Radiation Environment and Medicine 2022 Vol.11, No.1 7–15

Regular Article

Rapid Chemical Separation Protocol for Optimized 90Sr Determination
by ICP-MS in Water Samples for Radiological Incident
Hirofumi Tazoe1*, Yuto Tomisaka 2, Naofumi Akata1, Ben Russell3, Peter Ivanov3,
Masahiro Hosoda1, 2 and Shinji Tokonami1
1

Institute of Radiation Emergency Medicine, Hirosaki University, Hirosaki, Aomori, 036-8564, Japan
2
Graduate School of Health Sciences, Hirosaki University, Aomori, 036-8564, Japan
3
National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, United Kingdom
Received 15 September 2021; revised 24 November 2021; accepted 6 December 2021

Research has been conducted to speed up and simplify the 90Sr analysis method in water samples
based on the importance of 90Sr measurement for environmental monitoring in the event of aradiological incident. To optimize the measurement with ICP-MS, which enables rapid analysis, we
examined the pre-treatment conditions when cation exchange resin chromatography and Sr Resinsolid-phase extraction were used. Sr was quantitatively recovered by cation exchange resin from
1 L synthetic water samples, and anionic components such as Ge and Se were efficiently removed.
In addition, under the elution condition using 3 M HNO3, it is possible to suppress the elution of
Zr with a small volume of eluent. The eluate from cation exchange chromatography can be used
for successive solid-phase extraction of Sr-Resin directly, which provides further Sr purificationand concentration sufficient for 90Sr determination by ICP-MS. Verification was performedon real samples including high hardness bottled water. We confirmed that the results of thesynthetic sample analysis were reproduced, and that Sr was quantitatively recovered (96-100%)and coexisting elements were removed sufficiently so as not to interfere with the measurementof 90Sr. 90Sr was concentrated by a factor of 100 during chemical separation procedure without any
evaporation step. Processing time for more than 10 samples was 3 hours, which is fast enough for
emergency response in the case of radiological incident.
Key words: 90Sr, chemical separation, ICP-MS, water, radiological incident

1. Introduction
Radioactive strontium (90Sr) is one of the major fission
products produced by thermal neutron fission of 235U
and 239Pu. Its chemical similarity to Ca causes theradionuclide to accumulate in hard tissue of biota. In*Hirofumi Tazoe: Institute of Radiation Emergency Medicine, Hirosaki University,
66-1 Hon-cho, Hirosaki, Aomori, 036-8564, Japan
E-mail: tazoe@hirosaki-u.ac.jp
Copyright © 2022 by Hirosaki University. All rights reserved.

addition, 90Sr can impact aquatic ecosystems via groundwater and river water due to its high solubility in thewater phase. Historically, radioactive contaminations of
the Techa River in the South Urals of Russia1-3) and theColumbia River around the Hanford site in the USA 4)
have occurred. These facts have led researchers torecognize the importance of establishing rapid androutine radiological monitoring of 90Sr in water for
detecting accidental releases to the environment andavoiding ingestion by the public. In the event of a nuclear
emergency, the WHO Codex guideline levels specifies

