Isolation of radioactive strontium from natural samples: A semi-automatic procedure

A procedure for semi-automatic isolation and determination of radioactive strontium from natural samples was developed. The method was tested by the determination of⁹⁰Sr in soil samples and the results obtained were compared to those obtained by the standard procedure. The procedure consists of leaching of strontium (and other cations as well) from soil samples with a water suspension of the cation exchanger Amberlite IR-20, the separation of strontium from other cations, e.g., potassium, calcium, sodium, barium by the anion exchangers Amberlite CG-400 or Dowex Ag 1×8 with 0.25M HNO₃ in ethanol-methanol mixture as eluent in the apparatus specially constructed for this purpose. Determination of⁹⁰Sr was done on the low-level gas-flow β-counter and by Cherenkow counting on the liquid-scintillation counter few hours after the separation. It was shown that this procedure might be successfully applied for rapid determination of⁹⁰Sr in soil samples and other natural samples in a timesaving manner.     

Separation of radioactive strontium from natural samples by means of mixed-solvent anion exchange

A new procedure for isolation and determination of⁹⁰Sr in real natural samples is presented. It consists of bringing natural samples in a soluble form suitable for separation on an ion-exchange column, separation of calcium from strontium by means of the anion exchanger Amberlite CG-400 and 0.25M HNO₃ in methanol as eluent for calcium, and the determination of⁹⁰Sr using a low level -counter after elution with H₂O, scavenging steps and SrCO₃ precipitation. The method was tested with IAEA standards of natural samples with known contents of⁹⁰Sr, and water samples, where the concentration of⁹⁰Sr was previously determined by the standard IAEA procedure. The results obtained show that it is possible to isolate and determine low levels of⁹⁰Sr in natural samples. The procedure is favorable because of the simple separation of radioaactive strontium without using fuming nitric acid.     

Bestimmung des Gehaltes an90Sr und89Sr in Proben tierischer und pflanzlicher Herkunft

A method is described for the determination of⁸⁹Sr and⁹⁰Sr in samples of plant and animal origin. The Rehak-Feddersen method was modified to measure⁹⁰Sr. Modification was made in the sample preparation and in the toluene-HDEHP [di(2-ethylhexyl)phosphoric acid] extraction. After the extraction of yttrium, strontium is separated with nitric acid and—calculating with a correction factor—⁸⁹Sr can directly be determined. Namely,⁸⁹Sr can be measured in an aqueous solution by a liquid scintillation technique with an efficiency of 30% while⁹⁰Sr with 1.4% only. Quenching of the solution—depending on the composition—which may influence the measurement of⁹⁰Y and⁸⁹Sr was also examined. Detection limits and reproducibilities are given. Finally, evaluation of the experimental data is reported.      

Rapid determination of 89,90Sr in wide range of activity concentration by combination of yttrium, strontium separation and Cherenkov counting

