Rapid Strontium-90 Water Analysis Using the Empore™ Strontium Rad Disk
- 7 days ago
- 9 min read
Authors: Jianwen Hu, Xiaohui Zhang, Guotao Lu
Study summary: A rapid solid-phase extraction (SPE) method for Strontium-90 water analysis has been validated using the Empore™ Strontium Rad Disk and a low-background α/β counter. After acidifying a 1.00 L water sample and passing it through the 47 mm Strontium SPE disk, the disk is counted directly for 60 minutes with no additional sample preparation. The method achieves a minimum detectable concentration of 0.019 Bq/L with a total detection efficiency of 42.1%, and completes the entire workflow in approximately 2 hours — compared to 2–3 days for traditional extraction chromatography. Validation against samples with known 90Sr activity gave relative deviations below 10%, confirming the method's suitability for emergency response, drinking water screening, and routine radiation monitoring.
TL;DR: Traditional Strontium-90 water analysis takes 2–3 days of complex radiochemical separation per sample — too slow for nuclear emergencies, drinking water screening, or operational decision-making. The Empore™ Strontium Rad Disk reduces the entire workflow to ~2 hours: acidify the 1 L sample, pass it through the 47 mm SPE disk, and count the disk directly in a low-background α/β counter. MDC is 0.019 Bq/L with 42.1% total detection efficiency, and validation against known-activity samples yielded relative deviations of 4.8% and 5.5%.
Study at a Glance
Introduction: The Need for Rapid 90Sr Analysis
90Strontium (90Sr) is an artificial pure β-emitting radionuclide. It has a maximum β decay energy of 545.9 keV and a half-life of 28.8 years. 90Sr is one of the radionuclides that requires close monitoring in natural water — both as a routine environmental control and in response to nuclear incidents.
At present, many laboratories use extraction chromatography to analyze 90Sr in water samples, but this method is cumbersome to operate and has a long analysis period. It takes an average of 2–3 days for each water sample. This timeframe is not conducive to the rapid determination of 90Sr in water samples in emergency situations, where decision-makers need actionable data in hours, not days.
Why turnaround time matters for 90Sr: In a nuclear incident, drinking water contamination event, or routine site monitoring around nuclear facilities, a 2–3 day analytical delay can mean prolonged exposure, delayed protective actions, and operational uncertainty. A 2-hour method enables same-shift, same-day decisions.
The Empore™ Strontium SPE disk is made of a strontium-specific sorbent embedded in a polytetrafluoroethylene (PTFE) fiber web, forming a thin 47 mm disk. This thin-disk geometry enables a critical workflow simplification: after the water sample passes through the disk, the disk itself can be placed directly into a low-background α/β counter for measurement — with no further elution, evaporation, or radiochemical separation required.
Compared to traditional analytical methods for 90Sr in water, the Empore disk procedure is simpler, has shorter detection time, and provides a stable chemical recovery rate. It is suitable for the rapid determination of 90Sr in water samples for a range of applications, from emergency response screening to routine drinking water and environmental monitoring.
Headline performance:
Total workflow: ~2 hours (vs. 2–3 days for extraction chromatography)
Minimum detectable concentration (MDC): 0.019 Bq/L
Total detection efficiency: 42.1%
Validation deviation vs. known-activity samples: < 10% (4.8% and 5.5%)
Disk format: 47 mm — fits directly into standard low-background α/β counters
Why the Empore™ Strontium Rad Disk
Conventional 90Sr radiochemical analysis is multi-step: precipitation, ion-exchange separation, repeated digestion, and finally Cherenkov counting or liquid scintillation of the purified strontium fraction. Each step adds time, sample handling complexity, and opportunity for contamination. The Empore™ Strontium Rad Disk consolidates the strontium isolation, concentration, and counting-source preparation steps into a single membrane:
Strontium-selective chemistry built into the disk — the strontium-specific sorbent is embedded directly in the PTFE fiber web, eliminating loose-particle handling and packing inconsistencies
Direct disk-to-counter workflow — the 47 mm disk format is dimensionally compatible with low-background α/β counters, so the disk is counted directly with no eluate transfer or evaporation step
Stable chemical recovery rate — the disk's uniform sorbent loading produces reproducible recovery across samples, allowing the product of recovery and instrument efficiency to be used as the total detection efficiency in routine quantitation
Compatible with strong nitric acid loading — the PTFE matrix tolerates the 65% / 2 mol/L HNO₃ matrices used in this method without degradation
Suited to emergency-response timelines — entire workflow completes in approximately 2 hours, enabling same-day decision-making
Reagents & Instruments
Reagents
90Sr standard solution — 87.0 Bq/g (used for total detection efficiency calibration)
Strontium carrier solution — 2.00 mg-Sr/mL
Nitric acid — analytically pure (used at 65% concentration for sample acidification, and at 2 mol/L for disk pre-rinse and post-rinse)
Deionized water — for final disk rinse
SPE Media
Empore™ Strontium SPE disk, 47 mm — SKU: 98-0405-0064-1 (CDS Analytical, Oxford, PA, USA)
Counting Instrument
MPC-9604 low-background α/β counter (ORTEC, USA) — used for direct measurement of 90Sr on the SPE disk
Validated Procedure for Strontium-90 Water Analysis
1. Sample Acidification
Take a 1.00 L water sample. Add 150 mL of 65% nitric acid solution and 1.00 mL of 2.00 mg/mL strontium carrier solution. Stir the mixture for 10 minutes.
