Journal of Nuclear and Radiochemical Sciences, Vol. 18, pp. 1-4, 2018

Notes
Preparation of Iodine-129 Standard Solutions for Triple Quadrupole ICP-MS
Maki Hondaa,*, Yuichi Takakub, Yasuyuki Shikamoric, Hiroyuki Matsuzakid and Keisuke Suekie
aGraduate School of Pure and Applied Sciences University of Tsukuba, 1-1-1 Tennodai, Tsukuba-shi, Ibaraki, 3058577, Japanb
Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho-mura, Aomori, 039-3212, JapancAgilent Technologies, Chemical Analysis, Japan Application Center, Takakura, Hachioji, Tokyo, 192-8510, JapandMicro Analysis Laboratory, Tandem accelerator (MALT), The University Museum, The University of Tokyo, 2-1116 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japane
Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba-shi, Ibaraki 305-8577,
Japan

Received January 5, 2018; Accepted January 12, 2018: Published online February 2, 2018
Accelerator mass spectrometry (AMS) has been recognized as the most sensitive analytical method for the isotopic ratio 129I/127I, and its limit of detection reaches as low as 129I/127I < 2×10 -14. Recently triple quadrupole ICP-MS(ICP-MS/MS) is becoming an alternative analytical method for the rather high isotopic ratio range, 129I/127I > 10 -8.
Absolute ICP-MS/MS measurements require reliable standard materials for calibration. In this study, 129I standard solutions “tRIC-1” and “tRIC-2” were prepared from a laboratory-stored 129I solution and the 129I radioactivity standard of NIST SRM 4949d, respectively. The isotopic ratios of 129I/127I were determined to be (6.54 ± 0.23)
× 10 -5 for tRIC-1 and (3.41 ± 0.12) × 10 -6 for tRIC-2 from the measurement results of AMS (129I/127I ratio) andICP-MS/MS (127I concentration). From the 129I and 127I concentrations each calibration line in ICP-MS/MS wasused to calculate the 129I/127I isotopic ratios which were (6.51 ± 0.26) × 10 -5 for tRIC-1 and (3.34 ± 0.13) × 10 -6 fortRIC-2. These isotopic ratios of 129I/127I agree with the value from AMS. It was proved that the two home-madestandard solutions could be measured using the latest ICP-MS/MS and reliable isotopic ratios of 129I/127I wereobtained.

1. IntroductionA large amount of 129I (t1/2 = 1.57 × 107 y) has been introduced into the terrestrial environment through nuclear weapon
testing, spent nuclear fuel reprocessing operations, and nuclear
accidents, and this has led to a wide range of isotopic ratios of129 127
I/ I from 10 -14 to 10 -1 in the terrestrial environment.1-4 The129
I determination in natural samples is commonly carried out
at big facilities with radiochemical neutron activation analysis(RNAA) and accelerator mass spectrometry (AMS) capabilities. RNAA is based on neutron activation by 129I (n, γ) 130I,
which is determined by measurement of γ rays at 536 keV.
The limit of detection (LOD) of RNAA is 10 -10 – 10 -9 for
129 127
I/ I isotopic ratios.5,6 Thus, AMS has been the only method
for the determination of wide range of 129I/127I isotopic ratios.
The LOD of 129I/127I ratio achieved by AMS < 2 × 10 -14.7 AMS
is applied as a certification method for the isotopic standard
materials provided from the National Institute of Standards
and Technology (NIST, USA) because AMS is the most reliable method for determination of the 129I/127I isotopic ratios.
The 129I/127I ratios have been normalized by standard referencematerials provided by PRIME Lab at Purdue University.8
Recent developments in analytical techniques using the triple quadrupole inductively coupled plasma mass spectrometry(ICP-MS/MS) have allowed observation of high 129I contents(LOD of ICP-MS/MS for the 129I/127 I isotopic ratio > 10 -8 ismore than six orders of magnitude higher than the LOD ofAMS for the ratio).9-11 The ICP-MS/MS has a compact benchtop design and is a simple system resulting that is easier tomaintain than RNAA or AMS systems. The ICP-MS/MS pro*Corresponding author: Maki HONDA, E-mail: m-honda@ied.tsukuba.ac.jp, Fax: +81-29-853-6237