8

Hirofumi Tazoe et al./ Radiation Environment and Medicine 2022 Vol.11, No.1 7–15

that the activity concentration might not be greater than
100 Bq/kg for 90Sr for infant food and 100 Bq/kg for 90Sr
for food other than infant food.
The governments of some Asian and African countries
are promoting nuclear power generation, meaning
the number of power plants are likely to increase andtherefore simple, rapid and efficient analytical methods
for radionuclides are in high and increasing demand.
Radionuclide release accidents can affect widespreadareas and present issues of trans-border contamination forneighboring countries that cannot be ignored. To respondto emergency radiological incident, it is important
to develop procedures that are compatible with theequipment that individual laboratories commonly have.
Inductively coupled plasma mass spectrometry (ICPMS) is a promising analytical method to replace radiation
measurements from the viewpoint of high sample
throughput for long-lived radionuclides5-7). Progress
in ICP-MS for 90Sr analysis has been notable since the2011 severe accident at the Fukushima Daiichi Nuclear
Power station8). ICP-MS equipped with collision reaction
cell (CRC) technology can significantly remove spectralinterference from 90Zr9-11). In addition, various options suchas a desolvating introduction system and an automatedseparation system can be adopted to enhance analytesensitivity and sample throughput, respectively. Takagai
et al.12) used ICP-MS combined with the automatedseparation system for 90Sr analysis of contaminated soilby the accident of the Fukushima Daiichi Nuclear stationand showed it to be an indispensable analytical tool.
However, instrumental limit of detection (LOD) of ICPMS in our laboratory is 500 Bq/L, which is higher thanthe WHO Codex guideline levels. There is still a need to
improve procedures for pre-concentration and chemical
separation to optimize ICP-MS and to reduce the sample
preparation time.
In the case of ICP-MS measurement, 90Sr + can beaffected by isobaric interfere from 90Zr+ and polyatomic
interference from 74Ge16O+ and 74Se16O+ 13). Attention
should also be paid to the peak tailing effect from 88Sr+.
An abundant amount of stable Sr can suppress ICP-MS
sensitivity14). CRC using oxygen gas is effective to lower90
Zr+ interference through the formation of 90Zr16O+, whilst
the reaction of O2 with 90Sr+ does not proceed. Ohno et al.
reported that 90Zr + interfering ions in a test solution
containing 1 µg/L Zr were removed by the reaction using
oxygen gas and they had a contribution of about 2 counts
per second14).
High Sr content samples could lead to underestimation
by suppressing sensitivity and overestimation of90
Sr due to the peak tailing effect. The degree of thesignificance for the peak tailing effect is evaluated using
the interference signal at m/z = 90 and 90Sr+/88Sr+ signal
ratio. Abundance sensitivity for quadrupole ICP-MS andsector field ICP-MS are on the orders of 10–9 14) and 10–7 10),respectively. The stable Sr concentrations in riverwater and groundwater analyzed in this study are in
the range of 1–100 µg/L. One study has found that theconcentrations of Sr varied from ~6 to 800 µg/L, andaveraged ~60 µg/L in a river water system15), whereasanother study has found that the global river average was
78 µg/L16).
The Sr separation method has been well studied within
the context of radiometric Sr detection through isolationfrom other beta emitting radionuclides. For radiogenic Sr
isotope ratio analysis (86Sr/87Sr) used for geological dating,the separation focus has been focused on the removal ofmajor components including Ca, which is a homologous
element, and the removal of Rb, which is an interfering
element during isotope analysis. Chemical separation
methods suitable for radiochemical measurements havebeen summarized by Vadja and Kim17) and Shao et al.18).
Several methods have been investigated, including
precipitation 19, 20), ion exchange 19) and solid phaseextraction chromatography 21-24). The application of
extraction chelating Sr-resin (Triskem International) overthe last decade has shown excellent Sr selective affinity.
While radiometric measurements require attention tointerference from other beta nuclides, mass spectrometry
is different as it removes interference from stable isotopes
such as 90Zr.
We investigated a rapid and simple analytical method
for monitoring drinking water in radiological incidents.
The method was optimized for rapid ICP-MS and
therefore eliminated evaporation step, which is timeconsuming and can introduce contamination. For thispurpose, we developed a two-stage chemical separation
method using cation exchange chromatography forpreconcentration and Sr-resin extraction chromatography
for further Sr purification. The method was designed
so that the sample could be introduced directly into thecolumn and the resulting Sr solution could be measured
directly by ICP-MS.
2. Experimental
2.1 Materials and Chemicals
Ultra-pure water was obtained using a Milli-Q Reference
system (Merck Millipore, USA). Laboratory materials,
including bottles and tubing were soaked in 1 M HCl andthen rinsed in the ultra-pure water. The ultra-pure water
was also used to prepare all solutions. Nitric acid wascommercially obtained electro-industry grade acid (Kanto
Chemical, Japan). XSTC-622 multi-elemental standard
solution (SPEX CertiPrep, USA) was used to obtain thecolumn chromatograms for Na, Ca, Mg, Sr, among otherelements. Atomic adsorption analysis grade Zr, Se and Ge
standard solutions were also used.

Hirofumi Tazoe et al./ Radiation Environment and Medicine 2022 Vol.11, No.1 7–15
A)

9

B)

Fig. 1. Schematic illustration of chromatography processes. A) Cation exchange chromatography column isconsisted of 5 mL of cation exchange resin, DOWEX1X8, and polypropylene empty column. Water sample is loaded
to the column by peristaltic pump. B) Sr resin extraction chromatography column is prepacked 2 mL, connected toextension funnel to increase in loading volume up to 30 mL.

