Application of Resonance Ionization Mass Spectrometry for Ultratrace

Article Analytical Chemistry is Application ofthe American published by Chemical Society. 1155 ResonanceSixteenth Ionization Street N.W., Washington, DC 20036 Mass Spectrometry for Publishedby by Georgetown American Subscriber access provided Society.Libraries University | LauingerChemical and Blommer Copyright © American Chemical Society. However, no copyright

Ultra-trace Analysis of Technetium Analytical Chemistry is published by the American

Pascal Schönberg, Christoph Chemical Society. 1155 Sixteenth Street N.W., Mokry, Jörg Runke, Daniela Washington, DC 20036 Published by Georgetown American Schönenbach, Nils Stöbener, Subscriber access provided by Society.Libraries University | LauingerChemical and Blommer Copyright © American Chemical Society. However, no copyright

Petra Thörle-Pospiech, Norbert Trautmann, and Tobias Reich Analytical Chemistry is

Anal. Chem., Just Accepted published by the American Chemical Society. 1155 Manuscript • DOI: 10.1021/ Sixteenth Street N.W., acs.analchem.7b01778 • Washington, DC 20036 Publication Date (Web): 24 Jul 2017 Published by American Subscriber access provided by Georgetown Society.Libraries University | LauingerChemical and Blommer Copyright © American Chemical Society. However, no copyright

Downloaded from http:// pubs.acs.org on July 28, 2017 Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., DC 20036 Just Accepted Washington, Publishedby by Georgetown American Subscriber access provided Society.Libraries University | LauingerChemical and Blommer Copyright © American Chemical Society. However, no copyright

“Just Accepted” manuscripts have been pee online prior to technical fo Analyticalediting, Chemistry formatting is by the American as a fre Society provides published “Just Accepted” Chemical Society. 1155 dissemination of scientific material as soon a Sixteenth Street N.W., appear in full in PDF formatDC accompanied by a Washington, 20036 Published by Georgetown American Subscriber access provided by fully peer reviewed, but should not be conside Society.Libraries University | LauingerChemical and Blommer Copyright © American Chemical Society. However, no copyright

readers and citable by the Digital Object Iden to authors. Therefore, the “Just Accepted” W Analytical Chemistry is is technica in the journal. After a manuscript published by the American Accepted” Web site and published Chemical Society. 1155 as an ASA Sixteenth Streettext N.W.,and/or graph changes to the manuscript Washington, DC 20036

Publishedby by Georgetown American Subscriber access provided Society.Libraries University | LauingerChemical and Blommer Copyright © American Chemical Society. However, no copyright

and ethical guidelines that apply to the jou or consequences arising from the use of info Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Publishedby by Georgetown American Subscriber access provided Society.Libraries University | LauingerChemical and Blommer Copyright © American Chemical Society. However, no copyright

Page 1 of 11 Analytical Chemistry

1 2 3 4 5 6 7

ACS Paragon Plus Environment

Analytical Chemistry

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 11

Application of Resonance Ionization Mass Spectrometry for Ultra-trace Analysis of Technetium Pascal Schönberg,∗ Christoph Mokry, Jörg Runke, Daniela Schönenbach, Nils Stöbener, Petra Thörle-Pospiech, Norbert Trautmann, and Tobias Reich∗ Institute of Nuclear Chemistry, Johannes Gutenberg University, Mainz, Germany E-mail: [email protected]; [email protected]

