2), 224–228. Available from: https://linkinghub.elsevier.com/retrieve/pii/0029554X65905161.

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55 D. Roudil, C. Rigaux, C. Rivier, J. C. Hubinois and L. Aufore, CETAMA Contribution to Safeguards and Nuclear Forensic Analysis based on Nuclear Reference Materials, Procedia Chem., 2012, 7, 709–715, DOI: 10.1016/j.proche.2012.10.108.

56 R. Jakopič, A. Fankhauser, Y. Aregbe, S. Richter, M. Crozet, C. Maillard, et al., 243Am certified reference material for mass spectrometry, *J. Radioanal. Nucl. Chem.*, 2021, 327(1), 495–504, DOI: 10.1007/s10967-020-07521-x.

57 G. Canciani, Y. Davrain, M. Crozet, D. Roudil and S. Picart, Controlled Potential Coulometry for the accurate determination of plutonium in the presence of uranium: The role of sulfate complexation, *Talanta*, 2021, **222**, 121490, DOI: 10.1016/j.talanta.2020.121490.

58 C. Maillard, D. Maloubier, O. Boulay, V. Savigny and A. Quemet, U and Pu separation with U/TEVA resin : Influence of some parameters on chromatographic cycle performances, *J. Radioanal. Nucl. Chem.*, 2021, (0123456789, DOI: 10.1007/s10967-021-07986-4.

59 A. Quemet and S. Baghdadi, Optimization of double isotope dilution, *J. Anal. At. Spectrom.*, 2022, **37**(2), 240–248. Available from: http://pubs.rsc.org/en/Content/ArticleLanding/2022/JA/D1JA00322D.

60 IUPAC. The IUPAC Compendium of Chemical Terminology, *The IUPAC Compendium of Chemical Terminology*, ed. V. Gold, NC: International Union of Pure and Applied Chemistry (IUPAC), Research Triangle Park, 2019, p. 1670. Available from: https://goldbook.iupac.org/terms/view/L03540.

61 L. L. Yu, J. D. Fassett and W. F. Guthrie, Detection Limit of Isotope Dilution Mass Spectrometry, *Anal. Chem.*, 2002, **74**(15), 3887–3891, DOI: 10.1021/ac011254l.

62 L. Yang, Accurate and precise determination of isotopic ratios by MC-ICP-MS: A review, *Mass Spectrom. Rev.*, 2009, **28**(6), 990–1011. Available from: https://apps.who.int/iris/bitstream/handle/10665/254610/WHO-MSD-MER-2017.2-eng.pdf?sequence=1%0Ahttp://apps.who.int/iris/bitstream/handle/10665/254610/WHO-MSD-MER-2017.2-eng.pdf;jsessionid=F9A3B620D10ECFAF8498AC0E08EFCBC8?sequence=1%0Ahttp://apps.who.int/.

63 M. E. Wieser, D. Buhl, C. Bouman and J. Schwieters, High precision calcium isotope ratio measurements using a magnetic sector multiple collector inductively coupled plasma mass spectrometer, *J. Anal. At. Spectrom.*, 2004, **19**(7), 844. Available from: http://xlink.rsc.org/?DOI=b403339f.

64 L. Yang and R. E. Sturgeon, Comparison of mass bias correction models for the examination of isotopic composition of mercury using sector field ICP-MS, *J. Anal. At. Spectrom.*, 2003, **18**(12), 1452. Available from: http://xlink.rsc.org/?DOI=b307973b.

65 P. Lindahl, G. Olszewski and M. Eriksson, Performance and optimisation of triple quadrupole ICP-MS for accurate measurement of uranium isotopic ratios, *J. Anal. At. Spectrom.*, 2021, 14–16.

66 S. K. Aggarwal, Thermal ionisation mass spectrometry (TIMS) in nuclear science and technology – a review, *Anal. Methods*, 2016, **8**(1996), 942–957.

67 T. Prohaska, J. Irrgeher, A. Zitek and N. Jakubowski, Sector Field Mass Spectrometry for Elemental and Isotopic Analysis, *New Developments in Mass Spectrometry*, ed. T. Prohaska, J. Irrgeher, A. Zitek and N. Jakubowski, The Royal Society of Chemistry, 2014. Available from: https://books.rsc.org/books/book/996/Sector-Field-Mass-Spectrometry-for-Elemental-and.

68 F. Albarède, P. Telouk, J. Blichert-Toft, M. Boyet, A. Agranier and B. Nelson, Precise and accurate isotopic measurements using multiple-collector ICPMS, *Geochim. Cosmochim. Acta*, 2004, **68**(12), 2725–2744. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0016703703008871.

69 C. E. Mathew, V. K. Rai, C. Ottenfeld and R. Keller, Effect of weighing uncertainty on assay values by isotope dilution mass spectrometry, *J. Radioanal. Nucl. Chem.*, 2021, **328**(1), 235–243, DOI: 10.1007/s10967-021-07646-7.

70 ASTM C1380-04 - Standard Test Method for Determination of Uranium Content and Isotopic Composition by Isotope Dilution Mass Spectrometry.

71 P. van Belle, E. Zuleger and L. Duinslaeger, An improved self-checking weighing practice and a method for contamination detection for use in IDMS nuclear material assay, *INMM Rep*, 2008.

72 OIML, International Recommendation OIML R 111-1 Edition 2004 (E), *Int. Organ. Leg. Metrol.*, 2004, **2004**, 1–78. Available from: https://www.oiml.org/en/files/pdf_r/r111-1-e04.pdf.

73 K. Toth, R. Jakopic, J. Bauwens, C. Hennessy, F. Kehoe, U. Jakobsson, et al., Preparation and Certification of Large-Sized Dried (LSD) Spike: IRMM-1027w, JRC Ref. Mater. Rep., 2022, DOI: 10.2760/817757.

74 S. Belz, I. Bianchi, C. Cella, H. Emteborg, F. Fumagalli, O. Geiss, et al., *Current Status of the Quantification of Microplastics in Water - Results of a JRC/BAM Interlaboratory Comparison Study on PET in Water*, EUR 30799 EN, Publications Office of the European Union, 2021.

75 OIML R 33, 1979 *International Organization of Legal Metrology - Conventional Value of the Result of Weighing in Air*, 1979.

76 M. Ohata, T. Ichinose, N. Furuta, A. Shinohara and M. Chiba, Isotope Dilution Analysis of Se in Human Blood Serum by Using High-Power Nitrogen Microwave-Induced Plasma Mass Spectrometry Coupled with a Hydride Generation Technique, *Anal. Chem.*, 1998, **70**(13), 2726–2730.

77 R. Hoelzl, C. Hoelzl, L. Kotz and L. Fabry, The optimal amount of isotopic spike solution for ultratrace analysis by isotope dilution mass spectrometry, *Accredit. Qual. Assur.*, 1998, **3**(5), 185–188.

78 P. Bedson, Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS), Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS), Royal Society of Chemistry,
<figure><img src="image_36.png" /></figure>

55 D. Roudil, C. Rigaux, C. Rivier, J. C. Hubinois and L. Aufore, CETAMA Contribution to Safeguards and Nuclear Forensic Analysis based on Nuclear Reference Materials, Procedia Chem., 2012, 7, 709-715, DOI: 10.1016/j.proche.2012.10.108.

56 R. Jakopič, A. Fankhauser, Y. Aregbe, S. Richter, M. Crozet, C. Maillard, et al., 243Am certified reference material for mass spectrometry, *J. Radioanal. Nucl. Chem.*, 2021, 327(1), 495-504, DOI: 10.1007/s10967-020-07521-x.

57 G. Canciani, Y. Davrain, M. Crozet, D. Roudil and S. Picart, Controlled Potential Coulometry for the accurate determination of plutonium in the presence of uranium: The role of sulfate complexation, *Talanta*, 2021, **222**, 121490, DOI: 10.1016/j.talanta.2020.121490.

58 C. Maillard, D. Maloubier, O. Boulay, V. Savigny and A. Quemet, U and Pu separation with U/TEVA resin : Influence of some parameters on chromatographic cycle performances, *J. Radioanal. Nucl. Chem.*, 2021, (0123456789, DOI: 10.1007/s10967-021-07986-4.

59 A. Quemet and S. Baghdadi, Optimization of double isotope dilution, *J. Anal. At. Spectrom.*, 2022, **37**(2), 240-248. Available from: http://pubs.rsc.org/en/Content/ArticleLanding/2022/JA/D1JA00322D.

60 IUPAC. The IUPAC Compendium of Chemical Terminology, *The IUPAC Compendium of Chemical Terminology*, ed. V. Gold, NC: International Union of Pure and Applied Chemistry (IUPAC), Research Triangle Park, 2019, p. 1670. Available from: https://goldbook.iupac.org/terms/view/L03540.

61 L. L. Yu, J. D. Fassett and W. F. Guthrie, Detection Limit of Isotope Dilution Mass Spectrometry, *Anal. Chem.*, 2002, **74**(15), 3887-3891, DOI: 10.1021/ac011254l.

62 L. Yang, Accurate and precise determination of isotopic ratios by MC-ICP-MS: A review, *Mass Spectrom. Rev.*, 2009, **28**(6), 990-1011. Available from: https://apps.who.int/iris/bitstream/handle/10665/254610/WHO-MSD-MER-2017.2-eng.pdf?sequence=1%0Ahttp://apps.who.int/iris/bitstream/handle/10665/254610/WHO-MSD-MER-2017.2-eng.pdf;jsessionid=F9A3B620D10ECFAF8498AC0E08EFCBC8?sequence=1%0Ahttp://apps.who.int/.

63 M. E. Wieser, D. Buhl, C. Bouman and J. Schwieters, High precision calcium isotope ratio measurements using a magnetic sector multiple collector inductively coupled plasma mass spectrometer, *J. Anal. At. Spectrom.*, 2004, **19**(7), 844. Available from: http://xlink.rsc.org/?DOI=b403339f.

64 L. Yang and R. E. Sturgeon, Comparison of mass bias correction models for the examination of isotopic composition of mercury using sector field ICP-MS, *J. Anal. At. Spectrom.*, 2003, **18**(12), 1452. Available from: http://xlink.rsc.org/?DOI=b307973b.

65 P. Lindahl, G. Olszewski and M. Eriksson, Performance and optimisation of triple quadrupole ICP-MS for accurate measurement of uranium isotopic ratios, *J. Anal. At. Spectrom.*, 2021, 14-16.

66 S. K. Aggarwal, Thermal ionisation mass spectrometry (TIMS) in nuclear science and technology - a review, *Anal. Methods*, 2016, **8**(1996), 942-957.

67 T. Prohaska, J. Irrgeher, A. Zitek and N. Jakubowski, Sector Field Mass Spectrometry for Elemental and Isotopic Analysis, *New Developments in Mass Spectrometry*, ed. T. Prohaska, J. Irrgeher, A. Zitek and N. Jakubowski, The Royal Society of Chemistry, 2014. Available from: https://books.rsc.org/books/book/996/Sector-Field-Mass-Spectrometry-for-Elemental-and.

68 F. Albarède, P. Telouk, J. Blichert-Toft, M. Boyet, A. Agranier and B. Nelson, Precise and accurate isotopic measurements using multiple-collector ICPMS, *Geochim. Cosmochim. Acta*, 2004, **68**(12), 2725-2744. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0016703703008871.

69 C. E. Mathew, V. K. Rai, C. Ottenfeld and R. Keller, Effect of weighing uncertainty on assay values by isotope dilution mass spectrometry, *J. Radioanal. Nucl. Chem.*, 2021, **328**(1), 235-243, DOI: 10.1007/s10967-021-07646-7.

70 ASTM C1380-04 - Standard Test Method for Determination of Uranium Content and Isotopic Composition by Isotope Dilution Mass Spectrometry.

71 P. van Belle, E. Zuleger and L. Duinslaeger, An improved self-checking weighing practice and a method for contamination detection for use in IDMS nuclear material assay, *INMM Rep*, 2008.