Cation exchange resin (5 mL, AG50W-X8, 100-200
mesh, Bio-Rad, USA) was filled into a polyethylene
column (Muromac mini-column M) (Fig. 1A). The cationexchange column was cleaned by rinsing with 30 mL of
8 M HNO3 and 30 mL of 0.05 M HNO3. Then, 20 mL of 4
M HNO3 was added to the column prior to introducing
sample solution.
Extraction chelating resin, 2 mL Sr Resin column(100-150 µm particle size, Part No. SR-C20-A), waspurchased from Eichrom Technology (USA). Sr Resin isfunctionalized by 4,4′(5′)-di-t-butylcyclohexano 18-crown-6(crown ether) in 1-octanol, which specifically adsorb Sr2+
ion in HNO3 medium by recognizing the ionic radius. An
extension funnel was connected to the Sr Resin column toincrease in the sample reservoir volume to about 30 mL(Fig. 1B). Sr Resin column was rinsed with 10 mL of 0.05
M HNO3 and 10 mL of 4 M HNO3 prior to use.
To examine the separation procedure, synthetic
standard samples were prepared from SPEX XSTC-622
multi-elemental standard solution (10 mg/L). All analyteelements were present in a 5 µg amount of a 1 L water
sample. 2.5 µg of Sr, Na, Ca, Mg, and Rb from XSTC622 multi-elemental standard solution and 100 µg of Zr
were doped and adjusted to a volume of 30 mL in 3 M
HNO3 to the standard sample for cation exchange resin
chromatography and Sr Resin chromatography.
Real water samples were used to validate developed
method. The river water samples were collected in the
Ukedo River of Fukushima Prefecture on 9th July 2019and stored in plastic bottles after filtration with 0.45 µm
pore membrane and acidification (pH< 2). The tap water
sample was collected in Hirosaki City, Aomori, Japan.

Fig. 2. Chemical procedure for 90Sr in water sample by two-stage
chromatography using cation exchange and Sr resins prior to ICP-MS
determination.

Two kinds of bottled water (BW) were purchased fromthe market and acidified.
2.2 Equipment
To analyze the effectiveness of chemical separation,
concentrations of Sr and other elements were measured
using a tandem quadrupole ICP-MS (Agilent 8800 ICPQQQ, Agilent, USA) installed at Hirosaki University.

10

Hirofumi Tazoe et al./ Radiation Environment and Medicine 2022 Vol.11, No.1 7–15

Fig. 3. Elution profile of Ca, Sr, Cs, Ge, Se, and Zr during sample loading step in cation exchange resin
chromatography. Flow rates were 40, 60, and 90 mL/min.

A)

B)

Fig. 4. Elution profiles of A) Sr and B) Zr obtained using various
concentration of HNO3 in cation exchange resin chromatography.

2.3 Cation exchange chromatography
Figure 2 summarizes the two-stage chemical separation
method we followed for 90 Sr in water sample bychromatography using cation exchange and Sr selective
resins. Figure 1 offers schematic drawings of the columns
and pump used in the chromatographic processes.
Measured volume of concentrated HNO3 was added
to the 1 L water sample solution to make a solution
concentration of 0.1 M HNO3. This was introduced into
the cation exchange resin column using a peristaltic
pump (Masterflex L/S Precision Pump). Flow rates were
adjusted to 10, 20, 30, 40, 60, 90 mL/min; slowest flow
required up to 100 minutes for this pre-concentration withthe 1 L water sample. Retained cations including Sr2+ were
eluted by 2, 3 and 4 HNO3 by gravity flow to optimize Srelution and to minimize Zr concentration. Eluates werecollected in 100 mL fractions during the sample loading
step and 5 mL fractions during the elution step.
2.4 Sr Resin extraction chromatography
T he e l u t ed S r f r a c t ion f r om ca t ion e x c ha n g echromatography was directly introduced into the Sr Resincolumn because Sr is strongly associated at 2 – 4 M HNO3(kʼ > 4025)). On the other hand, Zr is not adsorbed by Sr
Resin. Kavasi et al.22) reported that decontamination factor
for Zr was more than 104 with 87% Sr yield.
The flow rate tested ranged from 0.2 mL/min to
0.9 mL/min, which reflected sample volume remaining
in column reservoir due to gravity flow. After the column
was rinsed with 10 mL of 8 M HNO3 to remove interfering
elements, Sr was eluted by 0.05 M HNO3.