Abstract

into the environment, as for example during the Fukushima accident or by reprocessing plants such as Sellafield, 5,6 there can be similarly low concentrations needing to be determined. With 99g Tc being a pure β-emitter in combination with its long half-life, radiometric methods fail to determine ultra-trace amounts of 99g Tc. Therefore, a highly sensitive analytical method is required. Mass spectrometry can provide a sufficient limit of detection (LOD). However, there is a problem to be concerned about: Although techniques like inductively coupled plasma mass spectrometry (ICP-MS, LOD = 108 atoms) 7 and thermal ionization mass spectrometry (TIMS, LOD = 106 –107 atoms) 8,9 possess the desired sensitivity, these methods can be hampered by isobaric interference. 6,10–12 Therefore, extensive sample preparation is needed before the measurement to remove interfering isobars, for example, 99 Ru, the stable daughter of 99g Tc. Accelerator mass spectrometry (AMS, LOD = 105 –108 atoms) 13,14 is more effective in suppressing such interference, but is somewhat limited due to the need for a large accelerator facility. Resonance ionization mass spectrometry (RIMS) is a detection method with high sensitivity and considerable suppression of isobaric interference. 15 RIMS applies laser light tuned to successive atomic transitions to ionize thermally evaporated sample atoms. Due to the

This work shows the capability of Resonance Ionization Mass Spectrometry (RIMS) for the determination of 99g Tc at the ultra-trace level. The characterization of the prepared samples by X-Ray Photoelectron Spectroscopy (XPS) and optimization of the RIMS setup for this purpose as well as the application of the RIMS method to a soil sample are presented. 97 Tc was used as a tracer isotope to determine the amount of 99g Tc in a soil sample with RIMS. With 8.8 · 1010 atoms 97 Tc as a tracer, the concentration of 99g Tc amounts to 1.5 · 109 atoms / g dried sample material, demonstrating the sensitivity of the method. Furthermore, it could be shown that the 97 Tc solution contains 98 Tc as well. This is the first time 97,98,99g Tc have been simultaneously measured with RIMS.

Introduction The fission product 99g Tc (t1/2 = 2.1·105 a) is of major concern for the storage of spent nuclear fuel due to its radiotoxicity and the high mobility of the pertechnetate ion, TcO− 4 , in the environment. 1–3 Geochemical migration studies with Tc and a host rock of a possible nuclear waste repository have to be carried out at environmentally relevant Tc concentrations (10−8 –10−14 M). 4 Monitoring releases of 99g Tc


1

Page 3 of 11

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


uniqueness of the atomic structure of each element, resonance ionization enables, in combination with a mass spectrometer, a highly selective and an almost isobaric free detection of 99g Tc at the ultra-trace level. First Tc measurements with RIMS were reported by Downey et al. 16 using three-photon, two-color schemes, demonstrating the suitability of the method. They employed two tunable dye lasers with 20 Hz repetition rate to identify 22 unique ionization paths of 99g Tc. However, the experimental yield of Tc ions was ˜104 lower than the calculated one. Subsequent studies by Sattelberger et al. 17 applied a three-color, three-step resonant excitation via an autoionizing state of 99g Tc using three dye lasers with a repetition rate of 6.5 kHz. By measuring samples containing a known number of 99g Tc atoms on a Re filament, an overall efficiency of = 2·10−6 was obtained, corresponding to an LOD of ˜107 atoms. Similar values were achieved by Ames et al., 18 with a Tc laser ion source made of a tungsten cavity in combination with a Mattauch-Herzog mass spectrometer. With the cavity of the laser ion source made of ultrapure graphite, a lower detection limit of ˜105 atoms 99g Tc was obtained. 19 In the most recent study the dye laser system was replaced by three Ti:sapphire lasers with 10 kHz repetition rate. 20 Using samples with known amounts of 99g Tc atoms evaporated from a Re filament or placed inside the graphite cavity of a laser ion source, the overall efficiencies were 5·10−7 and 3·10−4 respectively. Although the efficiency for this laser ion source was higher, no corresponding LOD was reported. It should be noted, that in all RIMS studies only 99g Tc and no other Tc isotope has been resonantly excited and ionized. In one RIMS study 19 95m Tc (t1/2 = 60 d) was employed as a tracer to determine the yield of the chemical separations.

