Radiochemical determination of210Po and210Pb in water

A method for²¹⁰Po and²¹⁰Pb determination in water samples is described. The nuclides are concentrated, in presence of added²⁰⁸Po and lead carrier, by evaporation. Then the polonium is plated electroless from the acidic solution on a copper planchet and measured by alpha spectrometry.²¹⁰Pb separation from the other isotopes is based on the solutility of PbSO₄ in citrate.²¹⁰Pb content is determined by measuring the activity of its daughter²¹⁰Bi. The critical steps in the isolation of lead have been examined and discussed.     

Determination of (210)Pb, (210)Bi and (210)Po in natural waters and other materials by electrochemical separation

An improved method for determination of (210)Pb, (210)Bi and (210)Po in both natural waters and solid materials has been developed. Polonium-210 is spontaneously plated onto a silver disc from dilute hydrochloric acid medium. Bismuth-210 is then electro-deposited onto a platinum gauze cathode directly from the same solution, with a graphite rod as anode. Finally, (210)Pb is electro-deposited from a fluoroborate medium onto the same platinum gauze, used as the anode. All three nuclides are subsequently measured by standard low-level alpha and beta counting techniques. The speed of this method (approximately 6 hr per sample after pretreatment) is a distinct advantage over existing techniques, as (210)Bi must be quickly separated from (210)Pb because of its 5.02-day half-life. Another advantage of this method is that the chemical form of the sample solution is suitable for use of established separation schemes for determining other decay-series isotopes (U, Th, Pa, etc.) after the three short-lived nuclides have been processed.     

Sequential and rapid determination of Po-210, Bi-210 and Pb-210 in natural waters

A sequential and rapid separation method for the determination of radon daughter nuclides, Pb-210, Bi-210 and Po-210 has been developed for application to natural waters. Rapid separation is attained by the use of the same hydrochloric acid solution. After isolation of the three radionuclides from the sample by co-precipitation with added Fe³⁺, polonium isotopes are first spontaneously deposited onto a silver disc from a 0.5N hydrochloric acid solution. Next, bismuth isotopes are electrodeposited onto a platinum net cathode coupled with a platinum coil anode at 1.2 V. Finally, lead isotopes are electrodeposited onto a platinum net cathode at 1.8 V from the remaining solution by adding hydroxylamine hydrochloride as an anodic depolarizer. This method can be applied to meteorological precipitation samples where these three nuclides are separated within 10 hr after the sampling with chemical yields of more than 80% for Po-210 and Bi-210 and more than 70% for Pb-210. This method is applicable to other environmental water samples.     

Evaluation of measurement uncertainty in the determination of 210Pb and 210Po using beta counting and alpha spectrometry

 Measurement uncertainties in the determination of ²¹⁰Pb and ²¹⁰Po in Reference Material IAEA-300 (Baltic Sea Sediment) were evaluated. ²¹⁰Pb and ²¹⁰Po were separated from the matrix using an Sr resin column. The chemical yield of ²¹⁰Pb was determined gravimetrically in PbSO₄ form. Precipitation was followed by beta proportional counting after ²¹⁰Bi ingrowth. ²¹⁰Po was determined by alpha spectrometry after its spontaneous deposition on a Cu planchet. The major source of uncertainty was identified as the statistical counting uncertainty, which was also expected and is almost impossible to reduce without extension of the time required for an analysis. The expanded uncertainties were determined as 7.4% and 12.2% for ²¹⁰Pb and ²¹⁰Po, respectively. Received: 3 September 2002 Accepted: 3 December 2002 Acknowledgement This work was financially supported by Ministry of Education, Science and Sport, Republic of Slovenia (Project group PO-0106–0532). Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia Correspondence to P. Vreˇcek     

Radiochemical determination of lead-210 in environmental water samples using Cerenkov counting

A relatively simple method has been developed for the determination of²¹⁰Pb via its -emitting daughter,²¹⁰Bi. Lead-210 was separated from interfering elements as lead sulphate. The precipitate was dissolved in an alkaline solution of EDTA and the Cerenkov signal produced by the build-up of²¹⁰Bi was counted 30 days after storage using tritium channel of a liquid scintillation counter. Cerenkov counting efficiency was found to be approximately 20%. A lower limit of detection of 5.1 mBq/1 (based on 3 of the background with 500 minute counting time) was achieved. Chemical recoveries in the range of 70–100% were determined gravimetrically. Interference associated with currently used methods is avoided. Data from from both spiked samples and natural samples are presented.     