Hirofumi Tazoe et al./ Radiation Environment and Medicine 2022 Vol.11, No.1 7–15

11

Table 1. Chemical yields, concentration factor (CF) for Sr and Decontamintaion factor (DF) for other elements during chemical sepration processes
Element

Sr
Na
Mg
K
Ca
Ge
Se
Rb
Zr
Cs
Ba

Cation exchange resin chromatography
Chemical yield
CF
Sample load
Elution
DF
0.1%
97.6%
33
87.0%
5.4%
82.6%
0.3%
99.1%
98.1%
53.2%
0.2%
36.4%
0.6%

13%
93%
17%
100%
<3%
<6%
44%
0.6%
60%
100%

0.23
0.03
0.17
0.03
>1
>0.5
0.07
5
0.05
0.03

Sr Resin chromatography
Chemical yield
Sample load
Rinse
0.1%
0.2%
88%
85%
69%
78%
94%
94%
92%
73%
93%
14%

3. Results and discussion
3.1 Cation exchange chromatography
Monovalent cations such as Cs +, and Rb + were notdetected in the initial sample loading, while relative
concentrations increased above the loaded volume of
300 mL (Fig. 3 and Supplementary Fig. S1). Relative
concentrations for Ge, Se and W were close to 1, whichindicated they did not associate with cation exchange
resin due to presence of anionic species in 0.1 M HNO3
medium. Sr and Zr elutions were not observed during thesample loading step, which indicated they were retainedin the cation exchange column. Divalent cations (e.g., Ca2+,
Ba2+, Pb2+), and U showed similar profiles.
For the 90 mL/min flow rate as the sample loading
condition, attention should be paid to the connection
between the tubing and resin column; it can be released
accidentally by the increased pressure. Therefore, wechoose 60 mL/min flow rate for sample loading.
Sr yields in 40 mL of 2 M HNO3 for elution were in
the range of 94–97% (Fig. 4A). Additional elution wasneeded for quantitative collection. Sr elutions by 3 M and
4 M HNO3 had similar profiles and these elutions werecompleted by 30 mL of eluate as could be seen from
Figure. 4A. Sr yield increased to 97 – 98% and 98 – 99%,
respectively, at the 3 M and 4 M HNO3 concentration.
The relative concentration of Zr gradually increased
with eluate volume in 3 M and 4 M HNO3 elution
conditions (Fig. 4B). The Zr residual rate was 0.6% by
30 mL of eluate for the 3 M HNO3 condition (Table 1).
The relative concentration of Zr for the 4 M HNO3
condition was about 10 times larger than that in 3 M
HNO3 condition. The Zr chemical yield reached 10 - 15%
by 30 mL of eluate. The distribution coefficient of Sr usinga Sr Resin is more than 50 in 3 M HNO3 25). 3 M HNO3
was selected for Sr elution from the viewpoint of getting
a low Zr residual rate of the initial amount and reducing

10%
5.5%
27%
20%
5%
5%
8%
4%
5%
68%

Elution
97.9%

CF
DF
2.9

<0.1%
0.4%
<2%
0.6%
0.07%
0.17%
0.04%
0.04%
0.05%
19%

> 300
92
>17
55
470
200
770
870
680
2

Total
Chemical yield
95.6%

CF
DF
96

< 0.01%0.3%< 0.4%
0.6%< 0.002%< 0.01%0.02%
0.0002%
0.03%
19%

>160
3
>3
2
>470
>100
52
4100
34
0.05

the sample volume of load solution for the subsequent Sr
Resin extraction chromatography.
Effectiveness of removal for interference elements
can be expressed by the decontamination factor. The
decontamination factor (DF) of a coexisting element isgiven in Equation 1:
C0
DF = ――
Cs