72 OIML, International Recommendation OIML R 111-1 Edition 2004 (E), *Int. Organ. Leg. Metrol.*, 2004, **2004**, 1-78. Available from: https://www.oiml.org/en/files/pdf_r/r111-1-e04.pdf.

73 K. Toth, R. Jakopic, J. Bauwens, C. Hennessy, F. Kehoe, U. Jakobsson, et al., Preparation and Certification of Large-Sized Dried (LSD) Spike: IRMM-1027w, JRC Ref. Mater. Rep., 2022, DOI: 10.2760/817757.

74 S. Belz, I. Bianchi, C. Cella, H. Emteborg, F. Fumagalli, O. Geiss, et al., *Current Status of the Quantification of Microplastics in Water - Results of a JRC/BAM Interlaboratory Comparison Study on PET in Water*, EUR 30799 EN, Publications Office of the European Union, 2021.

75 OIML R 33, 1979 *International Organization of Legal Metrology - Conventional Value of the Result of Weighing in Air*, 1979.

76 M. Ohata, T. Ichinose, N. Furuta, A. Shinohara and M. Chiba, Isotope Dilution Analysis of Se in Human Blood Serum by Using High-Power Nitrogen Microwave-Induced Plasma Mass Spectrometry Coupled with a Hydride Generation Technique, *Anal. Chem.*, 1998, **70**(13), 2726-2730.

77 R. Hoelzl, C. Hoelzl, L. Kotz and L. Fabry, The optimal amount of isotopic spike solution for ultratrace analysis by isotope dilution mass spectrometry, *Accredit. Qual. Assur.*, 1998, **3**(5), 185-188.

78 P. Bedson, Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS), Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS), Royal Society of Chemistry,
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79 B. N. Colby, A. E. Rosecrance and M. E. Colby, Measurement parameter selection for quantitative isotope dilution gas chromatography/mass spectrometry, *Anal. Chem.*, 1981, 53(12), 1907–1911.

80 C. J. Park and J. K. Suh, Determination of Trace Elements in Rice Flour by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry, *J. Anal. At. Spectrom.*, 1997, 12(5), 573–577. Available from: http://xlink.rsc.org/?DOI=a607393j.

81 J. W. Eaton, GNU Octave and reproducible research, *J. Process Control*, 2012, 22(8), 1433–1438, DOI: 10.1016/j.jprocont.2012.04.006.

82 J. W. Eaton, D. Bateman, S. Hauberg and R. Wehbring, {GNU Octave} version 8.3.0 manual: a high-level interactive language for numerical computations, 2023, Available from: https://www.gnu.org/software/octave/doc/v8.3.0/.

83 J. Irrgeher, J. Vogl, J. Santner and T. Prohaska, Chapter 8 Measurement Strategies, In *Sector Field Mass Spectrometry for Elemental and Isotopic Analysis*, The Royal Society of Chemistry, 2015, pp. 126–151.

84 R. Jakopič, K. Toth, J. Bauwens, R. Buják, C. Hennessy, F. Kehoe, et al., 30 years of IRMM-1027 reference materials for fissile material accountancy and control: development, production and characterisation, *J. Radioanal. Nucl. Chem.*, 2021, 330(1), 333–345, DOI: 10.1007/s10967-021-07927-1.

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79 B. N. Colby, A. E. Rosecrance and M. E. Colby, Measurement parameter selection for quantitative isotope dilution gas chromatography/mass spectrometry, *Anal. Chem.*, 1981, 53(12), 1907–1911.

80 C. J. Park and J. K. Suh, Determination of Trace Elements in Rice Flour by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry, *J. Anal. At. Spectrom.*, 1997, 12(5), 573–577. Available from: http://xlink.rsc.org/?DOI=a607393j.

81 J. W. Eaton, GNU Octave and reproducible research, *J. Process Control*, 2012, 22(8), 1433–1438, DOI: 10.1016/j.jprocont.2012.04.006.

82 J. W. Eaton, D. Bateman, S. Hauberg and R. Wehbring, {GNU Octave} version 8.3.0 manual: a high-level interactive language for numerical computations, 2023, Available from: https://www.gnu.org/software/octave/doc/v8.3.0/.

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84 R. Jakopič, K. Toth, J. Bauwens, R. Buják, C. Hennessy, F. Kehoe, et al., 30 years of IRMM-1027 reference materials for fissile material accountancy and control: development, production and characterisation, *J. Radioanal. Nucl. Chem.*, 2021, 330(1), 333–345, DOI: 10.1007/s10967-021-07927-1.

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103 A. Beaumais, A. Mangeret, D. Suhard, P. Blanchart, M. Neji, C. Cazala, et al., Combined U-Pb isotopic signatures of U mill tailings from France and Gabon: A new potential tracer to assess their fingerprint on the environment, *J. Hazard Mater.*, 2022, **430**(February), 128484. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0304389422002722.

104 A. Gourgiotis, A. Mangeret, G. Manhès, P. Blanchart, L. Stetten, G. Morin, et al., New Insights into Pb Isotope Fingerprinting of U-Mine Material Dissemination in the Environment: Pb Isotopes as a Memory Dissemination Tracer, *Environ. Sci. Technol.*, 2020, **54**(2), 797–806, DOI: **10.1021/acs.est.9b04828**.

105 M. Ivanovich and R. S. Harmon, Uranium-series disequilibrium: applications to earth, *Marine & Envirol. Sci.*, 1992, **2**, 910.

106 J. H. Chen and G. J. Wasserburg, Isotopic Determination of Uranium in Picomole and Subpicomole Quantities, *Anal. Chem.*, 1982, **54**(2), 350, DOI: **10.1021/ac00239a601**.

107 T. Yokoyama, A. Makishima and E. Nakamura, Evaluation of the coprecipitation of incompatible trace elements with fluoride during silicate rock dissolution by acid digestion, *Chem. Geol.*, 1999, **157**(3–4), 175–187. Available from: https://linkinghub.elsevier.com/retrieve/pii/S000925419800206X.

108 P. Lindahl, G. Olszewski and M. Eriksson, Total dissolution of environmental samples for the determination of uranium and thorium by ICP-MS and alpha-particle spectrometry, *Appl. Radiat. Isot.*, 2022, **181**(October 2021), 110103, DOI: **10.1016/j.apradiso.2022.110103**.

109 E. Douville, E. Sallé, N. Frank, M. Eisele, E. Pons-Branchu and S. Ayrault, Rapid and accurate U–Th dating of ancient carbonates using inductively coupled plasma–quadrupole mass spectrometry, *Chem. Geol.*, 2010, **272**(1–4), 1–11, DOI: **10.1016/j.chemgeo.2010.01.007**.

110 G. Yang, H. Tazoe and M. Yamada, Determination of 236 U in environmental samples by single extraction chromatography coupled to triple-quadrupole inductively coupled plasma-mass spectrometry, *Anal. Chim. Acta*, 2016, **944**, 44–50, DOI: **10.1016/j.aca.2016.09.033**.

111 O. Alhassanieh, A. Abdul-Hadi, M. Ghafar and A. Aba, Separation of Th, U, Pa, Ra and Ac from natural uranium and thorium series, *Appl. Radiat. Isot.*, 1999, **51**(5), 493–498. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804399000688.

112 C. Dalencourt, M. N. Chabane, J.-C. Tremblay-Cantin and D. Larivière, A rapid sequential chromatographic separation of U- and Th-decay series radionuclides in water samples, *Talanta*, 2020, **207**(May 2019), 120282, DOI: **10.1016/j.talanta.2019.120282**.

113 A. W. Knight, E. S. Eitrheim, A. W. Nelson, S. Nelson and M. K. Schultz, A simple-rapid method to separate uranium, thorium, and protactinium for U-series age-

dating of materials, *J. Environ. Radioact.*, 2014, **134**, 66–74, DOI: **10.1016/j.jenvrad.2014.02.010**.

114 G. Manhes, C. Allegre and A. Provost, U-Th-Pb systematics of the eucrite "Juvinas": Precise age determination and evidence for exotic lead, *Geochim. Cosmochim. Acta*, 1984, **48**(11), 2247–2264. Available from: https://linkinghub.elsevier.com/retrieve/pii/0016703784902217.

115 M. Verlinde, J. Gorny, G. Montavon, S. Khalfallah, B. Boulet, C. Augeray, et al., A new rapid protocol for 226Ra separation and preconcentration in natural water samples using molecular recognition technology for ICP-MS analysis, *J. Environ. Radioact.*, 2019, **202**(February), 1–7, DOI: **10.1016/j.jenvrad.2019.02.003**.

116 D. Larivière, V. N. Epov, R. D. Evans and R. J. Cornett, Determination of radium-226 in environmental samples by inductively coupled plasma mass spectrometry after sequential selective extraction, *J. Anal. At. Spectrom.*, 2003, **18**(4), 338–343. Available from: http://xlink.rsc.org/?DOI=b212361d.

117 D. Larivière, V. N. Epov, K. M. Reiber, R. J. Cornett and R. D. Evans, Micro-extraction procedures for the determination of Ra-226 in well waters by SF-ICP-MS, *Anal. Chim. Acta*, 2005, **528**(2), 175–182. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0003267004013030.

118 C. Dalencourt, A. Michaud, A. Habibi, A. Leblanc and D. Larivière, Rapid, versatile and sensitive method for the quantification of radium in environmental samples through cationic extraction and inductively coupled plasma mass spectrometry, *J. Anal. At. Spectrom.*, 2018, **33**(6), 1031–1040. Available from: http://xlink.rsc.org/?DOI=C8JA00060C.

119 B. Ghaleb, E. Pons-Branchu and P. Deschamps, Improved method for radium extraction from environmental samples and its analysis by thermal ionization mass spectrometry, *J. Anal. At. Spectrom.*, 2004, **19**(7), 906. Available from: http://xlink.rsc.org/?DOI=b402237h.

120 A. S. Cohen and R. K. O'Nions, Precise determination of femtogram quantities of radium by thermal ionization mass spectrometry, *Anal. Chem.*, 1991, **63**(23), 2705–2708, DOI: **10.1021/ac00023a008**.

121 F. Chabaux, D. B. Othman and J. L. Birck, A new Ra-Ba chromatographic separation and its application to Ra mass-spectrometric measurement in volcanic rocks, *Chem. Geol.*, 1994, **114**(3–4), 191–197. Available from: https://linkinghub.elsevier.com/retrieve/pii/0009254194900523.

122 A. P. Fleer and M. P. Bacon, In *Notes on Some Techniques of Marine Particle Analysis Used at Whoi*, 2013, pp. 223–226, Available from: DOI: **10.1029/GM063p0223**.

123 R. A. Mortlock, R. G. Fairbanks, T. Chiu and J. Rubenstein, 230Th/234U/238U and 231Pa/235U ages from a single fossil coral fragment by multi-collector magnetic-sector inductively coupled plasma mass spectrometry, *Geochim. Cosmochim. Acta*, 2005, **69**(3), 649–657. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0016703704005216.

<figure><img src="image_37.png" /></figure>
231Pa230Th fractionation in the Eurasian Basin, *Chem. Geol.*, 2020, 532(April 2019), 119380. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0009254119305091.

103 A. Beaumais, A. Mangeret, D. Suhard, P. Blanchart, M. Neji, C. Cazala, et al., Combined U-Pb isotopic signatures of U mill tailings from France and Gabon: A new potential tracer to assess their fingerprint on the environment, *J. Hazard Mater.*, 2022, **430**(February), 128484. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0304389422002722.

104 A. Gourgiotis, A. Mangeret, G. Manhès, P. Blanchart, L. Stetten, G. Morin, et al., New Insights into Pb Isotope Fingerprinting of U-Mine Material Dissemination in the Environment: Pb Isotopes as a Memory Dissemination Tracer, *Environ. Sci. Technol.*, 2020, **54**(2), 797–806, DOI: **10.1021/acs.est.9b04828**.