vides versatile applications by combining it with other devices
such as gas or ion chromatographs and lasers and it offers highsample throughput for routine measurements. It may also be
useful for screening of high 129I content samples. In ICP-MS/MS, the dominant interferences are 129Xe+ from argon plasma
gas and polyatomic species, 127 IH 2+ (127 ID +), 97 MoO 2+ and113
CdO+, from 129I-containing sample. The 129Xe+ signal can beefficiently lowered by reaction with O2 to a negligible level (ca.
1 count per second).12-14 But the severe polyatomic interference of 127IH 2+ (127ID +) cannot be entirely removed, meaningthat the LOD of 129I is restricted to 0.5 μBq mL-1 (corresponding to 129I/127I = 10 -8).9-11 This dominant interference can bepartially decreased by taking an integration time for m/z =128
prior to m/z =129. The standard reference material with certified isotopic ratio is essential to the accurate 129I analysis byICP-MS/MS. However, there is no commercial isotopic standard reference material, and that has prevented widespread useof ICP-MS/MS for 129I environmental studies.
In this study, two types of home-made 129I standard solutions for ICP-MS/MS, designated “tRIC-1” and “tRIC-2”, wereprepared from a laboratory-stored 129I solution and the 129I
radioactivity standard of NIST SRM 4949d, respectively, andreliable isotopic ratios of 129I/127I were obtained.
2. Experimental
2.1. Standard solution preparation. The first standardsolution, tRIC-1, was prepared from a laboratory-stored 129I
solution that included approximately 0.1 M KOH, 0.1 M
K 2SO3, 1 mg mL-1 127I and 0.5 Bq mL-1 129I, and the calculated
atomic 129I/127I ratio was 7 × 10 -5. A 10.1-g amount of the 129I
solution was added to a PFA bottle (1000 mL) and diluted with
2% tetramethyl ammonium hydroxide (TMAH) solution© 2018 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 02/02/2018

2J. Nucl. Radiochem. Sci., Vol. 18, 2018

Honda

Figure 1. Schematic drawing explaining the AMS measurement of targets prepared from tRIC-1 and tRIC-2. Five or four solid AgI targets andstandard materials were pressed into aluminum cathodes. These aluminum cathodes were then mounted on a target wheel so they could be analyzed at five times sequentially. The 129I/127I measurement results of each target were averaged to get a beam time.

(TAMAPURE-AA, Tama Chemicals) to 1015 g. Therefore,
the 129I of tRIC-1 was calculated to be about 5 mBq g-1.
The second standard solution, tRIC-2, was prepared fromthe 129I radioactivity standard of NIST SRM 4949d thatincluded 0.007 M Na2SO3 and 2.747 ± 0.03 kBq g-1 129I. A 10.1mg amount of NIST SRM 4949d was mixed with 54 g ofiodine solution (Orion Ionplus Application Solution IodineStandard 0.1 M, Thermo Scientific) and 1.3 g Na2SO3 (analytical grade, Wako Pure Chemical). This mixed solution was
diluted with deionized purified water to 1510 g in a PFA bottle(2000 mL), and thus the calculated atomic 129I/127I ratio was(3.33 ± 0.04) × 10 -6. The 129I value of tRIC-2 was calculated tobe 18.4 ± 0.2 mBq g-1.
All solutions prepared in this study were diluted with deionized purified water (18.2 MΩ cm) obtained from a PURELAB
Ultra (ELGA) purifier.
2.2. Preparation of AMS targets and determination of
the 129I/127I ratio by AMS. A 0.1-mL amount of tRIC-1 wastransferred to a glass beaker, and this solution was mixed with
0.1 mL of 1% Na 2SO3 and 698 mg of iodine (55 mL of Orion
Ionplus, Application Solution Iodide Standard 0.1 M) to dilutethe 129I/127I ratio for AMS. The iodine in mixed solution wasprecipitated as an AgI with 3 mL of 50% AgNO3 (analyticalgrade, Wako Pure Chemical) and 0.2 mL of conc. HNO3(TAMAPURE-AA, Tama Chemicals). A 0.1-mL amount oftRIC-2 was treated as the same manner of tRIC-1 and theiodine was precipitated as an AgI. The precipitate was washedwith 10% ammonia water followed by washing with purewater three times. The precipitate was collected by centrifugation at 3000 rpm and decanting, and then dried at 60°C.
The dried precipitate AgI was pressed into an aluminum cathodes as the ion source targets of the AMS measurements. TheAMS measurements were conducted at the The University ofTokyo’s Micro Analysis Laboratory, Tandem accelerator(MALT). The samples (that is, the dried precipitate AgI in thealuminium cathode targets) prepared from the tRIC-1 standard
solution were measured in five different beam times, while theanalogous samples prepared from the tRIC-2 standard solution
were measured in one beam time. In each beam time, 4 or 5
cathode targets were mounted on the target wheel and measured at five times. The measured 129I/127I ratios were averaged to get the result for the beam time (Figure 1). The typicalmeasurement time for one cathode target was 5 minutes. The
LOD of the 129I-AMS system at MALT is typically 129I/127I < 2× 10 -14. 7 The 129I/127I ratios were all normalized by the standard material of Z94-0596 provided by the PRIME Lab atPurdue University. The nominal value 129I/127I = 6.54 × 10 -11 isTABLE 1: The experimental parameters and configuration of ICP-MS/MS
Sample introduction system
PlasmaRF power
Plasma gas flow rate
Auxiliary gas flow rate
Nebulizer gas flow rate
Solution uptake rate
Spray chamber temperature
Sampling depthLensExtraction lens 1, 2
Cell focus
Cell entrance
Cell exit
Deflection
Plate bias
Cell
O2 gas flow rate
Octopole bias
Octopole RF
Energy discrimination
OtherIntegration time form/z = 127, 128, 129
Repetition, sweep