(Ti:sa) lasers are jointly pumped by a frequency doubled Nd:YAG laser (532 nm) at a 10 kHz repetition rate with about 15 W each, generating an output power of 1.4–2.5 W for each Ti:sa laser with a pulse length of 50 ns. A combination of a birefringent filter and an etalon is used for frequency selection, providing a spectral linewidth of 3–5 GHz. A fast high-voltage (HV) switching pockels cell for each Ti:sa laser allows the synchronization of the three laser pulses. For the first two steps of the excitation, the laser light of two Ti:sa lasers is frequency doubled using a BBO (β-BaB2 O4 ) crystal. Subsequently, the three beams are overlapped by means of polarization optics and dichroitic mirrors and are directed into the sample chamber (see Fig. 1), perpendicular to the beam of evaporating Tc atoms. The second part of the RIMS setup consists of a reflectron time-of-flight mass spectrometer (TOF-MS). Tc is eletrodeposited onto metal filaments 21 and evaporated by resistively heating the filaments. The atomic beam passes two repeller electrodes for background suppression before being ionized by the laser light. Positive and negative HV, respectively, are applied to the two electrodes, providing suppression of thermal ions and electrons, letting only neutral atoms pass, which results in an almost background-free mass spectrum. The laser ions thus produced are accelerated into the reflectron TOF-MS by a pulsed HV acceleration grid. After being separated by m / Z in the TOFMS, the ions are detected using a micro-channel plate detector.

Sample preparation Before the application of the method to environmental samples, the process of the detection of Tc by RIMS, from sample deposition to the measurement, was extensively characterized and optimized. The sample preparation was carried out by electrodeposition of 99g Tc from an electrolyte solution of 0.7 M ammonium oxalate (C2 H8 N2 O4 ) and 0.5 M sulfuric acid onto Re backings/filaments (3.5 x 10 mm2 ). For electrodeposition, the setup shown in Fig. 2

Experimental Section Experimental setup The RIMS setup at the Institute of Nuclear Chemistry is shown in Fig. 1; three Ti:sapphire


2


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 11

examine the species of the deposited Tc, XRay Photoelectron Spectroscopy (XPS) measurements were performed. The sample for XPS consisted of 3·1016 atoms (5.1 µg) of 99g Tc electrodeposited within an 8 mm spot onto Ta foil. This corresponds to an approximately 9 nm thick layer of Tc. XPS measurements were performed with a UNISPECS ESCA System (Specs Surface Nano Analysis GmbH, Berlin, Germany) in combination with a hemispherical energy analyzer, PHOIBOS 100 MCD. The spectra were recorded using non-monochromatic Mg Kα radiation (1253.6 eV) with analyzer pass energies of 50 eV and 13 eV for wide and narrow scans, respectively. During the measurements the vacuum was 10−9 –10−10 mbar. To remove thin surface layers, the sample was sputtered with Ar+ ions for ten minutes before each measurement (five in total) using the ion source IQE 11/35LP. The first measurement was performed prior to the sputtering. The electrostatic sample charging was corrected using either the C 1s peak (285.0 eV) of adventitious carbon or the Pt 4f7/2 peak (71.2 eV 22 ) of electrodeposited Pt (see below).

Figure 1: Schematic of the laser system and TOF-MS. was used. The electrolyte solution and analyte were poured into a PEEK cylinder with an 8 mm diameter opening at the bottom. A glass plate with a 3 mm diameter hole was placed underneath, confining the area on the metal backing where the technetium is deposited. Thus the filament is placed under the opening of the glass plate and in electrical contact with the titanium socket, which served as the cathode, whereas a platinum wire served as the anode. During the electrodeposition, the current was kept at I = 150 mA with a voltage of U = 20–25 V for two hours. Afterwards the filament was washed with deionized water and left to dry.

Characterization and optimization of the RIMS setup for 99g Tc analysis For resonance ionization of 99g Tc, a 3-color 3-photon scheme populating an autoionizing state (see Fig. 3), 20 was applied. Table 1 lists the laser wavelengths and laser powers for the steps. AI60452. 32cm-1 I P7. 12eV

841. 74nm

Figure 2: Schematic of the setup for electrodeposition of Tc.