105 M. Ivanovich and R. S. Harmon, Uranium-series disequilibrium: applications to earth, *Marine & Envirol. Sci.*, 1992, **2**, 910.

106 J. H. Chen and G. J. Wasserburg, Isotopic Determination of Uranium in Picomole and Subpicomole Quantities, *Anal. Chem.*, 1982, **54**(2), 350, DOI: **10.1021/ac00239a601**.

107 T. Yokoyama, A. Makishima and E. Nakamura, Evaluation of the coprecipitation of incompatible trace elements with fluoride during silicate rock dissolution by acid digestion, *Chem. Geol.*, 1999, **157**(3–4), 175–187. Available from: https://linkinghub.elsevier.com/retrieve/pii/S000925419800206X.

108 P. Lindahl, G. Olszewski and M. Eriksson, Total dissolution of environmental samples for the determination of uranium and thorium by ICP-MS and alpha-particle spectrometry, *Appl. Radiat. Isot.*, 2022, **181**(October 2021), 110103, DOI: **10.1016/j.apradiso.2022.110103**.

109 E. Douville, E. Sallé, N. Frank, M. Eisele, E. Pons-Branchu and S. Ayrault, Rapid and accurate U–Th dating of ancient carbonates using inductively coupled plasma–quadrupole mass spectrometry, *Chem. Geol.*, 2010, 272(1–4), 1–11, DOI: **10.1016/j.chemgeo.2010.01.007**.

110 G. Yang, H. Tazoe and M. Yamada, Determination of 236 U in environmental samples by single extraction chromatography coupled to triple-quadrupole inductively coupled plasma-mass spectrometry, *Anal. Chim. Acta*, 2016, **944**, 44–50, DOI: **10.1016/j.aca.2016.09.033**.

111 O. Alhassanieh, A. Abdul-Hadi, M. Ghafar and A. Aba, Separation of Th, U, Pa, Ra and Ac from natural uranium and thorium series, *Appl. Radiat. Isot.*, 1999, **51**(5), 493–498. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804399000688.

112 C. Dalencourt, M. N. Chabane, J.-C. Tremblay-Cantin and D. Larivière, A rapid sequential chromatographic separation of U- and Th-decay series radionuclides in water samples, *Talanta*, 2020, **207**(May 2019), 120282, DOI: **10.1016/j.talanta.2019.120282**.

113 A. W. Knight, E. S. Eitrheim, A. W. Nelson, S. Nelson and M. K. Schultz, A simple-rapid method to separate uranium, thorium, and protactinium for U-series age-

dating of materials, *J. Environ. Radioact.*, 2014, **134**, 66–74, DOI: **10.1016/j.jenvrad.2014.02.010**.

114 G. Manhes, C. Allegre and A. Provost, U-Th-Pb systematics of the eucrite "Juvinas": Precise age determination and evidence for exotic lead, *Geochim. Cosmochim. Acta*, 1984, **48**(11), 2247–2264. Available from: https://linkinghub.elsevier.com/retrieve/pii/0016703784902217.

115 M. Verlinde, J. Gorny, G. Montavon, S. Khalfallah, B. Boulet, C. Augeray, et al., A new rapid protocol for 226Ra separation and preconcentration in natural water samples using molecular recognition technology for ICP-MS analysis, *J. Environ. Radioact.*, 2019, **202**(February), 1–7, DOI: **10.1016/j.jenvrad.2019.02.003**.

116 D. Larivière, V. N. Epov, R. D. Evans and R. J. Cornett, Determination of radium-226 in environmental samples by inductively coupled plasma mass spectrometry after sequential selective extraction, *J. Anal. At. Spectrom.*, 2003, **18**(4), 338–343. Available from: http://xlink.rsc.org/?DOI=b212361d.

117 D. Larivière, V. N. Epov, K. M. Reiber, R. J. Cornett and R. D. Evans, Micro-extraction procedures for the determination of Ra-226 in well waters by SF-ICP-MS, *Anal. Chim. Acta*, 2005, **528**(2), 175–182. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0003267004013030.

118 C. Dalencourt, A. Michaud, A. Habibi, A. Leblanc and D. Larivière, Rapid, versatile and sensitive method for the quantification of radium in environmental samples through cationic extraction and inductively coupled plasma mass spectrometry, *J. Anal. At. Spectrom.*, 2018, **33**(6), 1031–1040. Available from: http://xlink.rsc.org/?DOI=C8JA00060C.

119 B. Ghaleb, E. Pons-Branchu and P. Deschamps, Improved method for radium extraction from environmental samples and its analysis by thermal ionization mass spectrometry, *J. Anal. At. Spectrom.*, 2004, **19**(7), 906. Available from: http://xlink.rsc.org/?DOI=b402237h.

120 A. S. Cohen and R. K. O'Nions, Precise determination of femtogram quantities of radium by thermal ionization mass spectrometry, *Anal. Chem.*, 1991, **63**(23), 2705–2708, DOI: **10.1021/ac00023a008**.

121 F. Chabaux, D. B. Othman and J. L. Birck, A new Ra-Ba chromatographic separation and its application to Ra mass-spectrometric measurement in volcanic rocks, *Chem. Geol.*, 1994, **114**(3–4), 191–197. Available from: https://linkinghub.elsevier.com/retrieve/pii/0009254194900523.

122 A. P. Fleer and M. P. Bacon, In *Notes on Some Techniques of Marine Particle Analysis Used at Whoi*, 2013, pp. 223–226, Available from: DOI: **10.1029/GM063p0223**.

123 R. A. Mortlock, R. G. Fairbanks, T. Chiu and J. Rubenstone, 230Th/234U/238U and 231Pa/235U ages from a single fossil coral fragment by multi-collector magnetic-sector inductively coupled plasma mass spectrometry, *Geochim. Cosmochim. Acta*, 2005, **69**(3), 649–657. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0016703704005216.

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124 M. Levier, M. Roy-Barman, C. Colin and A. Dapoigny, Determination of low level of actinium 227 in seawater and freshwater by isotope dilution and mass spectrometry, *Mar. Chem.*, 2021, **233**(March), 103986, DOI: **10.1016/j.marchem.2021.103986**.

125 T. M. Kayzar and R. W. Williams, Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers, *J. Radioanal. Nucl. Chem.*, 2016, **307**(3), 2061–2068, DOI: **10.1007/s10967-015-4435-4**.

126 M. Boudias, A. Gourgiotis, G. Montavon, C. Cazala, V. Pichon and N. Delaunay, 226Ra and 137Cs determination by inductively coupled plasma mass spectrometry: state of the art and perspectives including sample pretreatment and separation steps, *J. Environ. Radioact.*, 2022, **244–245**, 106812. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0265931X22000029.

127 L. A. Dietz, C. F. Paghugki and G. A. Land, Internal Standard Technique for Precise Isotopic Abundance Measurments in Thermal Ionization Mass Spectrometry, *Anal. Chem.*, 1962, **34**(6), 709–710, DOI: **10.1021/ac60186a001**.

128 H. Cheng, R. Edwards, J. Hoff, C. Gallup, D. Richards and Y. Asmerom, The half-lives of uranium-234 and thorium-230, *Chem. Geol.*, 2000, **169**(1–2), 17–33. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0009254199001576.

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124 M. Levier, M. Roy-Barman, C. Colin and A. Dapoigny, Determination of low level of actinium 227 in seawater and freshwater by isotope dilution and mass spectrometry, *Mar. Chem.*, 2021, **233**(March), 103986, DOI: **10.1016/j.marchem.2021.103986**.

125 T. M. Kayzar and R. W. Williams, Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers, *J. Radioanal. Nucl. Chem.*, 2016, **307**(3), 2061–2068, DOI: **10.1007/s10967-015-4435-4**.

126 M. Boudias, A. Gourgiotis, G. Montavon, C. Cazala, V. Pichon and N. Delaunay, 226Ra and 137Cs determination by inductively coupled plasma mass spectrometry: state of the art and perspectives including sample pretreatment and separation steps, *J. Environ. Radioact.*, 2022, **244–245**, 106812. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0265931X22000029.

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140 NIST, *Standard Reference Material 4328C Thorium-229 Radioactivity Standard*, National Institute of Standards and Technology, Gaithersburg, 2013.

141 P. de Lavison, L. J. Husband, S. M. Jerome, J. D. Keightley, A. P. Woodman, D. H. Woods, et al., The standardisation of for an environmental yield tracer, *Appl. Radiat. Isot.*, 2000, **53**(1–2), 243–249. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804300001779.

142 K. W. W. Sims, J. B. Gill, A. Dosseto, D. L. Hoffmann, C. C. Lundstrom, R. W. Williams, et al., An Inter-Laboratory Assessment of the Thorium Isotopic Composition of Synthetic and Rock Reference Materials, *Geostand. Geoanal. Res.*, 2008, **32**(1), 65–91, DOI: **10.1111/j.1751-908X.2008.00870.x**.

143 A. Gourgiotis, J. L. Reyss, N. Frank, A. Guihou and C. Anagnostou, Uranium and radium diffusion in organic-rich sediments (sapropels), *Geochem., Geophys., Geosyst.*, 2011, **12**(9), 1–15, DOI: **10.1029/2011GC003646**.

144 M. Choi, R. Francois, K. Sims, M. Bacon, S. Brown-Leger, A. Fleer, et al., Rapid determination of 230Th and 231Pa in seawater by desolvated micro-nebulization Inductively Coupled Plasma magnetic sector mass spectrometry, *Mar. Chem.*, 2001, **76**(1–2), 99–112. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0304420301000500.

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146 LNHB, Atomic and nuclear data - Table of radionuclides, [cited 2023 Nov 14], Available from: http://www.lnhb.fr/nuclear-data/nuclear-data-table/.

147 D. Larivière, D. K. Brownell, V. N. Epov, R. J. Cornett and R. D. Evans, Determination of 226Ra in sediments by ICP-MS: A comparative study of three sample preparation approaches, *J. Radioanal. Nucl. Chem.*, 2007, **273**(2), 337–344, DOI: **10.1007/s10967-007-6870-3**.

148 A. M. Volpe, J. A. Olivares and M. T. Murrell, Determination of radium isotope ratios and abundances in geological samples by thermal ionization mass spectrometry, *Anal. Chem.*, 1991, **63**(9), 913–916, DOI: **10.1021/ac00009a015**.

149 Z. Varga, Ultratrace-level radium-226 determination in seawater samples by isotope dilution inductively coupled plasma mass spectrometry, *Anal. Bioanal. Chem.*, 2008, **390**(2), 511–519, DOI: **10.1007/s00216-007-1394-9**.

150 Y.-T. Hsieh and G. M. Henderson, Precise measurement of 228Ra/226Ra ratios and Ra concentrations in seawater samples by multi-collector ICP mass spectrometry, *J. Anal. At. Spectrom.*, 2011, **26**(7), 1338. Available from: http://xlink.rsc.org/?DOI=c1ja10013k.

151 L. I. Bradtmiller, J. F. McManus and L. F. Robinson, 231Pa/230Th evidence for a weakened but persistent Atlantic meridional overturning circulation during Heinrich Stadial 1, *Nat. Commun.*, 2014, 5(1), 5817. Available from: https://www.nature.com/articles/ncomms6817.

152 M. Levier, M. Roy-Barman, L. Foliot, A. Dapoigny and F. Lacan, Distribution of Pa in the Atlantic sector of the Southern Ocean: Tracking scavenging during water mass mixing along neutral density surfaces, *Deep-Sea Res. Part I Oceanogr. Res. Pap.*, 2023, **194**, 103951. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0967063722002643.

153 D. A. Pickett, M. T. Murrell and R. W. Williams, Determination of Femtogram Quantities of Protactinium in Geologic Samples by Thermal Ionization Mass Spectrometry, *Anal. Chem.*, 1994, **66**(7), 1044–1049, DOI: **10.1021/ac00079a020**.