Parameters
1550 W
15 L min-1
0.90 mL min-1
1.01 mL min-1
0.1 mL min-1
2°C
8 mm
0 V, -200 V
2.0 V
-50 V
-60 V
2.0 V
-60 V
0.8 mL min-1-5.0 V
200 V-7.0 V
0.5, 1.0, 10 s
10, 100 times

used in MALT. The nominal value has a potential uncertaintyof 2.9% (2σ) that comes from the source material.8 The 129I/127I
ratio and 129I concentration (mBq g-1) of the home-made 129I
standard solutions were calculated by the 129I/127I ratio fromAMS and the 127I amounts (atoms) from ICP-MS/MS. Total
uncertainty for the 129I/127I ratio was 3.6% (2 σ) that was evaluated from the statistical errors of AMS (2.0%, 2 σ), ICP-MS/
MS (<1%, 2 σ), and the total uncertainty of standard material(2.9%, 2 σ). Total uncertainty for the 129I concentration wasalso 3.6% (2 σ) and was evaluated in the same manner.
2.3. 129I measurement with ICP-MS/MS. The experimental parameters and configuration of the ICP-MS/MS (AgilentTechnologies, model 8800) are summarized in Table 1. The
set of a micro-uptake ty pe glass concentric nebulizer(MiroMistTM) and a quartz torch with a 1.5 mm internal diam-Preparation of Iodine-129 Standard Solutions for Triple Quadrupole ICP-MS

J. Nucl. Radiochem. Sci., Vol. 18, 2018

3Figure 2. Measured isotopic ratios of 129I/127I of tRIC-1 standard solution obtained by AMS. Shown data were corrected values considering theisotopic dilution effect by the carrier. Open gray circles shows the 129I/127I ratios obtained from the measurement for each cathode and closed
black circles show the averaged 129I/127I values calculated from each beam time. The 129I/127I isotopic ratio obtained by AMS is denoted as a solid
red line that was evaluated as the averaged value for five beam times. Broken red lines show the total uncertainty of 3.6% (2 σ) for the 129I/127I
isotopic ratio. The solid blue line shows the 129I/127I ratio obtained by ICP-MS/MS. The broken blue line shows the total uncertainty of 4.0% (2 σ)for the 129I/127I ratio.

Figure 3. Measured isotopic ratios of 129I/127I of tRIC-2 standard solution obtained by AMS. Shown data here were corrected values considering
the isotopic dilution effect by the carrier. Open gray circles show the 129I/127I ratios obtained from the measurement for each cathode. The 129I/127I
ratio obtained by AMS is denoted as a solid red line that was evaluated as an averaged value for five cathodes. Broken red lines show the total
uncertainty of 3.6% (2 σ) for the 129I/127I isotopic ratio. The solid blue line shows the 129I/127I ratio obtained by ICP-MS/MS. The broken blue line
shows the total uncertainty of 4.0% (2 σ) for the 129I/127I ratio.