The methodology for the rapid determination of ^89,90Sr in wide range of activity concentration is given. Methodology is based on simultaneous separation of strontium and yttrium from samples by mixed solvent anion exchange chromatography, mutual separation of ^89,90Sr from ⁹⁰Y by hydroxide precipitation and quantitative ^89,90Sr determination by Cherenkov counting within 3 days. It is shown that Y and Sr can be efficiently separated from alkaline, alkaline earth and transition elements as well as from lanthanides and actinides on the column filed by strong base anion exchanger in nitrate form and 0.25 M HNO₃ in mixture of ethanol and methanol as eluent. Decontamination factor for Ba, La and other examined elements except calcium is low and can not affect quantitative determination in predictable circumstances. Methodology for quantitative determination by Cherenkov counting based on following the changes of sample activity over time is described and discussed. It has been shown that ^89,90Sr can be determined with acceptable accuracy when ⁸⁹Sr/⁹⁰Sr ratio is over 10:1 and that separation of Y enables reliable determination of ⁸⁹Sr and ⁹⁰Sr in wide range of ⁸⁹Sr/⁹⁰Sr ratios (60:1) and in some cases in presence of other yttrium and strontium isotopes. The methodology was tested by determination of ^89,90Sr in Analytics crosscheck samples (nuclear waste sample) and ERA proficiency testing samples (low level activity samples). Obtained results shows that by using of low level liquid scintillation counter it can be possible to determine ⁸⁹Sr and ⁹⁰Sr in wide range of concentration activity (1–1,000 Bq/L/kg) with uncertainty below 10% within 2–3 days. Results also show that accuracy of determination of ⁸⁹Sr (and ⁹⁰Sr) strongly depends on the determination of difference between separation and counting time when activity ratio of ⁸⁹Sr/⁹⁰Sr is high. Examination the influence of media and vial type on background radiation and counting efficiency has shown that lowest limit of determination can be obtained by using of HNO₃ in plastic vials as counting media, because in this combination figure of merit is maximized. For the recovery of 50% and 100 min of counting time estimated MDA is 55 Bq and 90 Bq for ⁹⁰Sr and ⁸⁹Sr, respectively. Analysis of combined uncertainty shows that it mainly depends on uncertainty of efficiency and recovery determination, uncertainty of activities determination for both isotopes and level of background radiation.     

Determination of radioactive strontium in seawater

This paper describes the procedures of isolating strontium and yttrium from seawater that enable the determination of ^89,90Sr. In one procedure, strontium is directly isolated from seawater on the column filled with Sr resin by binding of strontium to the resin from 3 M HNO₃ in a seawater, and successive elution with HNO₃. In others, strontium is precipitated from seawater with (NH₄)₂CO₃, followed by isolation on a Sr column or an anion exchange column. It is shown that strontium precipitation is optimal with concentration of 0.3 M (NH₄)₂CO₃ at pH = 11. In these conditions, 100% Y, 78% Sr, 80% Ca and 50% Mg are precipitated. Strontium is bound on to Sr column from 5 to 8 M HNO₃, separated from other elements by elution with 3 M HNO₃ and 0.05 M HNO₃. Strontium and yttrium are bound on to anion exchange column from alcoholic solutions of nitric acid. The optimum mixture of alcohols for sample binding is a mixture of ethanol and methanol with the volume ratio 1:3. Strontium and yttrium are separated from Mg, Ca, K, and other elements by elution with 0.25 M HNO₃ in the mixture of ethanol and methanol. After the separation, yttrium and strontium are eluted from the column with water or methanol.In the procedure of direct isolation from 1 l of the sample, the average recovery of 50% was obtained. In the remaining two procedures, the strontium recovery was about 60% for the Sr column and 65% for anion exchange column. Recovery of yttrium is about 70% for the anion exchange column. It turned out that the procedure with the Sr resin (direct isolation and isolation after precipitation) is simpler and faster in the phase of the isolation on the column in comparison with the procedure with the anion exchanger. The procedure with the anion exchanger, however, enables the simultaneous isolation of yttrium and strontium and rapid determination of ^89,90Sr. These procedures were tested by determination of ^89,90Sr on liquid scintillation counter and Cherenkov counting in 5 M HNO₃. Obtained results showed that activity of 50 mBq l⁻¹ of ^89,90Sr and higher can be simultaneously determined.     

Determination of90Sr by thin layer radiochromatography

A simple method for the determination of⁹⁰Sr by using thin layer chromatography on silica gel or cellulose pretreated with calcium oxalate is proposed. In these conditions a complete separation between strontium and its daughter yttrium is obtained. Radioactivity of separated elements was measured by a linear multiscanner analyzer and the results were computer processed to obtain the activity of⁹⁰Sr. The method has been applied to samples of water and milk subjected to a very simple extraction procedure. Under the experimental conditions used, the detection limit is about 25 mBq of deposited radioactivity, which corresponds to about 6 Bq/l.     