154 M. Regelous, S. Turner, T. Elliott, K. Rostami and C. Hawkesworth, Measurement of Femtogram Quantities of Protactinium in Silicate Rock Samples by Multicollector Inductively Coupled Plasma Mass Spectrometry, *Anal. Chem.*, 2008, **80**(1), 344, DOI: **10.1021/ac702316r**.

155 V. P. Chechev and N. K. Kuzmenko, Decay Data Evaluation Project (DDEP): Evaluation of the main 233Pa decay characteristics, *Appl. Radiat. Isot.*, 2006, **64**(10–11), 1403–1411. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804306001072.

156 R. M. Essex, R. W. Williams, K. C. Treinen, R. Collé, R. Fitzgerald, R. Galea, et al., Preparation and calibration of a 231Pa reference material, *J. Radioanal. Nucl. Chem.*, 2019, **322**(3), 1593–1604, DOI: **10.1007/s10967-019-06711-6**.

157 M. Roy-Barman, L. Foliot, E. Douville, N. Leblond, F. Gazeau, M. Bressac, et al., Contrasted release of insoluble elements (Fe, Al, rare earth elements, Th, Pa) after dust deposition in seawater: a tank experiment

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158 C.-C. Shen, H. Cheng, R. L. Edwards, S. B. Moran, H. N. Edmonds, J. A. Hoff, et al., Measurement of Attogram Quantities of 231 Pa in Dissolved and Particulate Fractions of Seawater by Isotope Dilution Thermal Ionization Mass Spectroscopy, *Anal. Chem.*, 2003, **75**(5), 1075–1079, DOI: **10.1021/ac026247r**.

159 A. Beranoaguirre, C. Pin, M. E. Sanchez-Lorda, S. García de Madinabeitia and J. I. Gil Ibarguchi, An evaluation of Rb-Sr isotope dilution analyses with a 86Sr-enriched tracer and Multiple Collection-ICP-MS, *Int. J. Mass Spectrom.*, 2019, **435**, 234–240. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380618302574.

160 L. O. Nicolaysen, Graphic interpretation of discordant age measurements on metamorphic rocks, *Ann. N. Y. Acad. Sci.*, 1961, **91**(2), 198–206, DOI: **10.1111/j.1749-6632.1961.tb35452.x**.

161 C. Pin, S. Joannon, C. Bosq, B. Le Fèvre and P.-J. Gauthier, Precise determination of Rb, Sr, Ba, and Pb in geological materials by isotope dilution and ICP-quadrupole mass spectrometry following selective separation of the analytes, *J. Anal. At. Spectrom.*, 2003, **18**(2), 135–141. Available from: http://xlink.rsc.org/?DOI=b211832g.

162 ISO 17294-2:2023 "Water Quality - Application of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) - Part 2: Determination of Selected Elements Including Uranium Isotopes", 2023.

163 ISO 20899:2018 "Water Quality - Plutonium and Neptunium - Test Method Using ICP-MS", 2018.

164 ISO 18589-4:2019 "Measurement of Radioactivity in the Environment-Soil - Part 4: Plutonium 238 and Plutonium 239 + 240", 2019.

165 L. Pourcelot, O. Masson, L. Saey, S. Conil, B. Boulet and N. Cariou, Empirical calibration of uranium releases in the terrestrial environment of nuclear fuel cycle facilities, *J. Environ. Radioact.*, 2017, **171**, 74–82. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0265931X16305586.

166 Y. Shao, J. Zhang, M. Luo, D. Xu and L. Ma, A review of anthropogenic radionuclide 236U: Environmental application and analytical advances, *J. Environ. Radioact.*, 2022, 251–252:106944. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0265931X22001357.

167 J. M. Kelley, L. A. Bond and T. M. Beasley, Global distribution of Pu isotopes and 237Np, *Sci. Total Environ.*, 1999, **237–238**, 483–500. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0048969799001606.

168 United Nations Scientific Committee on the Effects of Atomic Radiation, *Sources and Effects of Ionizing Radiation Volume I: Source*, United Nations Scientific Committee on the Effects, 2000, vol. I, pp. 1–654.

169 E. Hrnecek, P. Steier and A. Wallner, Determination of plutonium in environmental samples by AMS and alpha spectrometry, *Appl. Radiat. Isot.*, 2005, **63**(5–6), 633–638.
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146 LNHB, Atomic and nuclear data - Table of radionuclides, [cited 2023 Nov 14], Available from: http://www.lnhb.fr/nuclear-data/nuclear-data-table/.

147 D. Larivière, D. K. Brownell, V. N. Epov, R. J. Cornett and R. D. Evans, Determination of 226Ra in sediments by ICP-MS: A comparative study of three sample preparation approaches, *J. Radioanal. Nucl. Chem.*, 2007, **273**(2), 337–344, DOI: **10.1007/s10967-007-6870-3**.

148 A. M. Volpe, J. A. Olivares and M. T. Murrell, Determination of radium isotope ratios and abundances in geological samples by thermal ionization mass spectrometry, *Anal. Chem.*, 1991, **63**(9), 913–916, DOI: **10.1021/ac00009a015**.

149 Z. Varga, Ultratrace-level radium-226 determination in seawater samples by isotope dilution inductively coupled plasma mass spectrometry, *Anal. Bioanal. Chem.*, 2008, **390**(2), 511–519, DOI: **10.1007/s00216-007-1394-9**.

150 Y.-T. Hsieh and G. M. Henderson, Precise measurement of 228Ra/226Ra ratios and Ra concentrations in seawater samples by multi-collector ICP mass spectrometry, *J. Anal. At. Spectrom.*, 2011, **26**(7), 1338. Available from: http://xlink.rsc.org/?DOI=c1ja10013k.

151 L. I. Bradtmiller, J. F. McManus and L. F. Robinson, 231Pa/230Th evidence for a weakened but persistent Atlantic meridional overturning circulation during Heinrich Stadial 1, *Nat. Commun.*, 2014, 5(1), 5817. Available from: https://www.nature.com/articles/ncomms6817.

152 M. Levier, M. Roy-Barman, L. Foliot, A. Dapoigny and F. Lacan, Distribution of Pa in the Atlantic sector of the Southern Ocean: Tracking scavenging during water mass mixing along neutral density surfaces, *Deep-Sea Res. Part I Oceanogr. Res. Pap.*, 2023, **194**, 103951. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0967063722002643.

153 D. A. Pickett, M. T. Murrell and R. W. Williams, Determination of Femtogram Quantities of Protactinium in Geologic Samples by Thermal Ionization Mass Spectrometry, *Anal. Chem.*, 1994, **66**(7), 1044–1049, DOI: **10.1021/ac00079a020**.

154 M. Regelous, S. Turner, T. Elliott, K. Rostami and C. Hawkesworth, Measurement of Femtogram Quantities of Protactinium in Silicate Rock Samples by Multicollector Inductively Coupled Plasma Mass Spectrometry, *Anal. Chem.*, 2008, **80**(1), 344, DOI: **10.1021/ac702316r**.

155 V. P. Chechev and N. K. Kuzmenko, Decay Data Evaluation Project (DDEP): Evaluation of the main 233Pa decay characteristics, *Appl. Radiat. Isot.*, 2006, **64**(10–11), 1403–1411. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804306001072.

156 R. M. Essex, R. W. Williams, K. C. Treinen, R. Collé, R. Fitzgerald, R. Galea, et al., Preparation and calibration of a 231Pa reference material, *J. Radioanal. Nucl. Chem.*, 2019, **322**(3), 1593–1604, DOI: **10.1007/s10967-019-06711-6**.

157 M. Roy-Barman, L. Foliot, E. Douville, N. Leblond, F. Gazeau, M. Bressac, et al., Contrasted release of insoluble elements (Fe, Al, rare earth elements, Th, Pa) after dust deposition in seawater: a tank experiment

approach, *Biogeosciences*, 2021, **18**(8), 2663–2678. Available from: https://bg.copernicus.org/articles/18/2663/2021/.

158 C.-C. Shen, H. Cheng, R. L. Edwards, S. B. Moran, H. N. Edmonds, J. A. Hoff, et al., Measurement of Attogram Quantities of 231 Pa in Dissolved and Particulate Fractions of Seawater by Isotope Dilution Thermal Ionization Mass Spectroscopy, *Anal. Chem.*, 2003, **75**(5), 1075–1079, DOI: **10.1021/ac026247r**.

159 A. Beranoaguirre, C. Pin, M. E. Sanchez-Lorda, S. García de Madinabeitia and J. I. Gil Ibarguchi, An evaluation of Rb-Sr isotope dilution analyses with a 86Sr-enriched tracer and Multiple Collection-ICP-MS, *Int. J. Mass Spectrom.*, 2019, **435**, 234–240. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380618302574.

160 L. O. Nicolaysen, Graphic interpretation of discordant age measurements on metamorphic rocks, *Ann. N. Y. Acad. Sci.*, 1961, **91**(2), 198–206, DOI: **10.1111/j.1749-6632.1961.tb35452.x**.

161 C. Pin, S. Joannon, C. Bosq, B. Le Fèvre and P.-J. Gauthier, Precise determination of Rb, Sr, Ba, and Pb in geological materials by isotope dilution and ICP-quadrupole mass spectrometry following selective separation of the analytes, *J. Anal. At. Spectrom.*, 2003, **18**(2), 135–141. Available from: http://xlink.rsc.org/?DOI=b211832g.

162 ISO 17294-2:2023 "Water Quality - Application of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) - Part 2: Determination of Selected Elements Including Uranium Isotopes", 2023.

163 ISO 20899:2018 "Water Quality - Plutonium and Neptunium - Test Method Using ICP-MS", 2018.

164 ISO 18589-4:2019 "Measurement of Radioactivity in the Environment-Soil - Part 4: Plutonium 238 and Plutonium 239 + 240", 2019.

165 L. Pourcelot, O. Masson, L. Saey, S. Conil, B. Boulet and N. Cariou, Empirical calibration of uranium releases in the terrestrial environment of nuclear fuel cycle facilities, *J. Environ. Radioact.*, 2017, **171**, 74–82. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0265931X16305586.

166 Y. Shao, J. Zhang, M. Luo, D. Xu and L. Ma, A review of anthropogenic radionuclide 236U: Environmental application and analytical advances, *J. Environ. Radioact.*, 2022, 251–252:106944. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0265931X22001357.

167 J. M. Kelley, L. A. Bond and T. M. Beasley, Global distribution of Pu isotopes and 237Np, *Sci. Total Environ.*, 1999, **237–238**, 483–500. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0048969799001606.

168 United Nations Scientific Committee on the Effects of Atomic Radiation, *Sources and Effects of Ionizing Radiation Volume I: Source*, United Nations Scientific Committee on the Effects, 2000, vol. I, pp. 1–654.

169 E. Hrnecek, P. Steier and A. Wallner, Determination of plutonium in environmental samples by AMS and alpha spectrometry, *Appl. Radiat. Isot.*, 2005, **63**(5–6), 633–638.
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170 H. Yamana, T. Yamamoto and H. Moriyama, Isotopic ratio of Pu released from fuel cycle facilities — importance of radiochemically pure 236Pu as a tracer, *Radioact. Environ.*, 2001, **1**, 31–46. Available from: https://linkinghub.elsevier.com/retrieve/pii/S156948600180005X.

171 R. Wellum, A. Verbruggen and R. Kessel, A new evaluation of the half-life of 241Pu, *J. Anal. At. Spectrom.*, 2009, **24**(6), 801. Available from: http://xlink.rsc.org/?DOI=b819584f.

172 P. Bouisset, M. Nohl, C. Cossonnet, B. Boulet, S. Thomas, N. Cariou, et al., Contribution of close-in fallout from the French atmospheric tests in inventories of 137Cs, 241Am and plutonium (238, 239, 240) in Gambier Islands (French Polynesia) - Signatures of stratospheric fallout in the Southern Hemisphere, *J. Environ. Radioact.*, 2021, **235-236**, 106624. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0265931X21000965.