2. SPE Loading
Pass the following solutions through the Empore™ Strontium SPE disk in series at a flow rate of 80 mL/min:
50 mL of 2 mol/L nitric acid solution (pre-rinse)
The acidified 1.00 L sample solution
200 mL of 2 mol/L nitric acid solution (post-rinse to remove interferents)
50 mL of deionized water (final rinse)
The effluent is discarded — the 90Sr is retained on the disk.
3. Direct Counting
Remove the Strontium SPE disk from the filtration apparatus and place it directly into the low-background α/β counter. Measure for 60 minutes.
⚠ Critical workflow note: The Empore disk is counted directly — no elution, evaporation, or source-mounting step is performed. This direct disk-to-counter step is what enables the 2-hour total workflow time, and is the main reason the Empore method is faster than traditional radiochemical separation procedures.
Calculation of Activity Concentration
Formula 1 — 90Sr Activity Concentration
The activity concentration of 90Sr in the water sample is calculated according to Formula (1):
Total Detection Efficiency (E) Calibration
To determine the total detection efficiency E, take 1.00 g of the 90Sr standard solution (87.0 Bq/g, with known activity), add it into 1.00 L of deionized water, and process the spiked solution exactly as described in the validated procedure above. Calculate the total detection efficiency from the resulting count rate and known activity.
Under typical conditions in this work, the total detection efficiency was determined to be E = 42.1%. This value combines the chemical recovery of strontium on the SPE disk and the geometric/counting efficiency of the α/β counter into a single calibration constant.
Minimum Detectable Concentration (MDC)
The minimum detectable concentration of this method is calculated according to Formula (2):
Substituting typical experimental conditions:
The 0.019 Bq/L MDC is achieved with a 1.00 L sample volume and 60-minute counting time — an operationally practical configuration that fits within a 2-hour total turnaround.
Real Sample Validation
After verifying the method's performance characteristics, two groups of water samples (Sample A and Sample B) with known standard 90Sr activity values were analyzed as a laboratory comparison. Results are shown in Table 1.
Table 1 — Sample Measurement Results
Validation outcome: Both relative deviations are under 10% versus the known standard values, confirming the method is suitable for the analysis of 90Sr in water samples in emergency situations.
Where This Method Fits
The 2-hour turnaround, 0.019 Bq/L sensitivity, and direct disk-to-counter workflow make the Empore™ Strontium Rad Disk method applicable across several radiation monitoring scenarios:
Nuclear emergency response — accident screening, rapid characterization of contaminated water near affected sites, and supporting protective-action decision-making within operational timeframes
Drinking water safety verification — rapid screening of municipal water sources, well water, and emergency drinking water supplies when 90Sr contamination is a concern
Environmental monitoring around nuclear facilities — routine surveillance of water bodies adjacent to nuclear power plants, fuel cycle facilities, and radioactive waste storage sites
Legacy contaminated site investigation — characterization of groundwater and surface water at historical nuclear installations and weapons production legacy sites where 90Sr is among the contaminants of concern
Radioactive waste characterization — verification analysis on aqueous waste streams prior to treatment or release
Conclusion
A rapid analysis method for 90Sr in water under emergency conditions has been established using the Empore™ Strontium Rad Disk (47 mm, SKU 98-0405-0064-1) and a low-background α/β counter. After a 1.00 L water sample is acidified and passed through the Strontium SPE disk, the 90Sr retained on the disk is measured directly with the counter — no elution or source preparation step is required.
The method offers:
A stable chemical recovery rate — the product of the recovery rate and the instrument detection efficiency can be used as the total detection efficiency
A minimum detectable concentration (MDC) of 0.019 Bq/L under typical conditions
A total detection efficiency of 42.1%
A complete workflow time of approximately 2 hours, compared to 2–3 days for traditional extraction chromatography
Validation against known-activity samples with relative deviations of 4.8% and 5.5% (both under 10%)
This method realizes the rapid analysis of 90Sr in water under emergency conditions, and has good application potential for nuclear emergency response, drinking water safety screening, environmental radiation monitoring, and characterization of legacy contaminated sites.