The solvent extraction of carrier-free90Y from90Sr with crown ethers

A simple solvent extraction method has been developed for the separation of⁹⁰Y from⁹⁰Sr. Crown ether dissolved in chloroform was used as a selective reagent and organic picrate anion was chosen as a counter ion. The effect of various factors on the extraction separation of strontium and yttrium in the system have been studied. The extraction equilibrium constant of strontium logK _ex=9.15 was obtained from the study of the distribution coefficient versus the crown ether concentration. The separation method was simple, resulted high purity (>99.9%) and quantitative yield, and took less than half an hour.     

A rapid method for the determination of radiostrontium in river water

A rapid analytical method, applicable for the selective separation and determination of⁹⁰Sr and⁸⁹Sr in river water, is described. Strontium is extracted from the water sample at pH 10.5 by TTA/TOPO in cyclohexane in the presence of Tiron as masking agent for interfering ß-emitters. Radiostrontium is measured by liquid scintillation after back-extraction into 1N nitric acid. The distribution coefficient of strontium is over 400 and the separation factors from other radionuclides are higher than 5.0×10³.     

The simple radiochemical determination of 90Sr in environmental solid samples by solvent extraction

Determination of ⁹⁰Sr in environmental solid samples is a challenging task because of the presence of so many other radionuclides in samples of interest. This problem was dealt with by radiochemical separation of strontium followed by yttrium separation and Cerenkov counting of the high-energy ??-particle emissions of ⁹⁰Y in order to quantitate ⁹⁰Sr. In this work, an improved method is described for the determination of ⁹⁰Sr in soil samples, through the separation of the daughter ⁹⁰Y at equilibrium. The procedure is based on the HDEHP solvent extraction in combination with liquid scintillation spectrometry (LSS). A low background Quantulus has been optimized for low level counting of Cerenkov radiation emitted by the hard ??-emitter ⁹⁰Y. The analytical quality of the method has been checked by analyzing IAEA Soil-375 reference materials. The analytical method has also been successfully applied to the determination of ⁹⁰Sr for moss-soil samples in inter-laboratory exercises through IAEA??s ALMERA network. The chemical recovery for ⁹⁰Y extraction ranged from 80 to 85% and the counting efficiency was 73% in the window 25?C400 keV.     

Studies on soil samples mineralization conditions preceding the determination of 90Sr

Some results of the extraction of strontium and yttrium from soil samples by concentrated nitric acid are described. The concentration of Sr and Y in the solid was determined by XRF method. The results obtained allowed to elaborate the conditions of acid leaching and to propose an analytical procedure for the determination of ⁹⁰Sr in samples without their total dissolution.     

Preparation of animal tissue samples for the determination of90Sr and actinides

A unique procedure permitting the determination of⁹⁰Sr and actinides in the same protion of sample, with good chemical yields of all analytes, is presented. Animal tissue samples containing bone are ashed, spiked with^{2 3 2}U,^{2 4 2}Pu,^{2 4 3}Am and^{8 5}Sr and solubilized. The actinides and strontium are gathered and separated by a series of coprecipitations with, cerium hydroxide and cerium fluoride. Actinide separation and determination and purification and determination of⁹⁰Sr are accomplished by a combination of several well-known procedures. The laboratory method consistently results in high chemical yields of all the analytes and overcomes interferences from phosphates and calcium.     

Methodology for determination of 89Sr and 90Sr in radiological emergency: I. Scenario dependent evaluation of potentially interfering radionuclides

Early determination of ⁸⁹Sr and ⁹⁰Sr in radiological emergency is hampered by the presence of interfering short-lived fission products. In this study, three commonly used radioanalytical strategies for ⁸⁹Sr and ⁹⁰Sr were evaluated theoretically considering their suitability in a nuclear explosion scenario. The methods were evaluated with respect to the need for decay time of interfering short-lived strontium and yttrium isotopes, and reduction of other known interfering nuclides prior to measurement. The strategy shown to be most successful included initial separation of strontium and determination of ⁸⁹Sr, followed by an yttrium separation and counting of ⁹⁰Y. ⁸⁹Sr and ⁹⁰Sr could be determined about 5 and 9 days after a nuclear explosion, respectively.     