173 V. P. Chechev, Standard Reference Data on the Nuclear Characteristics of the Alpha-Radiating Radionuclides 226Ra, 233U, 238Pu, and 239Pu, *Meas. Tech.*, 2001, **44**(11), 1134–1137.

174 H. Jaegler, F. Pointurier, Y. Onda, A. Hubert, J. P. Laceby, M. Cirella, et al., Plutonium isotopic signatures in soils and their variation (2011-2014) in sediment transiting a coastal river in the Fukushima Prefecture, Japan, *Environ. Pollut.*, 2018, **240**, 167–176. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0269749117347875.

175 K. Xiong, W. Bu, Y. Ni, X. Liu, J. Zheng, T. Aono, et al., Rapid monitoring of 241Am in small amount of sediment samples by combining extraction chromatography for highly efficient separation of interfering and matrix elements and ICP-MS/MS measurement, *Microchem. J.*, 2023, **190**, 108581. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0026265X23001996.

176 H. Zhang, X. Hou, J. Qiao and J. Lin, Determination of 241Am in Environmental Samples: A Review, *Molecules*, 2022, **27**(14), 4536. Available from: https://www.mdpi.com/1420-3049/27/14/4536.

177 B. Salbu and E. Holm. Radiochemical methods | Technetium, in *Encyclopedia of Analytical Science*, Elsevier, 2005, pp. 24–32. Available from: https://linkinghub.elsevier.com/retrieve/pii/B0123693977005197.

178 T. Hayakawa, H. Ko, M.-K. Cheoun, M. Kusakabe, T. Kajino, M. D. Usang, et al., Short-Lived Radioisotope 98Tc Synthesized by the Supernova Neutrino Process, *Phys. Rev. Lett.*, 2018, **121**(10), 102701, DOI: **10.1103/PhysRevLett.121.102701**.

179 L. Yang, W. Bu, K. Xiong, Y. Yang and T. Yang, Determination of 99Tc in solid environmental samples by combining alkali fusion and rapid separation using TRans Uranium elements resin in alkali medium to triple quadrupole inductively coupled plasma mass spectrometry, *Spectrochim. Acta Part B At. Spectrosc.*, 2022, **198**, 106564. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0584854722002087.

180 S. Pommé, J. Paepen and R. Van Ammel, Linearity check of an ionisation chamber through 99 mTc half-life measurements, *Appl. Radiat. Isot.*, 2018, **140**, 171–178. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804318302148.

181 E. García-Toraño, T. Altzitzoglou, P. Auerbach, M.-M. Bé, C. Bobin, P. Cassette, et al., The half-life of 129I, *Appl. Radiat. Isot.*, 2018, **140**, 157–162. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804318303348.

182 C. Carrier, H. Azza, A. Michelle, A. Celine, B. Didier, M. Denis, et al., Mass-shift mode to quantify low level 129 I in environmental samples by ICP-MS/MS, *J. Anal. At. Spectrom.*, 2022, 37(6), 1309–1317. Available from: http://xlink.rsc.org/?DOI=D2JA00128D.

183 J. Kim, J. Y. Kim, S. E. Bae, K. Song and J. H. Park, Review of the development in determination of 129I amount and the isotope ratio of 129I/127I using mass spectrometric measurements, *Microchem. J.*, 2021, **169**, 106476, DOI: **10.1016/j.microc.2021.106476**.

184 B. S. Matteson, S. K. Hanson, J. L. Miller and W. J. Oldham, Concurrent determination of 237Np and Pu isotopes using ICP-MS: Analysis of NIST environmental matrix standard reference materials 4357, 1646a, and 2702, *J. Environ. Radioact.*, 2015, **142**, 62–67, DOI: **10.1016/j.jenvrad.2015.01.007**.

185 S. Zhang, Z. Liu, G. Yang, J. Zheng, S. Pan, T. Aono, et al., Rapid Method To Determine 137Cs, 237Np, and Pu Isotopes in Seawater by SF-ICP-MS, *Anal. Chem.*, 2023, 95(46), 16892–16901.

186 S. J. Goldstein, A. A. Price, K. A. Hinrichs, S. P. Lamont, A. J. Nunn, R. S. Amato, et al., High-precision measurement of U-Pu-Np-Am concentrations and isotope ratios in environmental reference materials by mass spectrometry, *J. Environ. Radioact.*, 2021, 237(June), 106689, DOI: **10.1016/j.jenvrad.2021.106689**.

187 N. Qin, J. Zheng, G. Yang and K. Tagami, A comprehensive survey of reference materials for their use in quality assurance for the determination of Np-237 in environmental samples, *J. Environ. Radioact.*, 2024, 271(August 2023), 107328, DOI: **10.1016/j.jenvrad.2023.107328**.

188 K. Mayer, M. Wallenius and Z. Varga, Nuclear Forensic Science: Correlating Measurable Material Parameters to the History of Nuclear Material, *Chem. Rev.*, 2013, **113**(2), 884–900, DOI: **10.1021/cr300273f**.

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170 H. Yamana, T. Yamamoto and H. Moriyama, Isotopic ratio of Pu released from fuel cycle facilities — importance of radiochemically pure 236Pu as a tracer, *Radioact. Environ.*, 2001, **1**, 31–46. Available from: https://linkinghub.elsevier.com/retrieve/pii/S156948600180005X.

171 R. Wellum, A. Verbruggen and R. Kessel, A new evaluation of the half-life of 241Pu, *J. Anal. At. Spectrom.*, 2009, **24**(6), 801. Available from: http://xlink.rsc.org/?DOI=b819584f.

172 P. Bouisset, M. Nohl, C. Cossonnet, B. Boulet, S. Thomas, N. Cariou, et al., Contribution of close-in fallout from the French atmospheric tests in inventories of 137Cs, 241Am and plutonium (238, 239, 240) in Gambier Islands (French Polynesia) - Signatures of stratospheric fallout in the Southern Hemisphere, *J. Environ. Radioact.*, 2021, **235–236**, 106624. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0265931X21000965.

173 V. P. Chechev, Standard Reference Data on the Nuclear Characteristics of the Alpha-Radiating Radionuclides 226Ra, 233U, 238Pu, and 239Pu, *Meas. Tech.*, 2001, **44**(11), 1134–1137.

174 H. Jaegler, F. Pointurier, Y. Onda, A. Hubert, J. P. Laceby, M. Cirella, et al., Plutonium isotopic signatures in soils and their variation (2011-2014) in sediment transiting a coastal river in the Fukushima Prefecture, Japan, *Environ. Pollut.*, 2018, **240**, 167–176. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0269749117347875.

175 K. Xiong, W. Bu, Y. Ni, X. Liu, J. Zheng, T. Aono, et al., Rapid monitoring of 241Am in small amount of sediment samples by combining extraction chromatography for highly efficient separation of interfering and matrix elements and ICP-MS/MS measurement, *Microchem. J.*, 2023, **190**, 108581. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0026265X23001996.

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177 B. Salbu and E. Holm. Radiochemical methods | Technetium, in *Encyclopedia of Analytical Science*, Elsevier, 2005, pp. 24–32. Available from: https://linkinghub.elsevier.com/retrieve/pii/B0123693977005197.

178 T. Hayakawa, H. Ko, M.-K. Cheoun, M. Kusakabe, T. Kajino, M. D. Usang, et al., Short-Lived Radioisotope 98Tc Synthesized by the Supernova Neutrino Process, *Phys. Rev. Lett.*, 2018, **121**(10), 102701, DOI: **10.1103/PhysRevLett.121.102701**.

179 L. Yang, W. Bu, K. Xiong, Y. Yang and T. Yang, Determination of 99Tc in solid environmental samples by combining alkali fusion and rapid separation using TRans Uranium elements resin in alkali medium to triple quadrupole inductively coupled plasma mass spectrometry, *Spectrochim. Acta Part B At. Spectrosc.*, 2022, **198**, 106564. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0584854722002087.

180 S. Pommé, J. Paepen and R. Van Ammel, Linearity check of an ionisation chamber through 99 mTc half-life measurements, *Appl. Radiat. Isot.*, 2018, **140**, 171–178. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804318302148.

181 E. García-Toraño, T. Altzitzoglou, P. Auerbach, M.-M. Bé, C. Bobin, P. Cassette, et al., The half-life of 129I, *Appl. Radiat. Isot.*, 2018, **140**, 157–162. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804318303348.

182 C. Carrier, H. Azza, A. Michelle, A. Celine, B. Didier, M. Denis, et al., Mass-shift mode to quantify low level 129 I in environmental samples by ICP-MS/MS, *J. Anal. At. Spectrom.*, 2022, 37(6), 1309–1317. Available from: http://xlink.rsc.org/?DOI=D2JA00128D.

183 J. Kim, J. Y. Kim, S. E. Bae, K. Song and J. H. Park, Review of the development in determination of 129I amount and the isotope ratio of 129I/127I using mass spectrometric measurements, *Microchem. J.*, 2021, **169**, 106476, DOI: **10.1016/j.microc.2021.106476**.

184 B. S. Matteson, S. K. Hanson, J. L. Miller and W. J. Oldham, Concurrent determination of 237Np and Pu isotopes using ICP-MS: Analysis of NIST environmental matrix standard reference materials 4357, 1646a, and 2702, *J. Environ. Radioact.*, 2015, **142**, 62–67, DOI: **10.1016/j.jenvrad.2015.01.007**.

185 S. Zhang, Z. Liu, G. Yang, J. Zheng, S. Pan, T. Aono, et al., Rapid Method To Determine 137Cs, 237Np, and Pu Isotopes in Seawater by SF-ICP-MS, *Anal. Chem.*, 2023, 95(46), 16892–16901.

186 S. J. Goldstein, A. A. Price, K. A. Hinrichs, S. P. Lamont, A. J. Nunn, R. S. Amato, et al., High-precision measurement of U-Pu-Np-Am concentrations and isotope ratios in environmental reference materials by mass spectrometry, *J. Environ. Radioact.*, 2021, 237(June), 106689, DOI: **10.1016/j.jenvrad.2021.106689**.

187 N. Qin, J. Zheng, G. Yang and K. Tagami, A comprehensive survey of reference materials for their use in quality assurance for the determination of Np-237 in environmental samples, *J. Environ. Radioact.*, 2024, 271(August 2023), 107328, DOI: **10.1016/j.jenvrad.2023.107328**.

188 K. Mayer, M. Wallenius and Z. Varga, Nuclear Forensic Science: Correlating Measurable Material Parameters to the History of Nuclear Material, *Chem. Rev.*, 2013, **113**(2), 884–900, DOI: **10.1021/cr300273f**.

189 M. J. Kristo, A. M. Gaffney, N. Marks, K. Knight, W. S. Cassata and I. D. Hutcheon, Nuclear Forensic Science: Analysis of Nuclear Material Out of Regulatory Control, *Annu. Rev. Earth Planet Sci.*, 2016, **44**(1), 555–579. Available from: https://www.annualreviews.org/doi/10.1146/annurev-earth-060115-012309.

190 Z. Varga, M. Wallenius, M. Krachler, N. Rauff-Nisthar, L. Fongaro, A. Knott, et al., Trends and perspectives in Nuclear Forensic Science, *Trac. Trends Anal. Chem.*, 2022, **146**, 116503, DOI: **10.1016/j.trac.2021.116503**.

191 Z. Varga, C. Venchiarutti, A. Nicholl, J. Krajkó, R. Jakopič, K. Mayer, et al., IRMM-1000a and IRMM-1000b uranium
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192 C. Venchiarutti, Z. Varga, S. Richter, A. Nicholl, J. Krajko, R. Jakopič, et al., IRMM-1000a and IRMM-1000b: uranium reference materials certified for the production date based on the 230Th/234U radiochronometer. Part II: certification, *J. Radioanal. Nucl. Chem.*, 2016, **308**(1), 105–111, DOI: **10.1007/s10967-015-4368-y**.