eter injector was applied for sample introduction.9 Plasma andcarrier gases were 99.99% Ar, and reaction gas was 99.999%
O2. The isotopic ratios of 129I/127I of the two home-made 129I
standard solutions were determined by the 127I and 129I concentrations using the calibration lines for 127I and 129I. These calibration lines were obtained from multiple dilutions of theiodine standard solution (Orion Ionplus, Application Solution
Iodine Standard 0.1 M) and the 129I radioactivity standard solution from NIST SRM 4949d. 127 I was measured under thesame conditions as for 129I. The total measurement time wasabout 5 minutes for one sample. Total uncertainty of the129 127
I/ I ratio was 4.0% (2σ) and that was evaluated from thestatistical errors of the 127 I measurement (<1%, 2σ), the 129I
measurement (3.8%, 2σ) and the total uncertainty of NIST
SRM 4949d (1.1%, 2σ). The uncertainty of the 129I concentration was 4.0% (2σ) and that evaluated from the statistical errorof the 129I measurement and the total uncertainty of NIST
SRM 4949d.

3. Results and Discussion
The AMS results were corrected to the original isotopic
ratios of the home-made standard solutions considering theisotopic dilution effect by the added stable iodine carrier. A
good reproducibility was obtained in the 129I-AMS at MALT,
as shown in Figure 2. The averaged isotopic 129I/127 I ratio
results for five beam times ranged from (6.51 ± 0.05) × 10 -5 to(6.57 ± 0.03) × 10 -5. The 129I/127I ratio of tRIC-1 was the averaged value for the five beam times and 6.54 × 10 -5 with total
uncertainty of 3.6%. The 127 I concentration of tRIC-1 wasdetermined to be 9.51 ± 0.04 μg g-1 (2σ) from the calibrationline in Figure 4 (top). The 129I concentration of tRIC-1 wascalculated by AMS and ICP-MS/MS results to be 4.13 mBq g-1(corresponding to 0.622 ng g-1) with total uncertainty of 3.6%.
The isotopic 129I/127I ratio of tRIC-2 was evaluated from theresult of one beam time measurement to be 3.41 × 10 -6 withtotal uncertainty of 3.6% (Figure 3). The concentration of 127Iof tRIC-2 was determined to be 831 ± 7 μg g-1 (2σ). The con-4J. Nucl. Radiochem. Sci., Vol. 18, 2018129