Frequently Asked Questions
What is strontium-90 and why is it monitored in water?
90Strontium is an artificial pure β-emitting radionuclide with a maximum β decay energy of 545.9 keV and a half-life of 28.8 years. It is one of the radionuclides that requires monitoring in natural water sources because of its long half-life, biological similarity to calcium (which causes accumulation in bone tissue), and historical release from atmospheric nuclear weapons testing, nuclear power operations, and nuclear accidents such as Chernobyl and Fukushima.
How fast is the Empore Strontium Rad Disk method compared to traditional methods?
The Empore Strontium SPE Disk method completes 90Sr analysis in approximately 2 hours total processing time per water sample. Traditional extraction chromatography methods used in many laboratories require an average of 2–3 days per sample. This makes the Empore disk method especially suitable for emergency response situations, accident scenarios, and time-critical environmental monitoring where conventional radiochemical separation is too slow.
What is the minimum detectable concentration (MDC) of this 90Sr method?
The MDC of this method is 0.019 Bq/L under typical conditions. The MDC was calculated using a 1.00 L sample volume, 60-minute background measurement time, background count rate of 0.65 cpm, and total detection efficiency of 42.1%. This sensitivity is suitable for both regulatory environmental monitoring and emergency response screening.
What instrument is used to measure the 90Sr on the Empore disk?
After the water sample passes through the Empore Strontium SPE disk, the disk is placed directly into a low-background α/β counter for measurement. The validation data in this application note was generated using an MPC-9604 low-background α/β counter (ORTEC, USA). The 47 mm disk format is compatible with standard low-background counters; the 90Sr adsorbed on the disk is measured directly without further sample preparation.
What is the detection efficiency of this 90Sr method?
The total detection efficiency (E) is 42.1% under the validated conditions, calculated using the Formula 2 method with a known-activity 90Sr standard solution. The total detection efficiency reflects both the chemical recovery of strontium on the SPE disk and the geometric/counting efficiency of the α/β counter. This combined efficiency is used directly in the activity concentration formula for sample quantitation.
How is sample acidity controlled in this 90Sr SPE method?
Sample acidity is controlled by adding 150 mL of 65% nitric acid solution to each 1.00 L water sample, along with 1.00 mL of 2.00 mg/mL strontium carrier solution, followed by stirring for 10 minutes. The disk is then conditioned and the sample is loaded in series with 50 mL of 2 mol/L HNO₃ (pre-rinse), the sample, 200 mL of 2 mol/L HNO₃ (post-rinse), and 50 mL of deionized water — all at a flow rate of 80 mL/min through the Empore Strontium SPE disk.
What is the typical use case for the Empore Strontium Rad Disk method?
The method is suitable for rapid 90Sr determination in water for a range of applications: nuclear emergency response, drinking water safety verification, environmental monitoring around nuclear power facilities and waste storage sites, and verification analysis for legacy contaminated sites. The 2-hour turnaround makes it especially valuable wherever conventional 2–3 day radiochemical separation is too slow for operational decision-making.
How was the method validated?
The method was validated by analyzing two groups of water samples (Sample A and Sample B) as a laboratory comparison against samples with known standard 90Sr activity values. Sample A was measured at 27.36 Bq/L vs. a standard value of 24.84 Bq/L (4.8% relative deviation); Sample B was measured at 7.42 Bq/L vs. a standard value of 8.29 Bq/L (5.5% relative deviation). Both relative deviations were under 10%, demonstrating the method is suitable for 90Sr analysis in water samples in emergency situations.
References
Zhang Z., Ninomiya K., Takahashi N., Saito T., Kita K., Yamaguchi Y., Shinohara A. Rapid isolation method for radioactive strontium using Empore™ Strontium Rad Disk. Journal of Nuclear and Radiochemical Sciences, 2016, 16(0).
Smith L. L., Orlandini K. A., Alvarado J. S., Hoffmann K. M., Seely D. C., Shannon R. T. Application of Empore™ Strontium Rad Disks to the Analysis of Radio-strontium in Environmental Water Samples. Radiochimica Acta, 2013, 73(3).
Heynen F., Minne E., Hallez S. Empore™ strontium rad disks validation procedure for strontium-90 analysis in radioactive wastes. Radiochimica Acta International Journal for Chemical Aspects of Nuclear Science and Technology, 2007, 95(9).
Hu J., Zhang X., Lu G. CDS Analytical Application Note #276: Rapid Determination of 90Strontium in Water Using Empore™ Strontium Disk. CDS Analytical, LLC.
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