193 S. J. Goldstein, M. T. Murrell and R. W. Williams, Half-life of 229Th, *Phys. Rev. C*, 1989, **40**(6), 2793–2795, DOI: **10.1103/PhysRevC.40.2793**.

194 H. Kikunaga, T. Suzuki, M. Nomura, T. Mitsugashira and A. Shinohara, Determination of the half-life of the ground state of 229Th by using 232U and 233U decay series, *Phys. Rev. C*, 2011, **84**(1), 014316, DOI: **10.1103/PhysRevC.84.014316**.

195 Z. Varga, A. Nicholl and K. Mayer, Determination of the 229Th half-life, *Phys. Rev. C*, 2014, **89**(6), 064310, DOI: **10.1103/PhysRevC.89.064310**.

196 R. M. Essex, J. L. Mann, R. Collé, L. Laureano-Perez, M. E. Bennett, H. Dion, et al., New determination of the 229Th half-life, *J. Radioanal. Nucl. Chem.*, 2018, **318**(1), 515–525.

197 G. R. Eppich, R. W. Williams, A. M. Gaffney and K. C. Schorzman, 235U-231Pa age dating of uranium materials for nuclear forensic investigations, *J. Anal. At. Spectrom.*, 2013, **28**(5), 666. Available from: http://xlink.rsc.org/?DOI=c3ja50041a.

198 K. C. Treinen, A. M. Gaffney, J. M. Rolison, K. M. Samperton, K. C. McHugh, M. L. Miller, et al., Improved protactinium spike calibration method applied to 231Pa-235U age-dating of certified reference materials for nuclear forensics, *J. Radioanal. Nucl. Chem.*, 2018, **318**(1), 209–219, DOI: **10.1007/s10967-018-6149-x**.

199 S. K. Aggarwal and D. Alamelu, A novel approach for the determination of 238Pu by thermal ionization mass spectrometry (TIMS) using interfering element correction methodology, *Int. J. Mass Spectrom.*, 2005, **241**(1), 83–88. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380604004300.

200 D. Alamelu, P. S. Khodade, P. M. Shah and S. K. Aggarwal, Investigations on atomic and oxide ion formation of plutonium and uranium in thermal ionization mass spectrometry (TIMS) for determination of 238Pu, *Int. J. Mass Spectrom.*, 2004, **239**(1), 51–56. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380604003756.

201 R. Jakopič, Y. Aregbe, S. Richter, E. Zuleger, S. Mialle, S. D. Balsley, et al., Verification measurements of the IRMM-1027 and the IAEA large-sized dried (LSD) spikes, *J. Radioanal. Nucl. Chem.*, 2017, **311**(3), 1781–1791, DOI: **10.1007/s10967-016-5123-8**.

202 M. Sumi, K. Abe, T. Kageyama, H. Nakazawa, A. Kurosawa, M. Yamamoto, et al., Verification of LSD spikes prepared in

Japan from a MOX source material, in *Proceedings of INMM 51st Annual Meeting (CD-ROM)*, Baltimore, USA, 2010.

203 M. Sumi, K. Abe, T. Kageyama and P. Mason, Pu standard material preparation in Japan, In *INMM 55th Annual Meeting*, Atalante, USA, 2014.

204 A.-M. Sanchez-Hernandez, K. Toth, Y. Aregbe, N. Banik, J. Bauwens, R. Buda, et al., Alternative nuclear certified reference materials for safeguards and industry, In *ESARDA 39th Annual Meeting 2017 Symposium*, Duesseldorf, Germany, 2017, Available from: https://publications.jrc.ec.europa.eu/repository/handle/JRC110509.

205 K. Toth, A.-M. S. Hernández, J. Bauwens, R. Buják, R. C. Marquez, R. Jakopič, et al., Embedding matrices to extend the shelf life of reference materials 1: Cellulose acetate butyrate, *Polym. Degrad. Stabil.*, 2022, **202**, 110024. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0141391022002075.

206 K. Toth, R. Buják, A. M. S. Hernández, J. Bauwens, R. C. Marquez, R. Buda, et al., Research on long-term stability of mixed U and Pu large-sized dried (LSD) spikes for fissile material control, *Prog. Nucl. Sci. Technol.*, 2018, **5**, 48–51. Available from: https://www.aesj.net/document/pnst005/data/048_051.pdf.

207 S. Konegger-Kappel, A. Koepf, R. Katona, M. R. Kilburn and S. F. Boulyga, A new era of plutonium assay and isotope ratio measurements at ultra-low levels in IAEA safeguards environmental swipe samples by isotope dilution MC-ICP-MS using a 244Pu spike, *J. Radioanal. Nucl. Chem.*, 2023, **332**(7), 2887–2904, DOI: **10.1007/s10967-023-08880-x**.

208 ASTM C1672-17 - Standard Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer.

209 S. Bürger, S. D. Balsley, S. Baumann, J. Berger, S. F. Boulyga, J. A. Cunningham, et al., Uranium and plutonium analysis of nuclear material samples by multi-collector thermal ionisation mass spectrometry: Quality control, measurement uncertainty, and metrological traceability, *Int. J. Mass Spectrom.*, 2012, **311**, 40–50. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380611004702.

210 C.-K. Kim, A. Bosko, D. Nakazawa, G. Duhamel, K. Mise, S. Hara, et al., A Combined Method of TIMS and HRGS for Rapid Determination of Pu Concentrations in Safeguards Samples at the On-Site Laboratory in the Rokkasho Reprocessing Plant, Symposium on International Safeguards: Building Future Safeguards Capabilities, In *Symposium on International Safeguards: Building Future Safeguards Capabilities*, Vienna, Austria, 2018, vol. 5–8.

211 U. Repinc, Application of strip isotope dilution analysis to safeguards samples containing low levels of uranium and plutonium, In *International Conference on Radioanalytical and Nuclear Chemistry (RANC-2023)*, Budapest from 7 – 12 May 2023.

<figure><img src="image_40.png" /></figure>
reference materials certified for the production date. Part I: methodology, preparation and target characteristics, *J. Radioanal. Nucl. Chem.*, 2016, **307**(2), 1077–1085, DOI: **10.1007/s10967-015-4227-x**.

192 C. Venchiarutti, Z. Varga, S. Richter, A. Nicholl, J. Krajko, R. Jakopič, et al., IRMM-1000a and IRMM-1000b: uranium reference materials certified for the production date based on the 230Th/234U radiochronometer. Part II: certification, *J. Radioanal. Nucl. Chem.*, 2016, **308**(1), 105–111, DOI: **10.1007/s10967-015-4368-y**.

193 S. J. Goldstein, M. T. Murrell and R. W. Williams, Half-life of 229Th, *Phys. Rev. C*, 1989, **40**(6), 2793–2795, DOI: **10.1103/PhysRevC.40.2793**.

194 H. Kikunaga, T. Suzuki, M. Nomura, T. Mitsugashira and A. Shinohara, Determination of the half-life of the ground state of 229Th by using 232U and 233U decay series, *Phys. Rev. C*, 2011, **84**(1), 014316, DOI: **10.1103/PhysRevC.84.014316**.

195 Z. Varga, A. Nicholl and K. Mayer, Determination of the 229Th half-life, *Phys. Rev. C*, 2014, **89**(6), 064310, DOI: **10.1103/PhysRevC.89.064310**.

196 R. M. Essex, J. L. Mann, R. Collé, L. Laureano-Perez, M. E. Bennett, H. Dion, et al., New determination of the 229Th half-life, *J. Radioanal. Nucl. Chem.*, 2018, **318**(1), 515–525.

197 G. R. Eppich, R. W. Williams, A. M. Gaffney and K. C. Schorzman, 235U-231Pa age dating of uranium materials for nuclear forensic investigations, *J. Anal. At. Spectrom.*, 2013, **28**(5), 666. Available from: http://xlink.rsc.org/?DOI=c3ja50041a.

198 K. C. Treinen, A. M. Gaffney, J. M. Rolison, K. M. Samperton, K. C. McHugh, M. L. Miller, et al., Improved protactinium spike calibration method applied to 231Pa-235U age-dating of certified reference materials for nuclear forensics, *J. Radioanal. Nucl. Chem.*, 2018, **318**(1), 209–219, DOI: **10.1007/s10967-018-6149-x**.

199 S. K. Aggarwal and D. Alamelu, A novel approach for the determination of 238Pu by thermal ionization mass spectrometry (TIMS) using interfering element correction methodology, *Int. J. Mass Spectrom.*, 2005, **241**(1), 83–88. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380604004300.

200 D. Alamelu, P. S. Khodade, P. M. Shah and S. K. Aggarwal, Investigations on atomic and oxide ion formation of plutonium and uranium in thermal ionization mass spectrometry (TIMS) for determination of 238Pu, *Int. J. Mass Spectrom.*, 2004, **239**(1), 51–56. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380604003756.

201 R. Jakopič, Y. Aregbe, S. Richter, E. Zuleger, S. Mialle, S. D. Balsley, et al., Verification measurements of the IRMM-1027 and the IAEA large-sized dried (LSD) spikes, *J. Radioanal. Nucl. Chem.*, 2017, **311**(3), 1781–1791, DOI: **10.1007/s10967-016-5123-8**.

202 M. Sumi, K. Abe, T. Kageyama, H. Nakazawa, A. Kurosawa, M. Yamamoto, et al., Verification of LSD spikes prepared in

Japan from a MOX source material, in *Proceedings of INMM 51st Annual Meeting (CD-ROM)*, Baltimore, USA, 2010.

203 M. Sumi, K. Abe, T. Kageyama and P. Mason, Pu standard material preparation in Japan, In *INMM 55th Annual Meeting*, Atalante, USA, 2014.

204 A.-M. Sanchez-Hernandez, K. Toth, Y. Aregbe, N. Banik, J. Bauwens, R. Buda, et al., Alternative nuclear certified reference materials for safeguards and industry, In *ESARDA 39th Annual Meeting 2017 Symposium*, Duesseldorf, Germany, 2017, Available from: https://publications.jrc.ec.europa.eu/repository/handle/JRC110509.

205 K. Toth, A.-M. S. Hernández, J. Bauwens, R. Buják, R. C. Marquez, R. Jakopič, et al., Embedding matrices to extend the shelf life of reference materials 1: Cellulose acetate butyrate, *Polym. Degrad. Stabil.*, 2022, **202**, 110024. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0141391022002075.

206 K. Toth, R. Buják, A. M. S. Hernández, J. Bauwens, R. C. Marquez, R. Buda, et al., Research on long-term stability of mixed U and Pu large-sized dried (LSD) spikes for fissile material control, *Prog. Nucl. Sci. Technol.*, 2018, **5**, 48–51. Available from: https://www.aesj.net/document/pnst005/data/048_051.pdf.

207 S. Konegger-Kappel, A. Koepf, R. Katona, M. R. Kilburn and S. F. Boulyga, A new era of plutonium assay and isotope ratio measurements at ultra-low levels in IAEA safeguards environmental swipe samples by isotope dilution MC-ICP-MS using a 244Pu spike, *J. Radioanal. Nucl. Chem.*, 2023, **332**(7), 2887–2904, DOI: **10.1007/s10967-023-08880-x**.

208 ASTM C1672-17 - Standard Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer.

209 S. Bürger, S. D. Balsley, S. Baumann, J. Berger, S. F. Boulyga, J. A. Cunningham, et al., Uranium and plutonium analysis of nuclear material samples by multi-collector thermal ionisation mass spectrometry: Quality control, measurement uncertainty, and metrological traceability, *Int. J. Mass Spectrom.*, 2012, **311**, 40–50. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1387380611004702.

210 C.-K. Kim, A. Bosko, D. Nakazawa, G. Duhamel, K. Mise, S. Hara, et al., A Combined Method of TIMS and HRGS for Rapid Determination of Pu Concentrations in Safeguards Samples at the On-Site Laboratory in the Rokkasho Reprocessing Plant, Symposium on International Safeguards: Building Future Safeguards Capabilities, In *Symposium on International Safeguards: Building Future Safeguards Capabilities*, Vienna, Austria, 2018, vol. 5–8.