Analysis of 210Pb and 210Po in Brazilian foods and diets

Radiochemical procedures for the analysis of ²¹⁰ Pb and ²¹⁰ Po in foods and diets are presented. Because of the low beta energy of ²¹⁰ Pb, its analysis was based on a separation of the daughter radionuclide ²¹⁰ Bi by precipitation of lead sulphate, ²¹⁰ Bi ingrowing and beta counting of this nuclide. ²¹⁰ Po analysis was based on wet dissolution of the sample, deposition onto silver disc and counting by alpha-spectrometry. Levels of these radionuclides in individual items and diets of selected university students were determined in order to evaluate the intakes of ²¹⁰ Pb and ²¹⁰ Po as well as the dose due to ingestion of foods and diets in São Paulo city.     

Purification of gallium from bismuth and polonium by melting under synthetic slags

A method for the purification of technical grade gallium from bismuth and polonium by melting under synthetic slags is proposed. The examination of the purification degrees of gallium from bismuth and polonium was carried out with the aid of radioactive tracers²¹⁰Bi and²¹⁰Po. In order to obtain a gallium-bismuth alloy a suitable apparatus was assembled. The conditions of melting were established. The optimum conditions for the purification of gallium were established and the purification degrees of gallium from bismuth and polonium were determined.     

Atmospheric deposition of 210Po and 210Pb in Malaysian waters during haze events

Biogenic burning as forest fire phenomena occurring from April to August each year in the Sumatra and Borneo islands are major sources of biogenic uranium–thorium decay series in marine systems. 30 samples were collected during the Ekspedisi Pelayaran Saintifik Perdana 2009 cruise (EPSP 2009 cruise) between 12th June and 1st August 2009 from the Straits of Malacca to the Sulu and Sulawesi Seas to study the effect of haze and the monsoon season on the deposition rate of ²¹⁰Po and ²¹⁰Pb in Malaysian waters. All samples were spiked with 1 ml of lead [Pb(NO₃)₂; 25 mg ml^?1] and 0.05 ml of Polonium-209 tracer (26.08 dpm ml^?1). ²¹⁰Po activity was determined by auto plating onto silver foil and counting using an alpha spectrometry system (Canberra model Alpha Analyst with a silicon-surface barrier detector). Lead that was collected via electrodeposition, formed lead sulphate (PbSO₄) precipitation. This precipitate was wrapped onto plastic discs and counted for ²¹⁰Pb beta activity using a gross alpha–beta counting system (Tennelec model LB-5100 low background gas-flowing anti-coincidence alpha/beta counter) after 1 month to allow bismuth ingrowths. The range of ²¹⁰Po activities varied between 51.08 ± 15.1 and 742.08 ± 220.34 Bq/kg, whereas the activity of ²¹⁰Pb ranged from 31.10 ± 4.20 to 880.23 ± 123.86 Bq/kg and ²¹⁰Po/²¹⁰Pb ratio value varied between sampling stations from 0.19 to 13.77. The contents of ²¹⁰Po were also statistically positively correlated with the amount of total suspended particulate especially those recorded during heavy haze period events.     

Improvements on the method for determining of <Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po in lead

An improved method is proposed to determine the content of ²¹⁰Pb in lead using ²¹⁰Po measured by alpha-ray spectrometry. This improved method, which is based on radiochemical separation by DDTC–toluene extraction, employs EDTA and citrate as masking reagents for the lead ions. To selectively extract polonium from an alkaline solution, the pH dependency was examined using a liquid scintillation counting method. And pH 9 was chosen as an extraction condition. Then ²¹⁰Po was electrodeposited on a stainless steel disk, and the chemical recovery was followed by ²⁰⁹Po tracer. The effectiveness of the new method was validated by the agreement with the analytical results from five samples as determined by gamma-ray spectrometry.     

An improved sensitive assay for polonium-210 by use of a background-rejecting extractive liquid-scintillation method

A procedure is described for the determination of polonium-210 in various types of materials, including ores, mill tailings, and environmental samples, by a combined solvent-extraction liquid-scintillation spectrometry method. Concentration of polonium-210 and separation from interfering elements (such as iron) are accomplished by extraction from a 7M phosphoric acid-0.01M hydrochloric acid solution with 0.20M trioctylphosphine oxide solution (together with a scintillator) in toluene. The polonium-210 is determined by counting the 5.3-MeV alpha-radiation with a photon/ electron-rejecting alpha liquid-scintillation spectrometer. Extraction coefficients of over 1000 for polonium ensure quantitative recovery, and no other alpha-emitters in the decay chains of uranium-238, uranium-235 and thorium-232 are extracted. The results for several samples show the relative standard deviation to be approximately 1.2%. A lower limit of detection of 0.0038 pCi is proposed, based on a counting time of 1000 min and an easily obtainable background of 0.01 cpm for the alpha peak.     