Equation 1

where C0 is the concentration in the sample before theseparation and C s is the concentration in the sample
after the separation. The chemical yield for Zr was 0.6 %,which corresponded to a DF Zr of 5. If Zr concentration
in a water sample is low, the separated Sr fraction fromthe cation exchange resin can potentially be used for90
Sr determination by ICP-MS. However, evaporation anddissolution processes are required to adjust the HNO3
concentration for ICP-MS measurements. In addition,
attention must be paid to contamination of interference
elements from the laboratory environment during any
evaporation process.
Despite the limited Zr decontamination, the sample
volume could be reduced from 1 L to 30 mL throughcation exchange chromatography, which corresponded
to a concentration factor (CF) of 33 (Table 1). The
decontamination factors of Zr (DF Zr), Ge (DFGe), Se (DFSe)
during cation exchange chromatography were 5,> 1, and> 0.5, respectively.
3.2 Sr Resin extraction chromatography
The eluate from cation exchange resin chromatography
could be introduced into the Sr Resin column directly.
No elution of Sr during sample loading and rinse
steps indicated that Sr was adsorbed on Sr Resin (Fig.
5A). Sr was then eluted in 0.05 M HNO3. The relative
concentration of Sr rose to 8 at 6 mL of eluate. 10 mL of
0.05 M HNO3 yielded 98% Sr recovery.

12

Hirofumi Tazoe et al./ Radiation Environment and Medicine 2022 Vol.11, No.1 7–15

A)

B)

Fig. 5. Elution profiles of A) Sr, Ca and Ba and B) Zr, Ge, and Se in
Sr Resin extraction chromatography.

Zr, Ge and Se flowed through the Sr Resin column due
to their weak affinity to Sr Resin (Fig. 5B). The relative Zr
concentration sharply decreased to 4 orders of magnitude
lower than that of the loaded sample for the rinsing stepby 8 M HNO3. In the early elution step, a small Zr peakand Ge and Se peaks were observed. But Zr chemicalyield was only 0.04% in the Sr fraction. The DFs were 870
for Zr, 470 for Ge and 200 for Se.
The combined chemical separation of cation exchange
resin and Sr Resin chromatography achieve DF Zr of4100. CRC-ICP-MS operated in the oxygen reaction
mode could provide Zr+ removal efficiency 104 relative
to the sensitivity for the no oxygen gas condition. If theZr concentration can be reduced to 1 ppt by chemical
separation, CRC-ICP-MS is enough to reduce interference
at m/z = 90 less than 0.01 cps and avoid interfering with
the 90Sr determination. Under the oxygen reaction modeof ICP-MS, a sensitivity of 100 cps/ppt for Sr is obtainedin this study. Instrumental LOD is 0.1 ppt (500 Bq/kg)
with 10 sec of integration time. After the developed
2 stage chemical separation procedure with 97 times

preconcentration for 90Sr, the method LOD is 5 Bq/
kg, which is enough low relative to the WHO Codex
guideline level (100 Bq/kg).
In 3 M HNO3, Ba was well retained in the resin. The
reason for this is that Ba tends to have a relatively highKd value in HNO3 solutions, behavior similar to that of
Sr. In 8 M HNO3, Ba was gradually eluted, although theresidual rate of Ba was 19%, which corresponded DF Ba of
2. Pb has also a higher Kd than Sr in HNO3 solutions23).
Because Pb is retained in the column, it was efficiently
removed (DFPb > 10000). In mass spectrometry, 140Ba and210
Pb does not interfere with 90Sr, but removal of such
radioisotopes is important in radiochemical analysis as it
is a naturally occurring beta emitter.
3.3 Application of the combined chromatography method
to real water samples
The combination of cation exchange chromatography
and Sr Resin chromatography can provide a 96-foldconcentration factor for Sr and DF Zr of 4.1×103 according
to experiment adopted to synthetic water samples.
Processing times for cation exchange resin and Sr Resinchromatography were 60 min and 120 min, respectively.
Sample throughput depends on laboratory equipment,
especially peristaltic pump availability for cationexchange. We used a 4-channel peristaltic pump andwe were able to process 4 batches in a day with a single
Sr Resin processing and ICP-MS determination, whichmeant 16 samples could be analyzed per day.
Ometakova and Dulanska26) reported that 89% of Sr
was recovered from a 50 mL water sample by carbonate
coprecipitation followed by separation with Sr Resin,which lost 11% of Sr. Combined method among phosphate
coprecipitation, TRU + Sr Resins, and ICP-MS/MS for
urine sample showed approximately 10 h of the processing
time (6.5 h for chemical separation and 3.5 h for ICP-MS/
MS measurement)13). The developed method is more rapid
and achieve quantitative Sr recovery. Maxwell et al.27)
reported rapid analytical method using Sr Resin andvacuum box system and gas flow proportional counter.
Rapidness of the procedure is comparable to that ofdeveloped method in this study. Radiation measurement
provides total activity of radioactive Sr (89Sr + 90Sr), andthen, 90Sr needs to be evaluated by 90 Y growth andseparation. Combination of the analysis of 90Sr by ICPMS
and 89Sr + 90Sr by radiation measurement can provide both89
Sr and 90Sr results in radiological incident situation.
The method was applied to real water samples (Table2): river water, tap water and two kinds of commerciallymarketed bottled water (BW). BW-1 was categorized asvery hard water (318 mg/L as CaCO3) and BW-2 was
soft water (36 mg/L as CaCO3). The concentration ofmajor components and trace elements including Zr were
determined by ICP-MS for the four sample types. Sr