211 U. Repinc, Application of strip isotope dilution analysis to safeguards samples containing low levels of uranium and plutonium, In *International Conference on Radioanalytical and Nuclear Chemistry (RANC-2023)*, Budapest from 7 – 12 May 2023.

<figure><img src="image_42.png" /></figure>
<figure><img src="image_41.png" /></figure>

212 M. H. A. Piro and K. Lipkina, Mining and milling, In *Advances in Nuclear Fuel Chemistry*, Elsevier, 2020, pp. 315–329. Available from: https://linkinghub.elsevier.com/retrieve/pii/B9780081025710000094.

213 A. Beaumais, A. Nonell, C. Caussignac, S. Mialle, G. Stadelmann, M. Janin, et al., Determination of the 144 Ce/238 U atomic ratio in spent nuclear fuel using double spike isotope dilution mass spectrometry, *J. Anal. At. Spectrom.*, 2022, 37, 1288–1297, DOI: **10.1039/D2JA00052K**.

214 A. Quemet, C. Maillard and A. Ruas, Determination of zirconium isotope composition and concentration for nuclear sample analysis using Thermal Ionization Mass Spectrometry, *Int. J. Mass Spectrom.*, 2015, **392**, 34–40.

215 S. Baghdadi, A. Quémet, E. Esbelin, Y. Manidren, S. Gracia, V. Dalier, et al., Zr precipitation kinetics in irradiated fuel dissolution solution by TIMS and ICP-MS: a combined study, *J. Radioanal. Nucl. Chem.*, 2017, **1–6**.

216 A. Inoue, Mechanism of the oxidative dissolution of UO2 in HNO3 solution, *J. Nucl. Mater.*, 1986, **138**(1), 152–154. Available from: https://linkinghub.elsevier.com/retrieve/pii/0022311586902710.

217 N. Desigan, N. Bhatt, M. A. Shetty, G. K. P. Sreekumar, N. K. Pandey, U. Kamachi Mudali, et al., Dissolution of nuclear materials in aqueous acid solutions, *Rev. Chem. Eng.*, 2019, **35**(6), 707–734, DOI: **10.1515/revce-2017-0063/html**.

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220 S. Van Winckel, R. Alvarez-Sarandes, D. Serrano Purroy and L. Aldave de las Heras, Assay data of spent nuclear fuel: the lab-work behind the numbers, *Front. Energy Res.*, 2023, **11**, DOI: **10.3389/fenrg.2023.1168460**.

221 M. Crozet and C. Rivier, Impact of dissolution on the uncertainty of spent fuel analysis, *J. Radioanal. Nucl. Chem.*, 2013, **298**(1), 325–336, DOI: **10.1007/s10967-013-2518-7**.

222 S. Röllin, Z. Kopatjtic, B. Wernli and B. Magyar, Determination of lanthanides and actinides in uranium materials by high-performance liquid chromatography with inductively coupled plasma mass spectrometric detection, *J. Chromatogr. A*, 1996, **739**(1–2), 139–149.

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225 A. Morgenstern, C. Apostolidis, R. Carlos-Marquez, K. Mayer and R. Molinet, Single-column extraction chromatographic separation of U, Pu, Np and Am, *Radiochim. Acta*, 2002, **90**(2), 81–85.

226 J. W. Grate, M. J. O'Hara, A. F. Farawila, M. Douglas, M. M. Haney, S. L. Petersen, et al., Extraction chromatographic methods in the sample preparation sequence for thermal ionization mass spectrometric analysis of plutonium isotopes, *Anal. Chem.*, 2011, **83**, 9086–9091.

227 K. Van Hoecke, J. Bussé, M. Gysemans, L. Adriaensen, A. Dobney and T. Cardinaels, Isolation of lanthanides from spent nuclear fuel by means of high performance ion chromatography (HPIC) prior to mass spectrometric analysis, *J. Radioanal. Nucl. Chem.*, 2017, **314**(3), 1727–1739.

228 H. Isnard, M. Aubert, P. Blanchet, R. Brennetot, F. Chartier, V. Geertsen, et al., Determination of 90Sr/238U ratio by double isotope dilution inductively coupled plasma mass spectrometer with multiple collection in spent nuclear fuel samples with in situ 90Sr/90Zr separation in a collision-reaction cell, *Spectrochim. Acta Part B At. Spectrosc.*, 2006, **61**(2), 150–156. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0584854705003435.

229 P. Regge and R. Boden, Determination of neodymium isotopes as burnup indicator of highly irradiated (U, Pu) O2 lmfbr fuel, *J. Radioanal. Chem.*, 1977, **35**(1), 173–184, DOI: **10.1007/BF02518224**.

230 E. A. Erin, V. N. Momotov, A. Y. Volkov, M. I. Khamdeev, V. N. Kupriyanov, A. Y. Shadrin, et al., Radiochemical analysis of a sample of mixed uranium–plutonium nitride fuel, *Radiochemistry*, 2017, **59**(4), 372–378, DOI: **10.1134/S1066362217040099**.

231 B. D. Roach, K. T. Rogers, N. A. Zirakparvar, J. S. Delashmitt, S. C. Metzger, B. T. Manard, et al., The need for speed – Burnup determination of spent nuclear fuel, *Talanta Open*, 2022, **6**, 100152. Available from: https://linkinghub.elsevier.com/retrieve/pii/S2666831922000698.

232 J. S. Kim, Y. S. Jeon, S. D. Park, Y. K. Ha and K. Song, Analysis of high burnup pressurized water reactor fuel using uranium, plutonium, neodymium, and cesium isotope correlations with burnup, *Nucl. Eng. Technol.*, 2015, **47**(7), 924–933, DOI: **10.1016/j.net.2015.08.002**.

233 ASTM International, *ASTM E321-20 - Standard Test Method for Atom Percent Fission in Uranium and Plutonium Fuel (Neodymium-148 Method)*, West Conshohocken, PA, USA, 2021.

234 K. Govers, L. Adriaensen, A. Dobney, M. Gysemans, C. Cachoir and M. Verwerft, Evaluation of the irradiation-averaged fission yield for burnup determination in spent fuel assays, *EPJ Nucl. Sci. Technol.*, 2022, **8**, DOI: **10.1051/epjn/2022018**.

235 H. Isnard, M. Granet, C. Caussignac, E. Ducarme, A. Nonell, B. Tran, et al., Comparison of thermal ionization mass spectrometry and Multiple Collector Inductively Coupled Plasma Mass Spectrometry for cesium isotope ratio measurements, *Spectrochim. Acta Part B At. Spectrosc.*, 2009, **64**(11–12), 1280–1286, DOI: **10.1016/j.sab.2009.10.004**.

236 V. Bulovič, J. Krtil, F. Sus, Z. Maksimovic and E. Klosova, Determination of the balance of the nuclear reactor fuel
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212 M. H. A. Piro and K. Lipkina, Mining and milling, In *Advances in Nuclear Fuel Chemistry*, Elsevier, 2020, pp. 315–329. Available from: https://linkinghub.elsevier.com/retrieve/pii/B9780081025710000094.

213 A. Beaumais, A. Nonell, C. Caussignac, S. Mialle, G. Stadelmann, M. Janin, et al., Determination of the 144 Ce/238 U atomic ratio in spent nuclear fuel using double spike isotope dilution mass spectrometry, *J. Anal. At. Spectrom.*, 2022, 37, 1288–1297, DOI: **10.1039/D2JA00052K**.

214 A. Quemet, C. Maillard and A. Ruas, Determination of zirconium isotope composition and concentration for nuclear sample analysis using Thermal Ionization Mass Spectrometry, *Int. J. Mass Spectrom.*, 2015, **392**, 34–40.

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232 J. S. Kim, Y. S. Jeon, S. D. Park, Y. K. Ha and K. Song, Analysis of high burnup pressurized water reactor fuel using uranium, plutonium, neodymium, and cesium isotope correlations with burnup, *Nucl. Eng. Technol.*, 2015, **47**(7), 924–933, DOI: **10.1016/j.net.2015.08.002**.

233 ASTM International, *ASTM E321-20 - Standard Test Method for Atom Percent Fission in Uranium and Plutonium Fuel (Neodymium-148 Method)*, West Conshohocken, PA, USA, 2021.

234 K. Govers, L. Adriaensen, A. Dobney, M. Gysemans, C. Cachoir and M. Verwerft, Evaluation of the irradiation-averaged fission yield for burnup determination in spent fuel assays, *EPJ Nucl. Sci. Technol.*, 2022, **8**, DOI: **10.1051/epjn/2022018**.

235 H. Isnard, M. Granet, C. Caussignac, E. Ducarme, A. Nonell, B. Tran, et al., Comparison of thermal ionization mass spectrometry and Multiple Collector Inductively Coupled Plasma Mass Spectrometry for cesium isotope ratio measurements, *Spectrochim. Acta Part B At. Spectrosc.*, 2009, **64**(11–12), 1280–1286, DOI: **10.1016/j.sab.2009.10.004**.

236 V. Bulovič, J. Krtil, F. Sus, Z. Maksimovic and E. Klosova, Determination of the balance of the nuclear reactor fuel
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237 J. R. Phillips, B. K. Barnes and T. R. Bement, Correlation of the Cesium-134/Cesium-137 Ratio to Fast Reactor Burnup, *Nucl. Technol.*, 1979, **46**(1), 21-29, DOI: **10.13182/NT46-21**.

238 L. Pibida, C. A. McMahon and B. A. Bushaw, Laser resonance ionization mass spectrometry measurements of cesium in nuclear burn-up and sediment samples, *Appl. Radiat. Isot.*, 2004, **60**(2-4), 567-570. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804303002975.

239 A. P. Smirnov-Averin, V. I. Galkov, I. G. Sheinker, V. P. Meshcheryakov, L. A. Stabenova and B. S. Kir'yanov, Determining burn-up in spent fuel elements, *Sov. J. At. Energy*, 1962, **11**(5), 1102-1104, DOI: **10.1007/BF01490500**.

240 M. Granet, A. Nonell, G. Favre, F. Chartier, H. Isnard, J. Moureau, et al., Cs-Ba separation using N2O as a reactant gas in a Multiple Collector-Inductively Coupled Plasma Mass Spectrometer collision-reaction cell: Application to the measurements of Cs isotopes in spent nuclear fuel samples, *Spectrochim. Acta Part B At. Spectrosc.*, 2008, **63**(11), 1309-1314.

241 J. S. Becker, R. S. Soma, K. L. Sutton, J. A. Caruso and H.-J. Dietze, Determination of long-lived radionuclides by inductively coupled plasma quadrupole mass spectrometry using different nebulizers, *J. Anal. At. Spectrom.*, 1999, **14**(6), 933-937. Available from: http://xlink.rsc.org/?DOI=a809252d.

242 S. F. Boulyga, Mass spectrometric analysis of long-lived radionuclides in bio-assays, *Int. J. Mass Spectrom.*, 2011, **307**(1-3), 200-210, DOI: **10.1016/j.ijms.2011.02.012**.

243 C. Bouvier-Capely, J. Ritt, N. Baglan and C. Cossonnet, Potentialities of mass spectrometry (ICP-MS) for actinides determination in urine, *Appl. Radiat. Isot.*, 2004, **60**(5), 629-633. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804304000132.

244 I. T. Platzner, J. S. Becker and H. Dietze, Stability Study of Isotope Ratio Measurements for Uranium and Thorium by ICP-QMS, *At. Spectr.*, 1999, **20**(February), 6-12.

245 W. S. Kinman, S. P. Lamont and R. E. Steiner, A rapid isotope dilution inductively coupled plasma mass spectrometry procedure for uranium bioassay, *J. Radioanal. Nucl. Chem.*, 2009, **282**(3), 1027-1030, DOI: **10.1007/s10967-009-0204-6**.