48572. 10cm-1

J=5/ 2

4d65s

395. 15nm 23265. 32cm-1

J=7/ 2

4d55s5p

J=5/ 2

4d55s2

429. 83nm 0cm-1

Characterization of the electrodeposits

Figure 3: Excitation scheme for Tc.

For resonance ionization, it is crucial to have the analyte present as an atomic species. To ACS Paragon Plus Environment

3

Page 5 of 11

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1: Laser wavelengths and laser powers (mean values) used in this work.

material when heated. Many backing materials have been tested in different experiments regarding the technetium evaporation for resStep Transition wavelength [nm] Power [mW] onance ionization. 24 However, these tests were First 429.83 75 (SHG) performed with a different experimental setup, Second 395.15 100 (SHG) so all the metals listed above were tested as Ionizing 841.74 1400 backing materials for the detection of Tc by RIMS with our setup. General measurement procedure For this, a series of calibrated samples, each loaded with 2·1010 atoms 99g Tc, was prepared The RIMS measurements were started when on the three different backing materials and the pressure in the sample chamber was below measured. The overall efficiency (i.e., the ratio 5.5 ·10−6 mbar. A current was applied to the filbetween the number of ions detected and the ament, resistively heating it. At about 1300◦ C, introduced number of atoms, i.e., 2·1010 atoms) Tc started to evaporate and the filament was was determined for each measurement and avheated to a temperature where a stable count eraged for each material. rate of about 40 counts / s was achieved. Whenever the count rate decreased, the current was increased, heating the filament further until the Saturation measurements desired count rate was reached. This was repeated until the signal faded completely or the The next step of optimizing the RIMS process signal-to-noise ratio became insufficiently low. was the determination of the saturation powers For background correction, the laser for the first PSat for each excitation step. When the speexciting step was tuned out of resonance for 5 s, cific saturation power for an atomic transition leading to the vanishing of the Tc signal, with is reached, 50% of the maximal allowed amount only the counting background remaining. This of atoms are in the excited state. In resonance was done in alternation with the lasers being in ionization, the population of the excited state resonance with the transitions, for 20 s. The directly corresponds to the detected ion signal. background measurement was later corrected For these measurements, a filament loaded with for the time difference. 99g Tc was heated until a high and steady ion count rate was achieved. Then, the light of one Choice of the backing material of the three Ti:sa lasers was stepwise attenuated using a gray scale, while the other two reAn important factor in the evaporation of Tc mained at full power, and the resulting count from the filament is the backing material itself. rate was recorded. This was repeated for each Depending on the enthalpies of adsorption and of the three steps. diffusion, an element will evaporate differently After characterizing the best backing material from different materials during the heating pro(Re) and the saturation powers, another series cess. This, along with the heat stability of the of rhenium filaments loaded with 2·1010 atoms given material, must be taken into account to 99g Tc were measured with longer measurement find the best backing. times between the heating intervals for backTheoretical calculations by Rossbach and Eichground reduction to determine the optimized ler 23 propose Re, W, and Ta to be the materials mean overall efficiency of our RIMS setup for best suited for the evaporation of technetium. the ultra-trace analysis of 99g Tc. Due to the large negative values of the adsorption enthalpy, technetium is strongly bound to 97 Tc tracer the surface, and will hardly evaporate. Large values for the enthalpy of solution indicate the For quantification of 99g Tc with RIMS, another tendency of the element to diffuse into the bulk isotope of the same element is needed. It ACS Paragon Plus Environment