Isolation of lead from water samples and determination of Pb

This paper describes the procedures of isolating lead and strontium from the larger volume of seawater and drinking water samples that enable the determination of ²¹⁰Pb on gamma spectrometer and ^89,90Sr on liquid scintillation counter. In one procedure, lead is directly isolated from water sample on the column filled with Sr resin by binding of lead on the Sr resin column from 0.2 M HCl in water sample, and successive elution with 0.2 and 8 M HCl. In others, lead and strontium are precipitated from sample with (NH₄)₂CO₃, followed by isolation on an anion exchange column. Lead, strontium and yttrium are bound onto anion exchange column (filled with Amberlite CG-400 in nitrate form) from alcoholic solutions of nitric acid. Lead, Sr and Y are separated from Mg, Ca, K, and other elements by elution with 0.25 M HNO₃ in the mixture of ethanol and methanol. After that, strontium and yttrium are separated from lead by elution with 0.25 M HNO₃ in the mixture of ethanol and water.

The procedure with the Sr resin (direct isolation) is simpler and faster in the phase of isolation on the column in comparison with the procedure with the anion exchanger. The procedure with the anion exchanger, however, makes possible the simultaneous isolation of lead, yttrium and strontium and rapid determination of ^89,90Sr. These procedures were tested by determination of ²¹⁰Pb and ^89,90Sr in real sample. Obtained results showed that Pb can be efficiently isolated (with high recovery) from sample and activity of 6 mBq l⁻¹ of ²¹⁰Pb and higher can be determined.     

Artificial radioactive contamination of sediment samples along the Romanian sector of the Danube river and the Black Sea coast

The concentrations of¹³⁷Cs were determined by in 11 sediment samples, collected along the Romanian sector of the Danube river and the Black Sea coast during 1994 γ-ray spectrometry. The concentrations of⁹⁰Sr in the same sediment samples were determined by β-counting of the⁹⁰Y oxalate, precipitated after strontium separation using a strontium extraction chromatography column. The concentration distributions of¹³⁷Cs and⁹⁰Sr are compared with the²³⁸Pu and^239,240Pu concentration distributions in the same samples, reported in a previous paper. The accumulation potential of¹³⁷Cs,⁹⁰Sr and plutonium isotopes in the river and sea sediments analysed is discussed.     

New method for90Sr determination in liquid samples

A method has been developed for measuring⁹⁰Sr activity in liquid samples. After concentrating strontium from the sample by coprecipitation with calcium phosphate, the residue is dissolved in 8N HNO₃ and passed through an extraction chromatographic column (Sr.Spec) containing a new material that selectively retains strontium. This is eluted from the column with 0.05N HNO₃ and counted by liquid scintillation. Measurement is performed using a double window method, that allows a rapid and single determination of⁹⁰Sr.     

Determination of strontium radioisotopes in soils

Summary A method is proposed for determination of radiostrontium in soils which is based on selective strontium separation by liquid-liquid extraction with dicyclohexano-18-crown-6 in chloroform, loading of the extract on a thin-layer plate and TLC separation of strontium and yttrium radioisotopes using a circular procedure. The method allows the separate determination of ⁸⁹Sr and ⁹⁰Sr. The strontium chemical yield is more than 90%, the detection limit is about 0.5 Bk/g, RSD is equal to 2–5%.     

Improvements to arapid method for separating strontium from liquid milk by treatment with a chelating resin and crown ethers

In an attempt to improve on a previously reported method¹ for rapidly isolating Sr from liquid milk, the following investigations have been carried out: (1) elution of strontium from a chelating resin with dilute nitric acid, (2) separation of strontium from calcium by extracting from this eluate into chloroform solutions of dicyclohexyl-18-crown-6 (DC18C6), (3) transfer of the strontium into aqueous solution, and (4) removal of barium from this solution by extracting into dichloromethane solutions of 21-crown-7 (21C7). Based on the findings of these studies, a separation scheme was proposed and tested by participating in an interlaboratory comparison on the analysis of⁸⁹Sr and⁹⁰Sr in skimmed milk. The separation scheme requires about 3 hours, provides strontium recoveries greater than 90%, and ensures adequate decontamination factors for the nuclides that occur in milk.     