246 J. G. Arnason, C. N. Pellegri and P. J. Parsons, Determination of uranium isotope ratios in human urine by sector field inductively coupled plasma mass spectrometry for use in occupational and biomonitoring studies, *J. Anal. At. Spectrom.*, 2013, **28**(9), 1410. Available from: http://xlink.rsc.org/?DOI=c3ja50151e.

247 C. Li, K. Benkhedda, S. Tolmachev, L. Carty, R. Ko, D. Moir, et al., Measurement of 236U in human tissue samples using solid phase extraction coupled to ICP-MS, *J. Anal. At. Spectrom.*, 2010, **25**(5), 730. Available from: http://xlink.rsc.org/?DOI=b923909j.

248 H. Kurosaki, A. A. Tucker, S. E. Iden, S. M. Sexton, B. D. Gonzalez and G. R. Rao, Use of chromatographic pre-concentration for routine uranium bioassay analysis by ICP-MS, *J. Radioanal. Nucl. Chem.*, 2013, **298**(2), 1017-1022, DOI: **10.1007/s10967-013-2437-7**.

249 Y. Ni, J. Zheng, Q. Guo, W. Men, K. Tagami and S. Uchida, Rapid determination of ultra-trace plutonium isotopes (239Pu, 240Pu and 241Pu) in small-volume human urine bioassay using sector-field inductively coupled plasma mass spectrometry, *Anal. Chim. Acta*, 2018, **1000**, 85-92, DOI: **10.1016/j.aca.2017.10.012**.

250 E. Werner, P. Roth, I. Wendler, P. Schramel, H. Hellmann and U. Kratzel, Feasibility of ICP-MS for the assessment of uranium excretion in urine, *J. Radioanal. Nucl. Chem.*, 1997, **226**(1-2), 201-203, DOI: **10.1007/BF02063647**.

251 E. J. Wyse, J. A. MacLellan, C. W. Lindenmeier, J. P. Bramson and D. W. Koppenaal, Actinide bioassays by ICPMS, *J. Radioanal. Nucl. Chem.*, 1998, **234**(1-2), 165-170, DOI: **10.1007/BF02389766**.

252 Y. Shi, X. Dai, R. Collins and S. Kramer-Tremblay, Rapid determination of uranium isotopes in urine by inductively coupled plasma-mass spectrometry, *Health Phys.*, 2011, **101**(2), 148-153. Available from: https://journals.lww.com/00004032-201108000-00008.

253 Y. Shi, R. Collins and C. Broome, Determination of uranium, thorium and plutonium isotopes by ICP-MS, *J. Radioanal. Nucl. Chem.*, 2013, **296**(1), 509-515, DOI: **10.1007/s10967-012-2128-9**.

254 Y. Shi, X. Dai, C. Li, R. Collins, S. Kramer-Tremblay, R. Riopel, et al., ICP-MS method for Pu and Np isotopes in population monitoring by a micro-flow injection sample introduction system, *J. Anal. At. Spectrom.*, 2014, **29**(9), 1708-1713. Available from: http://xlink.rsc.org/?DOI=C4JA00105B.

255 P. J. Gray, L. Zhang, H. Xu, M. McDiarmid, K. Squibb and J. A. Centeno, Determination of 236U/238U and 235U/238U isotope ratios in human urine by inductively coupled plasma mass spectrometry, *Microchem. J.*, 2012, **105**, 94-100, DOI: **10.1016/j.microc.2012.07.004**.

256 H. Hernández-Mendoza, E. Chamizo, A. Delgado, M. García-León and A. Yllera, Comparison of methods and application of alpha spectrometry and mass spectrometry techniques for 239Pu determination in biological samples, *J. Anal. At. Spectrom.*, 2011, **26**(7), 1509. Available from: http://xlink.rsc.org/?DOI=c0ja00093k.

257 A. A. Reinhard, J. D. Inglis, R. E. Steiner, S. P. LaMont, A. R. Cardon, A. M. Wende, et al., An improved method for uranium separation from urine for rapid bioassay by inductively coupled plasma mass spectrometry, *J. Radioanal. Nucl. Chem.*, 2020, **326**(1), 611-619, DOI: **10.1007/s10967-020-07335-x**.

258 D. Clases and R. Gonzalez de Vega, Facets of ICP-MS and their potential in the medical sciences—Part 1: fundamentals, stand-alone and hyphenated techniques, *Anal. Bioanal. Chem.*, 2022, **414**(25), 7337-7361, DOI: **10.1007/s00216-022-04259-1**.

<figure><img src="image_42.png" /></figure>
burn-out process by gamma-spectrometry of fission products III, *J. Radioanal. Chem.*, 1983, **80**(1-2), 199-207, DOI: **10.1007/BF02517663**.

237 J. R. Phillips, B. K. Barnes and T. R. Bement, Correlation of the Cesium-134/Cesium-137 Ratio to Fast Reactor Burnup, *Nucl. Technol.*, 1979, **46**(1), 21-29, DOI: **10.13182/NT46-21**.

238 L. Pibida, C. A. McMahon and B. A. Bushaw, Laser resonance ionization mass spectrometry measurements of cesium in nuclear burn-up and sediment samples, *Appl. Radiat. Isot.*, 2004, **60**(2-4), 567-570. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804303002975.

239 A. P. Smirnov-Averin, V. I. Galkov, I. G. Sheinker, V. P. Meshcheryakov, L. A. Stabenova and B. S. Kir'yanov, Determining burn-up in spent fuel elements, *Sov. J. At. Energy*, 1962, **11**(5), 1102-1104, DOI: **10.1007/BF01490500**.

240 M. Granet, A. Nonell, G. Favre, F. Chartier, H. Isnard, J. Moureau, et al., Cs-Ba separation using N2O as a reactant gas in a Multiple Collector-Inductively Coupled Plasma Mass Spectrometer collision-reaction cell: Application to the measurements of Cs isotopes in spent nuclear fuel samples, *Spectrochim. Acta Part B At. Spectrosc.*, 2008, **63**(11), 1309-1314.

241 J. S. Becker, R. S. Soma, K. L. Sutton, J. A. Caruso and H.-J. Dietze, Determination of long-lived radionuclides by inductively coupled plasma quadrupole mass spectrometry using different nebulizers, *J. Anal. At. Spectrom.*, 1999, **14**(6), 933-937. Available from: http://xlink.rsc.org/?DOI=a809252d.

242 S. F. Boulyga, Mass spectrometric analysis of long-lived radionuclides in bio-assays, *Int. J. Mass Spectrom.*, 2011, **307**(1-3), 200-210, DOI: **10.1016/j.ijms.2011.02.012**.

243 C. Bouvier-Capely, J. Ritt, N. Baglan and C. Cossonnet, Potentialities of mass spectrometry (ICP-MS) for actinides determination in urine, *Appl. Radiat. Isot.*, 2004, **60**(5), 629-633. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0969804304000132.

244 I. T. Platzner, J. S. Becker and H. Dietze, Stability Study of Isotope Ratio Measurements for Uranium and Thorium by ICP-QMS, *At. Spectr.*, 1999, **20**(February), 6-12.

245 W. S. Kinman, S. P. Lamont and R. E. Steiner, A rapid isotope dilution inductively coupled plasma mass spectrometry procedure for uranium bioassay, *J. Radioanal. Nucl. Chem.*, 2009, **282**(3), 1027-1030, DOI: **10.1007/s10967-009-0204-6**.

246 J. G. Arnason, C. N. Pellegri and P. J. Parsons, Determination of uranium isotope ratios in human urine by sector field inductively coupled plasma mass spectrometry for use in occupational and biomonitoring studies, *J. Anal. At. Spectrom.*, 2013, **28**(9), 1410. Available from: http://xlink.rsc.org/?DOI=c3ja50151e.

247 C. Li, K. Benkhedda, S. Tolmachev, L. Carty, R. Ko, D. Moir, et al., Measurement of 236U in human tissue samples using solid phase extraction coupled to ICP-MS, *J. Anal. At. Spectrom.*, 2010, **25**(5), 730. Available from: http://xlink.rsc.org/?DOI=b923909j.

248 H. Kurosaki, A. A. Tucker, S. E. Iden, S. M. Sexton, B. D. Gonzalez and G. R. Rao, Use of chromatographic pre-concentration for routine uranium bioassay analysis by ICP-MS, *J. Radioanal. Nucl. Chem.*, 2013, **298**(2), 1017-1022, DOI: **10.1007/s10967-013-2437-7**.

249 Y. Ni, J. Zheng, Q. Guo, W. Men, K. Tagami and S. Uchida, Rapid determination of ultra-trace plutonium isotopes (239Pu, 240Pu and 241Pu) in small-volume human urine bioassay using sector-field inductively coupled plasma mass spectrometry, *Anal. Chim. Acta*, 2018, **1000**, 85-92, DOI: **10.1016/j.aca.2017.10.012**.

250 E. Werner, P. Roth, I. Wendler, P. Schramel, H. Hellmann and U. Kratzel, Feasibility of ICP-MS for the assessment of uranium excretion in urine, *J. Radioanal. Nucl. Chem.*, 1997, **226**(1-2), 201-203, DOI: **10.1007/BF02063647**.

251 E. J. Wyse, J. A. MacLellan, C. W. Lindenmeier, J. P. Bramson and D. W. Koppenaal, Actinide bioassays by ICPMS, *J. Radioanal. Nucl. Chem.*, 1998, **234**(1-2), 165-170, DOI: **10.1007/BF02389766**.

252 Y. Shi, X. Dai, R. Collins and S. Kramer-Tremblay, Rapid determination of uranium isotopes in urine by inductively coupled plasma-mass spectrometry, *Health Phys.*, 2011, **101**(2), 148-153. Available from: https://journals.lww.com/00004032-201108000-00008.

253 Y. Shi, R. Collins and C. Broome, Determination of uranium, thorium and plutonium isotopes by ICP-MS, *J. Radioanal. Nucl. Chem.*, 2013, **296**(1), 509-515, DOI: **10.1007/s10967-012-2128-9**.

254 Y. Shi, X. Dai, C. Li, R. Collins, S. Kramer-Tremblay, R. Riopel, et al., ICP-MS method for Pu and Np isotopes in population monitoring by a micro-flow injection sample introduction system, *J. Anal. At. Spectrom.*, 2014, **29**(9), 1708-1713. Available from: http://xlink.rsc.org/?DOI=C4JA00105B.

255 P. J. Gray, L. Zhang, H. Xu, M. McDiarmid, K. Squibb and J. A. Centeno, Determination of 236U/238U and 235U/238U isotope ratios in human urine by inductively coupled plasma mass spectrometry, *Microchem. J.*, 2012, **105**, 94-100, DOI: **10.1016/j.microc.2012.07.004**.

256 H. Hernández-Mendoza, E. Chamizo, A. Delgado, M. García-León and A. Yllera, Comparison of methods and application of alpha spectrometry and mass spectrometry techniques for 239Pu determination in biological samples, *J. Anal. At. Spectrom.*, 2011, **26**(7), 1509. Available from: http://xlink.rsc.org/?DOI=c0ja00093k.

257 A. A. Reinhard, J. D. Inglis, R. E. Steiner, S. P. LaMont, A. R. Cardon, A. M. Wende, et al., An improved method for uranium separation from urine for rapid bioassay by inductively coupled plasma mass spectrometry, *J. Radioanal. Nucl. Chem.*, 2020, **326**(1), 611-619, DOI: **10.1007/s10967-020-07335-x**.

258 D. Clases and R. Gonzalez de Vega, Facets of ICP-MS and their potential in the medical sciences—Part 1: fundamentals, stand-alone and hyphenated techniques, *Anal. Bioanal. Chem.*, 2022, **414**(25), 7337-7361, DOI: **10.1007/s00216-022-04259-1**.

<figure><img src="image_44.png" /></figure>