4


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

needs to be accessible with resonance ionization through atomic states lying close to those of the analyte, so that tuning to the respective resonant transitions of the isotopes is feasible. 97 Tc (t1/2 = 4.21·106 a) is a suitable candidate for this, and we are in possession of a solution containing this rare isotope. In order to use it in our RIMS measurements, the isotope shift (IS) between 99g Tc and 97 Tc had to be determined. This was done in collaboration with the Institute of Physics at Johannes Gutenberg University Mainz. The IS was determined to be 312 MHz for the first transition and 102 MHz for the second transition. 25 With our laser bandwidth being several orders of magnitude broader, no detuning of the laser wavelengths for each isotope is needed when performing a measurement with our RIMS setup. The isotopes can be ionized simultaneously. This was confirmed in measurements using samples containing the same amounts of 99g Tc and 97 Tc, resulting in similar count rates. During these measurements it was discovered that the 97 Tc tracer solution also contains 98 Tc, to one-tenth of the amount of the tracer isotope. The presence of 98 Tc (t1/2 = 4.0·106 a) was confirmed with γ-ray spectrometry, which showed the two strong lines of 98 Tc at 652.4 keV and 745.4 keV. 26 The RIMS measurements of the pure 97 Tc stock solution did not show any 99g Tc, so it was not present or at least was significantly below our LOD. Since we are concerned with 99g Tc and 97 Tc, the contamination with 98 Tc does not present a problem.

Page 6 of 11

After cooling, the remaining solid was separated by centrifugation, washed twice, and discarded. The resulting solutions were concentrated to 20 mL and left until the next day, after addition of 2 mL H2 O2 (to assure that technetium is present as Tc(VII)) and HCl. The solution was then neutralized and for the purification of Tc, ion exchange chromatography R was applied using a Dowex AG 1x8 resin in a 5 x 150 mm column. For this, the Tc solution was put in the column and after washing steps with 2 x 5 mL H2 O, followed by 2 x 5 mL 0.5 M HCl and 2 x 5 mL H2 O for the removal of remaining interfering elements, the technetium was eluted with 4 x 5 mL 10 M HNO3 . The yield of this step was ˜80%. After evaporating the eluate, it was used for electrodeposition of the Tc, as described before.

Results and discussion XPS measurements The survey spectrum of the untreated sample surface showed intense XPS peaks of C, O, Tc and Pt. The C 1s signal originates from adventitious carbon and was used as a binding energy reference with Eb (C 1s) = 285.0 eV. The detection of the Pt 4f lines can be explained by electrodeposition of Pt that was dissolved from the anode wire during electrolysis. The shape of the Pt 4f7/2 line remained unchanged during subsequent surface treatments by Ar+ sputtering for 10–40 min. Prior to Ar+ sputtering, the binding energy, Eb , of Pt 4f7/2 was 71.1 ± 0.1 eV, which agrees well with the literature value for Pt metal (Eb,lit (Pt 4f) = 71.2 eV). 22 In subsequent measurements, this Pt 4f7/2 binding energy was used to correct for the electrostatic surface charging, since the C 1s signal had disappeared after 10 min of Ar+ sputtering. For the untreated sample surface that had been exposed to air, the Tc 3d5/2 spectrum contained contributions from metallic and oxidized Tc species. The Tc 3d5/2 binding energies of 256.6 ± 0.1 eV and 259.6 ± 0.1 eV agree well with those of Tc(IV) (256.6 eV)

Chemical preparation of the soil sample The sample used for the RIMS measurement was a soil sample taken in Rhineland-Palatinate that had been artificially spiked in the laboratory with an unknown amount of 99g Tc. For a RIMS sample, 1 g of the sample material was dried and ashed, and 5 g Na2 CO3 , 5 g K2 CO3 , and 30 µL 97 Tc tracer solution (8.8 · 1010 atoms) were added and thermal decomposition at 720 ◦ C by soda-potash fusion was performed with a yield of ˜40%. The solid was dissolved in boiling millipore water.