Volatility of 210Po in the gross alpha determination

Gross alpha and beta activity screening methods have been developed to determine whether specific analysis of radionuclides is required to further characterize water. Our contribution aims at the validation of possible losses of ²¹⁰Po related to underestimation of the gross alpha activity. The tap water samples likewise the selected samples of surface, underground, and mineral water were processed. These samples were treated in solutions containing both HNO₃ (recommended by ISO standards) and HCl (which could cause significant loses of volatile polonium chloride form during the sample ignition). Results of several experiments determining the recovery of polonium during the ignition of sample are discussed. Conditions which can lead to significant losses of polonium are partly demarcated.     

Distribution of137Cs in soil in Central Slovakia and fast prediction of contamination

This paper describes the measurement of²¹⁰Bi by Cerenkov counting in a commercial liquid scintillation counter. The counting efficiency in water is 0.17 counts per second per Becquerel (17%). When the enhancers Triton X-100 (15% v/v) and sodium salicylate (1% m/v) are added to the solution the counting efficiency for²¹⁰Bi increases from 17% to 75%. The²¹⁰Po daughter of²¹⁰Bi causes interference of 0.85 counts per second per Becquerel in the presence of the enhancers but not in water. When²¹⁰Bi and²¹⁰Po are present in secular equilibrium the total counting efficiency is 160%. When²¹⁰Bi and²¹⁰Po are not in secular equilibrium the²¹⁰Po can be removed immediately before counting by plating onto silver foil. The use of the enhancers gives a substantial increase in counting efficiency compared to counting in water. Compared with solutions used in liquid scintillation counting the enhancer solution is inexpensive and can be disposed of without environmental hazard.     

Determination of210Pb in sediments by extraction chromatography

A selective method is described for the determination of²¹⁰Pb in sediments, based on the separation of the daughter²¹⁰Bi by extraction chromatography with Microthene 710-tri-n-octylphosphine oxide (TOPO) and on a final source counting with a low background -counter. The average chemical yield is 92.0%. The detection limit for 2 g samples is 19 Bq kg^–1. An IAEA reference sediment sample was analyzed to check the reliability of the method.     

Separation of the radioelements210Pb−210Bi−210Po by spontaneous deposition onto noble metals and verification by Cherenkov and liquid scintillation counting

A method for the separation of²¹⁰Pb,²¹⁰Bi and²¹⁰Po using spontaneous deposition has been developed. The²¹⁰Bi and²¹⁰Po are simultaneously removed by deposition onto nickel foil (copper and tin could also be used but less effectively) while the²¹⁰Po is separated from²¹⁰Bi, after dissolution of the nickel foil, by deposition onto silver foil. The effectiveness of each separation was evaluated by adding aliquot portions of each solution to a cocktail and counting with a liquid scintillation counter. Water was used as the medium to observe the Cherenkov count of the sample solution.     

Determination of polonium-210 in phosphoric acid

Polonium-210 in phosphoric acid has been recognized as a significant source of alpha contamination of processed Si-wafers for memory devices of computer. In the present work, a convenient method was developed for the determination of trace²¹⁰Po in phosphoric acid of high purity. For the determination,²⁰⁹Po was used as a yield tracer. The present method consists of (1) addition of the tracer to 5 ml aliquot of phosphoric acid sample, (2) pH adjustment (to 2) of the sample solution to make up electrolytic solution, (3) electrodeposition for the simultaneous achievement of Po separation and preparation of counting source on stainless-steel disc, and (4) alpha-ray spectrometry. By the developed method, more than 95% of Po was separated from phosphoric acid sample onto counting disc. The minimum detectable radioactivity of²¹⁰Po in 5 ml of phosphoric acid was about 0.03 mBq by counting the electrodeposited alpha-activity for 10 days under a counting efficiency of ≈30%.     