Separation of Sr in combination of ion exchange and Sr resin with alcohol-nitric acid solution and rapid determination of <Superscript>90</Superscript>Sr in wine and soil samples

This paper describes the procedures of isolating strontium from wine and soil samples which enable creating of procedure for rapid determination of ⁹⁰Sr. The method of determination of ⁹⁰Sr includes binding of Sr on the cationic exchanger IR-120 from the sample and simultaneous elution from the cation column and binding on the Sr column, separation of Sr on Sr resin with HNO₃ even in presence of alcohols and subsequent Cherenkov counting. Sr can be efficiently bind on Sr resin and separated from the other elements with lower acid concentrations in the presence of a low portion of alcohol, or even from a wine sample without the loss of Sr resin capacity. The binding strength of Sr on Sr resin decreases with the rising of HNO₃ concentration (1–5 M) in the presence of 13% of ethanol or methanol, and with the rising of the alcohol portion in constant concentration of HNO₃. Application of cation exchanger for Sr binding in phase of sample preparation decreases Sr column loading and improve Sr recovery. The method allows the determination of ⁹⁰Sr activities in wine and soil sample lower than 10 mBq in reasonable time.     

Selective separation of yttrium(III) through a liquid membrane system using 2-thenoyltrifluoroacetone as an extractant carrier

2-Thenoyltrifluoroacetone has been offered as a mobile carrier in organic phase for the transport and selective separation of yttrium from aqueous media using a liquid membrane system. Perceivably, the use of n-propylamine (PA) in the source phase enhances the transport of yttrium ions. The extraction and stripping conditions have entirely been evaluated and explained. The suggested method has been utilized for the separation of yttrium(III) from its binary mixtures with strontium(II) and some other cations such as Ni²⁺, Co²⁺, Ag⁺, Fe²⁺, Al³⁺, Cu²⁺, Hg²⁺and Cs⁺ in aqueous solutions of pH 5.4 in the presence of PA, while 1 M nitric acid was acting as a stripping agent in the receiving division. Cyanide ion and 5-sulfosalicylic acid have been used as masking agents to minimize the interferences from different transition metal ions and Al³⁺ in the source phase, respectively. ⁹⁰Y in secular equilibrium with ⁹⁰Sr in the source phase, was transferred to receiving phase and separated completely from its long-lived parent isotope. The activity of the transported ⁹⁰Y was found to decay with a half-life 64.17 ± 0.05 h. The purity of yttrium-90 was comparable or better than the other applied liquid membrane systems for purification of yttrium-90.     

Bestimmung von90Sr auf der Ionex-Säule in Milch und Knochen Unter Berücksichtigung der Komplexen Eigenschaften Einiger Reagenzien

The determination of⁹⁰Sr is extremely difficult in biological materials by chemical meth ods owing to the quantity of calcium associated. The problem consists of the quantitative removal of calcium and of the selective extraction of⁹⁰Sr using strontium carrier. It can be solved by precipitation and extraction methods, or by ion exchange chromatography. Following our previous works, experimental evidence is presented using ion exchange technique for these purposees, where complex compounds are used as eluents for calcium removal. For the determination of⁹⁰Sr in milk and bones, calcium was removed with 1,2-diamino-cyclohexane-N,N,N′,N′-tetraacetic acid (CyDTA) eluent from Amberlite IR-120 column. Our results show that compounds of chelatone type used as eluents with a strong acidic cation exchanger column are the most convenient, for they prefer to compound with ligands of weaker or mean complexibility (hydrochloric acid, citric acid and lactic acid).