5

Page 7 of 11

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and Tc(VII) (259.8 eV) 271 . The oxidized Tc surface species were removed completely by 10 min Ar+ sputtering. The resulting Tc 3d spectrum could be modeled by two components with Eb (Tc 3d5/2 ) = 254.0 eV and Eb (Tc 3d3/2 ) = 257.7 eV (Fig. 4). These binding energies agree with those reported for metallic Tc (Eb,lit (Tc 3d5/2 ) = 253.9 eV and Eb,lit (Tc 3d3/2 ) = 257.5 eV). 28 The Tc 3d spectrum did not change during subsequent measurements after additional 10 min intervals of sputtering. We conclude that below an approximately 6 nm thick Tc oxide layer (see Supporting Information (SI) Calc. S-1), the remaining Tc is electrodeposited as a metal that also contains Pt. The observation of metallic Tc deposits agrees with the results of powder X-ray diffraction (XRD) and X-ray absorption fine structure spectroscopy (XAFS) measurements performed by Mausolf et al 29 on electrodeposited Tc on gold foils from 1 M sulfuric acid solutions. They reported the reduction of TcO4 – and formation of hexagonal Tc metal deposits.

+ 1 0 ’ Ar Sp u t t e r i n g

Figure 4: Narrow region spectrum of the Tc 3d lines after ten minutes of Ar+ sputtering. power. Thus, for background correction, a mean background (BG) per channel (one channel corresponding to 10 ns time of flight) was used.

RIMS Saturation powers

Table 2: Mean efficiencies () and limits of detection (LOD) for the detection of 99g Tc by RIMS with Ta, W, and Re backings; 2·1010 atoms 99g Tc were used for each deposition.

The saturation powers were determined to be PSat1 = 28(5) mW for excitation step 1 and PSat2 = 71(16) mW for excitation step 2. With the achievable laser powers, both steps can be saturated. The curve for the ionizing step, however, still showed a linear trend: i.e., this step cannot be fully saturated.

LOD

Choice of backing material and efficiency of the setup

Ta filament 4.08(4)·10−7 8·107 atoms

W filament 4.60(4)·10−7 5·107 atoms

Re filament 5.76(1)·10−6 7·106 atoms

As can be seen, with Re as the backing material, about one order of magnitude in efficiency was gained. Therefore, all subsequent samples were prepared using Re filaments. From the measurements with Re backing, the average efficiency and LOD for the ultra-trace analysis of 99g Tc by RIMS are = 8(1) · 10−6 and LOD = 3 · 106 atoms (≈ 0.5 fg), respectively. Details on the calculation of the LOD is given in SI (Calc. S-2).

The results of the efficiency measurements using the three different backing materials are given in Tab. 2. During the measurements the background showed a statistically distributed, homogenous behavior in the Tc mass range. This behavior was confirmed by tuning the lasers out of resonance while remaining at full 1

The binding energies have been referenced to Eb (C 1s) = 285.0 eV.


6


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

RIMS measurement of the soil sample

Page 8 of 11

atoms into an autoionizing state. After accelerating the laser ions into a reflectron TOFMS, the Tc ions are counted with a microchannel plate detector. The overall efficiency for the detection of 99g Tc deposited on a filament was measured with this RIMS setup resulting in = 8(1) · 10−6 . This does not differ significantly from previous measurements performed in Mainz. 17,18,20 The determined LOD of ˜3 · 106 atoms (≈ 0,5 fg) compares favorably to other techniques like TIMS and AMS. In order to apply RIMS to the quantitative ultra-trace analysis of 99g Tc in a soil sample, 97 Tc was used for the first time as a tracer. Due to the small IS of 312 MHz between the isotopes 97 Tc and 99g Tc and the spectral bandwidth of 3–5 GHz of the laser light of our RIMS system, both Tc isotopes were measured simultaneously, allowing the application of the method to environmental samples. Since the 97 Tc tracer solution contained also 98 Tc, all three Tc isotopes, i.e., 97 Tc, 98 Tc, and 99g Tc, have been simultaneously measured with RIMS for the first time. An improvement in the system’s performance is expected with a new sample holder currently under development. Acknowledgement