Hirofumi Tazoe et al./ Radiation Environment and Medicine 2022 Vol.11, No.1 7–15

13

Table 2. Chemical composition of real water samples
Element
Na /ppm
Mg /ppm
K /ppmCa /ppm

River water
4.7
0.9
0.5
4.5

Tap water
8.1
1.9
0.8
6.1

BW-1
6.5
25.5
1.0
85.6

BW-2
10.0
5.0
1.3
6.2

Sr /ppb
Ba /ppb

25
3

24
8

342
110

58
3

Ge /ppt
Se /ppt
Rb /ppt
Zr /ppt
Cs /ppt

1
43
484
0.7
2

18
102
1122
<0.3
62

3
203
201
<0.3
1

12
52
4780
3.5
320

Table 3. Chemical yield and concentration factor (CF) for Sr, and decontamination factor (DF)for major components and possible interference elements
Yield
CF
DF
Na
Mg
K
Ca
Ge
Se
Rb
Zr
Cs
Ba
Repetition (N)River water
95.9% ± 2.3%
95.9 ± 2.3

Tap water
96.2% ± 2.5%
96.2 ± 2.5

BW-1
100.3% ± 1.2%
100.3 ± 1.2

BW-2
99.1% ± 2.9%
99.1 ± 2.9

130 ± 48
23 ± 1231 ± 192.6 ± 0.2
> 660
2,200 ± 1,100
37 ± 141,300 ± 325>250.070 ± 0.002
3290 ± 4545 ± 687 ± 10
3.7 ± 0.2
270 ± 240.0
1,500 ± 600
101 ± 52,850 ± 869
160 ± 810.064 ± 0.003
3240 ± 7216 ±591 ± 272.9 ± 0.3> 480
850 ± 311
62 ± 25563 ± 138
> 35
0.081 ± 0.003
3220 ± 6624 ±4
81 ± 26
1.5 ± 0.1
> 810
4,900 ± 2,20076 ± 26650 ± 135
63 ± 25
0.069 ± 0.003
3

concentration ranged from 24 ppb to 342 ppb (Table 2).
Zr, Se, and Ge concentrations were quite low for all
samples. Standard solutions for these elements wereadded to all samples to determine the DF precisely.
Concentrated HNO3 was added to four types of samples
to get 0.1 M HNO3 and the two-stage chemical separation
method was applied. The concentrations of Sr, and the
major and interference components were determined by
ICP-MS.
Sr chemical yield during cation exchange and Sr Resinchromatography ranged from 95.9% to 100.3%, which wereconsistent with our preciously described experiment usedsynthetic standard water samples (Table 3). Our results
also indicated that the major component causing water
hardness (~300 mg/L as CaCO3) did not interfere with the
Sr pre-concentration or recovery.
No difference was observed in the Ca chemicalyield ranging from 93% - 100% during cation exchange
chromatography. The method provided sufficientadsorption for Ca, Sr and Ba. Ion-exchange capacity of AG
50W-8 cation exchange resin is 1.7 meq/mL. Ca content

in 1 L of BW-1 was equivalent to 45 % of the total capacity(190 mg-Ca) for the 5 mL cation exchange resin. Higher
Ca concentrations and larger sample volumes mightsaturate the resin and reduce Sr recovery. Low DF for
Ba (0.06 - 0.08) was attributed to their affinity to Sr Resin.
As mentioned above, the level of Ca concentration for aseparated sample was sufficiently low ( < 30 ppm) for ICPMS.
DF f or Zr f or t he bot t led water samples wasapproximately 600, which was slightly lower than thosefor synthetic standard water samples and other water
samples. The major components in four types of water
samples seemed to enhance the Zr elution during cationexchange chromatography, although Zr concentration inriver water is generally low ( < 5 ppt) to avoid interferingwith 90Sr analysis during ICP-MS determination. If awater sample contains 10 ppb Zr, our two-stage chemical
separation method can reduce Zr concentration to 2 ppt(DF Zr = 500) and Zr interference with 90Sr can be eliminate
by using CRC-ICP-MS. DFs of Ge and Se were also
consistent with synthetic standard water samples, and the14

Hirofumi Tazoe et al./ Radiation Environment and Medicine 2022 Vol.11, No.1 7–15

contents were reduced to negligible levels.
As a result, we confirmed that this method for
determining 90Sr in water sample was also effective for
actual hard water samples with up to 300 mg/L as CaCO3of hard water.