Honda-1

centration of I was determined to be 18.8 mBq g (corresponding to 2.83 ng g-1) with total uncertainty of 3.6%.
The 129I concentrations for tRIC-1 and tRIC-2 were determined by the 129I calibration line obtained from ICP-MS/MS(Figure 4, bottom). The 129I concentration was 0.629 ng g-1(corresponding to 4.11 mBq g-1) with total uncertainty of 4.0%
for tRIC-1. For tRIC-2, the 129I concentration was 2.81 ng g-1(corresponding to 18.4 mBq g-1) with total uncertainty of 4.0%.
The isotopic ratios of 129I/127I for tRIC-1 and tRIC-2 were calculated to be (6.51 ± 0.26) × 10 -5 and (3.34 ± 0.13) × 10 -6 ,respectively, from the determined each concentrations. TheLODs (3σ, n = 10) for 127I and 129I were 0.18 ng g-1 and 0.10 pg
g-1, respectively, while the background equivalent concentrations for 127I and 129I were 1.0 ng g-1 and 0.28 pg g-1, respectively.
The 129I value of tRIC-1 from ICP-MS/MS (4.11 ± 0.16 mBq-1g ) agreed reasonably with that from AMS (4.13 ± 0.15 mBqg-1). The 129I value of tRIC-2 from ICP-MS/MS (18.4 ± 0.7mBq g-1) agreed well with that calculated from the theoreticalvalue (18.4 ± 0.2 mBq g-1). The AMS result (18.8 ± 0.7 mBqg-1) also showed good agreement with the theoretical value.
The isotopic ratio of 129I/127I of the home-made 129I standard
solutions measured by ICP-MS/MS agreed well with those by
AMS. This result indicated that two suitable and reliable isotopic ratio 129I/127I standard solutions for ICP-MS/MS, tRIC-1
and tRIC-2, were obtained from this study for the iodine isotope concentration and isotopic ratio determinations. The statistical uncertainty from ICP-MS/MS was around 2% for 129I
concentration under the studied conditions. However, the statistical uncertainty by ICP-MS/MS can be improved byincreasing the integration time.
4. Conclusions
Two types of the home-made 129I standard solutions “tRIC1” and “tRIC-2” were prepared in this study and they gave
reasonably reliable values for the isotopic ratio of 129I/127I andeach isotope concentration in ICP-MS/MS measurements.
The home-made 129I standard solutions were prepared using
the laboratory-stored 129I solution for tRIC-1and the 129I radioactivity standard of NIST SRM 4949d for tRIC-2. The 127 I
concentrations were determined by ICP-MS/MS to be 9.51 ±0.04 μg g-1 for tRIC-1 and 831 ± 7 μg g-1for tRIC-2. From theAMS determinations for tRIC-1, the 129I concentrations andthe isotopic ratios of 129I/127I were 4.13 ± 0.15 mBq g-1 and (6.54± 0.23) × 10 -5, respectively, and for tRIC-2, they were 18.8 ±0.7 mBq g-1 and (3.41 ± 0.12) × 10 -6, respectively. These homemade solutions were demonstrated to be applicable standards
when using ICP-MS/MS.
Acknowledgements
The authors gratefully acknowledge Ms. K. Nakano ofAgilent Technologies for her technical support and usefulcomments on this study. The authors also would like to thank
MALT staff members for their technical support in the AMS
measurements. A part of this work was supported by JSPS
KAKENHI Grant Number 16J05248 and Sasakawa Scientific
Research Grant (Grant Number 27-342) from The Japan
Society.
References(1) G. Snyder, A. Aldahan, G. Possnert, Geochem. Geophys.
Geosyst. 11, 1 (2010).
(2) R. Michel, J. Handl, T. Ernst, W. Botsch, S. Szidat, A.
Schmidt, D. Jakob, D. Beltz, L.D. Romantschuk, H.-A.
Synal, C. Schnabel, J.M. López-Gutiérrez, Sci. TotalEnviron. 340, 35 (2005).

Figure 4. Calibration lines for 127I (top) and 129I (bottom). The 127I
and 129I plots were obtained from the iodine standard solution (OrionIonplus, Application Solution Iodine Standard 0.1 M) and the 129I
radioactivity standard solution (NIST SRM 4949d), respectively.

(3) U. Rao and U. Fehn, Geochim. Cosmochim. Acta. 63,
1927 (1999).
(4) P.J. Magno, T.C. Reavey, J.C. Apidianakis, ORP/SID 72-5,
US Environmental Protection Agency, 1972.
(5) Y. Muramatsu, Y. Ohmomo, D. Christoffers, J. Radioanal.
Nucl. Chem. Art. 83, 353 (1984).
(6) X. Hou, H. Dahlgaard, B. Rietz, U. Jacobsen, S. P. Nielsen,
A. Aarkrog, Analyst. 124, 1109 (1999).
(7) H. Matsuzaki, C. Nakano, Y.S. Tsuchiya, S. Ito, A. Morita,
H. Kusuno, Y. Miyake, M. Honda, A.T. Bautista VII, M.
Kawamoto, H. Tokuyama, Nucl. Instrum. Methods Phys.
Res. 361, 63 (2015).
(8) P. Sharma, D. Elmore, T. Miller, S. Vogt, Nucl. Instrum.
Methods Phys. Res. 123, 347 (1997).
(9) T. Ohno, Y. Muramatsu, C. Toyama, N. Kazumi S. Kakuta,H. Matsuzaki, Anal. Sci. 29, 271 (2013).
(10) T. Ohno, Y. Muramatsu, Y. Shikamori, C. Toyama, N.
Okabe, H. Matsuzaki, J. Anal. At. Spectrom. 28, 1283
(2013).
(11) Y. Shikamori, K. Nakano, N. Sugimaya, S. Kakuta,Application note 5991-0321EN, Agilent, Japan. (2012).
(12) G. C. Eiden, C. J. Barrinaga, and D. W. Koppenaal, RapidCommun. Mass Spectrom. 11, 37 (1997).
(13) D. R. Bandura, V. I. Baranov, and S. D. Tanner, J. Am.
Soc. Mass Spectrom. 13, 1176 (2002).
(14) A. V. Izmer, S. F. Boulyga, and J. S. Becker, J. Anal. At.
Spectrom. 18, 1339 (2003).