The chemical preparation and measurement of the soil sample was performed as described in the experimental section. The obtained mass spectrum is shown in Fig. 5. Recalculating from the count rates and initially added quantity of 97 Tc tracer, the amount of 99g Tc was determined to be 1.5(1) · 109 atoms of 99g Tc / g dried sample material. The efficiency for this measurement was = 1.80(1) · 10−7 with an LOD of 3 · 108 atoms. These values differ from those retrieved from a measurement of a directly electrodeposited Tc sample. The drop in overall efficiency by a factor ˜40 cannot be explained by losses in the chemical separation of the Tc that amount to approximately 30% (see above). During the RIMS measurement of this soil sample, technical difficulties with the sample holder occured, which prevented us from heating the filament beyond ˜1450◦ C due to an increasing background signal.

Figure 5: Mass spectrum of the soil sample; the tracer isotope 97 Tc is displayed in red, the analyte 99g Tc and accompanying 98 Tc in green. Note: For a better visualization of the data, the signals for 99g Tc and 98 Tc have been multiplied by five.

This work was funded by the Federal Ministry of Economics and Technology (BMWi) under contract number 02E10981. The authors would like to thank Prof. Dr. N. Bings for providing the 97 Tc tracer solution, J. Drebert for the XPS measurements, T. Kron, S. Raeder, and M. Franzmann for the laser spectroscopy on the isotope shift of Tc, Prof. Dr. K. Wendt and Dr. G. Passler for discussions, and Dr. S. Amayri and C. Willberger for ICP-MS measurements of the 97 Tc tracer solution.

Conclusions

Supporting Information Available

The RIMS setup in the Institute of Nuclear Chemistry in Mainz, consisting of three Ti:sa lasers, which are pumped by a frequency doubled Nd:YAG laser with a repetition rate of 10 kHz, has been used to resonantly excite 99g Tc

Formulae and calculations of the thickness of the Tc oxide layer based on the XPS measurement and for the determination of the LOD of the RIMS.


7

Page 9 of 11

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References

di Tada, M. L.; Day, J. P. Nucl. Instrum. Methods Phys. Res., Sect. B 2000, 168, 427 – 436.

(1) Schwochau, K. Angew. Chem. 1964, 76, 9–19.

(14) Bergquist, B.; Marchetti, A. A.; Martinelli, R. E.; McAninch, J. E.; Nimz, G. N.; Proctor, I. D.; Southon, J. R.; Vogel, J. S. Nucl. Instrum. Methods Phys. Res., Sect. B 2000, 172, 328 – 332.

(2) Benedict, M.; Levi, H.; Pigford, T. Nuclear Engineering, 2nd ed.; McGraw-Hill, 1981. (3) Lieser, K. H.; Bauscher, C. Radiochim. Acta 1987, 42, 205–213.

(15) Trautmann, N.; Passler, G.; Wendt, K. Anal. Bioanal. Chem. 2004, 378, 348–355.

(4) Bradbury, H. M.; Baeyens, B. Far-Field Sorption Data Bases for Performance Assessment of a L/ILW Repository in an Undisturbed Palfris Marl Host Rock. 1997; PSI Report, ISSN 1019-0643.

(16) Downey, S. W.; Nogar, N. S.; Miller, C. M. Int. J. Mass Spectrom. Ion Processes 1984, 61, 337 – 345.

(5) Karcher, M.; Gerland, S.; Harms, I. H.; Iosjpe, M.; Heldal, H. E.; Kershaw, P. J.; Sickel, M. J. Environ. Radioact. 2004, 74, 185–198.

(17) Sattelberger, P.; Mang, M.; Hermann, G.; Riegel, J.; Rimke, H.; Trautmann, N.; Ames, F.; Kluge, H.-J. Radiochim. Acta 1989, 48, 165–169.

(6) Shi, K.; Hou, X.; Roos, P.; Wu, W. Anal. Chim. Acta 2012, 709, 1 – 20.