References1.

Håkanson L, Sazykina T. A blind test of the MOIRA lake model
for radiocesium for Lake Uruskul, Russia, contaminated by
fallout from the Kyshtym accident in 1957. J Environ Radioact.
2001;54(3):327–44.

2.

Shagina NB, Vorobiova MI, Degteva MO, Peremyslova LM,
Shishkina EA, Anspaugh LR, et al. Reconstruction of thecontamination of the Techa River in 1949–1951 as a result of
releases from the “MAYAK” Production Association. Radiat
Environ Biophys. 2012;51(4):349–66.

3.

Monte L, Kryshev I, Sazykina T. Quantitative assessment of thelong term behaviour of 90Sr in Lake Uruskul, Southern Urals,
Russia. J Environ Radioact. 2002;62(1):61–74.

4.

Poston TM, Jaquish RE, Antonio EJ, Patton GW. Strontium-90 inalfalfa (Medicago sativa) around the Hanford Site in Southeastern
Washington State: An evaluation of surveillance data. J Environ
Radioact. 1998;39(1):87–105.

5.

Becker JS. Mass spectrometry of long-lived radionuclides.
Spectrochim Acta Part B At Spectrosc. 2003;58(10):1757–84.

6.

Warwick PE, Russell BC, Croudace IW, Zacharauskas Ž. Evaluationof inductively coupled plasma tandem mass spectrometry forradionuclide assay in nuclear waste characterisation. J Anal Atom
Spectrom. 2019;34(9):1810–21.

7.

Croudace IW, Russell B, Warwick PW. Plasma source mass
spectrometry for radioactive waste characterisation in supportof nuclear decommissioning: a review. J Anal Atom Spectrom.
2017;32(3):494–526.

8.

Bu W, Ni Y, Steinhauser G, Zheng W, Zheng J, Furuta N. The roleof mass spectrometry in radioactive contamination assessment
after the Fukushima nuclear accident. J Anal Atom Spectrom.
2018;33(4):519–46.

9.

Vonderheide AP, Zoriy MV, Izmer AV, Muller C, Pickhardt C,
Caruso J, et al. Determination of 90Sr at ultratrace levels in urine
by ICP-MS. J Anal Atom Spectrom. 2004;19(5):675–80.

10.

Zoriy MV, Ostapczuk P, Halicz L, Hille R, Becker JS. Determinationof 90Sr and Pu isotopes in contaminated groundwater samples
by inductively coupled plasma mass spectrometry. Int J Mass
Spectrom. 2005;242(2–3):203–9.

11.

Russell B, Garcia-Miranda M, Ivanov P. Development of an
optimised method for analysis of 90Sr in decommissioning
wastes by triple quadrupole inductively coupled plasma mass
spectrometry. Appl Radiat Isotop. 2017;126:35–9.

12.

Takagai Y, Furukawa M, Kameo Y, Suzuki K. Sequential
inductively coupled plasma quadrupole mass-spectrometricquantification of radioactive strontium-90 incorporating cascade
separation steps for radioactive contamination rapid survey. Anal
Methods. 2014;6(2):355–62.

13.

Tomita J, Takeuchi E. Rapid analytical method of 90Sr in urine
sample: Rapid separation of Sr by phosphate co-precipitation andextraction chromatography, followed by determination by triple
quadrupole inductively coupled plasma mass spectrometry (ICPMS/MS). Appl Radiat Isotop. 2019;150:103–9.

14.

Ohno T, Hirono M, Kakuta S, Sakata S. Determination ofstrontium 90 in environmental samples by triple quadrupole ICPMS and its application to Fukushima soil samples. J Anal Atom
Spectrom. 2018;33(6):1081–5.

15.

Stallard RF. River chemistry, geology, geomorphology and soils in
the Amazon and Orinoco Basins.: New York; 1985.

16.