Synthesis,storage, and transfer of [210Pb]-(CH3)3PbCl across tomato fruit cuticle

An improved synthetic route to [²¹⁰Pb]-(CH₃)₃PbCl is described in which chelated ²¹⁰Pb²⁺ is methylated to [²¹⁰Pb]-(CH₃)₄Pb with methylmagnesium bromide (CH₃MgBr) in the presence of methyl iodide. Controlled oxidation of the product with anhydrous hydrochloric acid and purification of the crude product by reversed-phase high-pressure liquid chromotography (HPLC) resulted in [²¹⁰Pb]-(CH₃)₃PbCl in 71% radiochemical yield. Whereas storage of the purified product at ?10 °C resulted in complete conversion to Pb²⁺ during one year, storage in 20% acetic acid at 4 °C resulted in less than 15% decomposition during six months. Periodic complexometric extractions to remove ²¹⁰Pb radioactive daughters (²¹⁰Bi, 100% β, E_max = 1.16 MeV; ²¹⁰Po, 100% α, E = 5.305 MeV) from the storage solution did not alter the rate of decomposition. The rate of translocation of [²¹⁰Pb]-(CH₃)₃Pb⁺ across an isolated tomato cuticle was approximately twice the rate of transfer of inorganic lead(II) and was not influenced by the presence of increasing amounts of disodium ethylenediamine-tetra-acetate.     

The role of Cherenkov and liquid scintilation counting in evaluating the anion-exchange separation of210Pb−210Bi−210Po

Using as eluent a sequence of 3M HCl, 12M HCl, and 8M HNO₃, a mixture of²¹⁰Pb,²¹⁰Bi, and²¹⁰Po may be clearly separated on a column of Dowex 1×2−100 anion exchange resin. A Cherenkov count in H₂O and the variation in count rate with time confirm that the nuclides emerge in the order²¹⁰Pb→²¹⁰Bi→²¹⁰Po. If 12M HCl is replaced by 1.5M H₂SO₄/2.3 M Na₂SO₄, a clean separation also results, but recovery of²¹⁰Po becomes considerably more difficult. All three nuclides are readily detectable by liquid scintillation counting, with the efficiency for²¹⁰Pb in the 60–70% range. The Cherenkov aqueous counting efficiency for²¹⁰Bi is ∼14–15%.     

Mutual separation of210Po,210Bi,and210Pb with solvent extraction using copper dithizonate −CCl4 and dithizone −CCl4 solutions

Displacement-extraction of tracer concentrations of²¹⁰Po in 1.0M (H, Na)NO₃ solutions has been studied by using copper dithizonate–CCl₄ solutions. Furthermore, based on the results of the displacement-extraction of polonium, a mixture of²¹⁰Po,²¹⁰Bi, and²¹⁰Pb of tracer concentrations in 1.0M (H, Na)NO₃ solutions could be satisfactorily separated with successive extractions by copper dithizonate–CCl₄ and dithizone–CCl₄ solutions in acidic conditions.     

Development of a sequential method for the determination of238U,234U,232Th,230Th,228Th,228Ra,226Ra,and210Pb. in environmental samples

A sequential analytical method for the determination of²³⁸U,²³⁴U,²³²Th,²³⁰Th,²²⁸Th,²²⁸Ra,²²⁶Ra and²¹⁰Pb in environmental samples was developed. Uranium and thorium isotopes are first chromatographically sepaaated using tri-n-octyl phosphine oxide (TOPO) supported on silica gel. The uranium isotopes are determined by alpha-spectrometry following extraction with TOPO onto a polymeric membrane. Thorium isotopes are co-precipitated with lanthanum fluoride before counting in an alpha spectrometer. Radium isotopes and²¹⁰Pb are separated by co-precipitation/precipitation with mixed barium/lead sulphate. Radium-226 is determined by gross alpha counting of the final BaSO₄ precipitate and²²⁸Ra by gross beta counting of the same source. Lead-210 is determined through beta counting of its daughter product²¹⁰Bi.     

Separation of carrier-free210Bi and UX1 from210Pb and U,respectively, using silica gel as ion exchanger

Radiochemical separations of carrier-free²¹⁰Bi and UX₁ activities from²¹⁰Pb and U, respectively, have been carried out using a silica gel column.²¹⁰Pb was adsorbed in the column as molybdate and²¹⁰Bi passed unadsorbed. Lead activity was next removed with 25 ml of 0.1 M HNO₃. In the case of separation of UX₁, the coloured carbonate complex of U was removed from the silica surface by washing with saturated sodium carbonate solution, keeping UX₁ retained, and finally UX₁ was washed out with 25 ml of conc. HNO₃. Studies of the beta decay of²¹⁰Bi and the γ-spectrum analysis of UX₁ has shown that the separated products in both cases are of high radiochemical purity. The processes in each case took less than one hour and the yield was satisfactory.