(18) Ames, F.; Brumm, T.; Jaeger, K.; Kluge, H. J.; Suri, B. M.; Rimke, H.; Trautmann, N.; Kirchner, R. Appl. Phys. B: Lasers Opt. 1990, 51, 200–206, 10.1007/BF00405739.

(7) Sumiya, S.; Morita, S.; Tobita, K.; Kurabayashi, M. J. Radioanal. Nucl. Chem. 1994, 177, 149–159.

(19) Passler, G.; Erdmann, N.; Hasse, H.U.; Hermann, G.; Huber, G.; Köhler, S.; Kratz, J.; Mansel, A.; Nunnemann, M.; Trautmann, N.; Waldek, A. Kerntechnik 1997, 62, 2–3.

(8) Rokop, D. J.; Schroeder, N. C.; Wolfsberg, K. Anal. Chem. 1990, 62, 1271– 1274. (9) Dixon, P.; Curtis, D. B.; Musgrave, J.; Roensch, F.; Roach, J.; Rokop, D. Anal. Chem. 1997, 69, 1692–1699.

(20) Wendt, K.; Geppert, C.; Mattolat, C.; Passler, G.; Raeder, S.; Schwellnus, F.; Wies, K.; Trautmann, N. Anal. Bioanal. Chem. 2012, 404, 2173–2176.

(10) E. Eroglu, A.; W. Mcleod, C.; S. Leonard, K.; McCubbin, D. J. Anal. At. Spectrom. 1998, 13, 875–878.

(21) Trautmann, N.; Folger, H. Nucl. Instrum. Methods Phys. Res., Sect. A 1989, 282, 102 – 106.

(11) McCartney, M.; Rajendran, K.; Olive, V.; G. Busby, R.; McDonald, P. J. Anal. At. Spectrom. 1999, 14, 1849–1852.

(22) Williams, G. P. X-Ray Data Booklet, 1.1 Electron Binding Energies. Lawrence Berkeley National Laboratory, Center for X-Ray Optics and Advanced Light Source, LBNL/PUB-490 Rev. 3, 2009.

(12) Mas, J.; Garcia-Leon, M.; Bolivar, J. P. Nucl. Instrum. Methods Phys. Res., Sect. A 2002, 484, 660 – 667. (13) Fifield, L. K.; Carling, R. S.; Cresswell, R. G.; Hausladen, P. A.;

(23) Rossbach, H.; Eichler, B. Zentralinstitut fr Kernforschung Rossendorf 1984, 527, 12, 14–15.


8


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(24) Ames, F.; Kluge, H.-J.; Otten, E.-W.; Suri, B. M.; Venugopalan, A.; Herrmann, G.; Rimke, H.; Trautmann, N.; Kirchner, R.; Eichler, B. Ann. Phys. 1991, 503, 1–14. (25) Raeder, S.; Kron, T.; Heinke, R.; Henares, J. L.; Lecesne, N.; Schönberg, P.; Tr¨ umper, M.; Wendt, K. Hyperfine Interact. 2017, 238, 15. (26) Singh, B.; Hu, Z. Nuclear Data Sheets 2003, 98, 335 – 513. (27) Wester, D. W.; White, D. H.; Miller, F. W.; Dean, R. T.; Schreifels, J. A.; Hunt, J. E. Inorg. Chim. Acta 1987, 131, 163 – 169. (28) Köver, L.; Cserny, I.; Brabec, V.; Fiser, M.; Dragoun, O.; Novak, J. Phys. Rev. B 1990, 42, 643–647. (29) Mausolf, E.; Poineau, F.; Hartmann, T.; Droessler, J.; Czerwinski, K. J. Electrochem. Soc. 2011, 158, 32–35.


9

Page 10 of 11

Page 11 of 11

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Graphical TOC Entry

Principle of the analysis of Tc with RIMS.


10

Application of Resonance Ionization Mass Spectrometry for Ultratrace

Recommend Documents