Palmer MR, Edmond JM. Controls over the strontium isotope
composition of river water. Geochim Cosmochim Acta.
1992;56(5):2099–111.

17.

Vajda N, Kim C-K. Determination of radiostrontium isotopes:
A review of analytical methodology. Appl Radiat Isotop.

4. Conclusion
For 90Sr, which is an important target nuclide forenvironmental monitoring in the radiological incident, we
conducted research on speeding up and simplifying the90
Sr analysis method using in monitoring water quality.
To optimize the measurement with ICP-MS, we examined
the sample pretreatment conditions using chemical
separation by cation exchange resin and Sr Resin
extraction chromatography.
1. Sr was quantitatively recovered by cation exchange
resin chromatography from a 1 L synthetic water
sample, and anionic components such as Ge and Se
were efficiently removed. In addition, under the elution
condition to 3 M HNO3, it was possible to suppress theelution of Zr using a relatively small amount (30 mL) of
eluent.
2. The eluate from cation exchange resin chromatography
was used directly for subsequent solid-phase extraction
by Sr Resin, which further purified Sr enough for 90Sr
determination by ICP-MS.
3. Verification was performed on four types of actual
samples that included a sample of high hardness
bottled water. We confirmed that the results of thesynthetic standard water samples could be reproduced,
and that Sr was quantitatively recovered andinterfering elements were sufficiently removed.
4. 90Sr can be concentrated by a factor of 100 during thechemical separation without any evaporation step.
Processing time for 4 samples was 3 hours, which was
sufficiently fast for planning responses to radiologicalincident.
Acknowledgement
This work was further supported by Environmental
Radioactivity Research Network Center (E-21-09). In
addition, this work was partially supported by a Grant-inAid for Scientific Research on Innovative Areas (Researchin a proposed research area; ♯19H04245) from the Japan
Society for the Promotion of Science.
Conflict of Interest Disclosure
The authors declare that they have no conflict of interest.

Hirofumi Tazoe et al./ Radiation Environment and Medicine 2022 Vol.11, No.1 7–15

extraction of selected metal ions by a strontium selective
extraction chromatographic resin: Calculated vs experimental
curves. Solv Extract Ion Exch. 1992;10(2):337–61.

2010;68(12):2306–26.
18.

Shao Y, Yang G, Tazoe H, Ma L, Yamada M, Xu D. A review
of measurement methodologies and their applications toenvironmental 90Sr. J Environ Radioact. 2018;192:321–33.

19.

Chobola R, Chobola R, Mell P, Mell P, Daróczi L, Daróczi L, et al.
Rapid determination of radiostrontium isotopes in samples of NPP
origin. J Radioanal Nucl Chem. 2006;267(2):297–304.

20.

Tazoe H, Obata H, Tomita M, Namura S, Nishioka J, Yamagata
T, et al. Novel method for low level Sr-90 activity detection inseawater by combining oxalate precipitation and chelating resin
extraction. Geochem J. 2017;51(2):193–7.

21.

Dietz ML, Horwitz EP, Nelson DM, Wahlgren M. An improved
method for determining 89Sr and 90Sr in urine. Health phys.
1991;61(6):871–7.

22.

Kavasi N, Sahoo SK, Aono T. Zirconium decontamination factor
test on DGA and Sr resin for 90Sr analysis using inorganic mass
spectrometry. J Radioanal Nucl Chem. 2019;319(3):1339–44.

23.

Chiarizia R, Horwitz EP, Dietz ML. Acid dependency of the

15

24.

Horwitz EP, Dietz ML, Fisher DE. Separation and preconcentrationof strontium from biological, environmental, and nuclear waste
samples by extraction chromatography using a crown ether. Anal
Chem. 1991;63(5):522–5.

25.

Horwitz EP, Chiarizia R, Dietz ML. A novel strontium-selective
extraction chromatographic resin. Solv Extract Ion Exch.
1992;10(2):313–36.

26.

Ometáková J, Dulanská S, Mátel Lu, Remenec B. A comparison ofclassical 90Sr separation methods with selective separation using
molecular recognition technology products AnaLig® SR-01 gel, 3M
Empore™ strontium rad disk and extraction chromatography Sr®
resin. J Radioanal Nucl Chem. 2011;290(2):319–23.

27.

Maxwell SL, Culligan BK. Rapid separation method for emergency
water and urine samples. J Radioanal Nucl Chem. 2009;279(3):901–7.