Simultaneous liquid scintillation determination of239Pu and241Am in tissue

A liquid scintillation counting method for the simultaneous determination of Pu and Am, with a two-phase cocktail, has been applied to the analysis of a tissue sample from an accidental exposure incident. The sample contained²³⁹Pu,²⁴¹Pu, and²⁴¹Am. In addition to analysis by two liquid scintillation counting techniques, analysis of the sample was performed by -spectroscopy and ZnS scintillation techniques, and the results were compared. The presence of²⁴¹Pu interfered with the liquid scintillation determination of²⁴¹Am when the two-phase cocktail was used, but the results were in agreement sufficient to be useful in determining what course of treatment, if any, might be necessary for the patient.     

Determination of 241Pu in marine samples using co-precipitation with rare earth fluoride and liquid scintillation spectrometry

²⁴¹Pu was measured in reference materials and marine samples using a novel method based on rare earth fluoride co-precipitation followed by liquid scintillation spectrometry (LSS). Disc sources used for -spectrometry of ²³⁸Pu and ^239+240Pu were leached with concentrated nitric acid before neodymium fluoride co-precipitation to scavenge plutonium in the lower oxidation states was carried out. After the determination of the chemical recovery by -spectrometry, the precipitate was recovered in a H₃BO₃/HNO₃ based dissolver and mixed with Packard Insta-Gel^Ò Plus cocktail before LSS. Reasonable agreement has been obtained between the results obtained using this methods and the data obtained by direct disc analysis by LSS and ICP-MS. The ²⁴¹Pu/^239+240Pu ratios were coherent with the expected origin of the Pu contaminant in the marine environment showing the validity of the method.This revised version was published online in November 2005 with corrections to the Cover Date.     

Rapid measurement of 241Pu activity at environmental levels using low-level liquid scintillation analysis

A straightforward and rapid method has been developed for the determination of ²⁴¹Pu activities. Pu is chemically separated from the sample, purified and electrodeposited to produce a source for alpha spectrometric determination of ²³⁸Pu and ^239,240Pu. Pu is stripped from the disc with concentrated nitric acid and extracted into tri-octylphosphine oxide (TOPO)/toluene. The organic extract is then mixed directly with commercial liquid scintillation cocktail without any further purification procedures and the sample counted on a Wallac 1220 Quantulus liquid scintillation counter (LSC). ²⁴¹Pu activity is estimated via the ²⁴²Pu yield monitor acquired by alpha spectrometry measurement. Experimental results for the performance testing of a low-level liquid scintillation spectrometer and the data for the evaluation of the method using standard reference materials are presented.     

Increasing the sensitivity of241Pu determination for emission and immission control of nuclear installations by aid of liquid scintillation counting

A radiochemical procedure was developed and optimized which allows sensitive²⁴¹Pu measurement in various sample materials. As a first step, Pu isotopes are separated from matrix elements, purified radiochemically, electroplated, and measured by -spectrometry. The electrodeposited Pu is then redissolved in nitric acid and extracted with trioctylphosphinic oxide/cyclohexane. The organic phase is mixed with scintillator cocktail (PPO/Xylene) and Pu is measured with a liquid scintillation counter. The detection limit of the optimized procedure for a counting time of 100 minutes is 50 mBq²⁴¹Pu per sample at a 95% confidence level.     

Simultaneous determination of 152Eu and 241Am in liquid solution by liquid scintillation counting

¹⁵²Eu and ²⁴¹Am are the most frequently used radiotracers in the separation studies on trivalent minor actinides and lanthanides. In almost all those studies, the determination of ¹⁵²Eu and ²⁴¹Am has been based on measuring their γ radiation by using a NaI(Tl) scintillation detector and/or a germanium detector. In this study, based on measuring the β particles and mono-energy electrons from ¹⁵²Eu and the α particles from ²⁴¹Am, we provide a new option to simultaneously determine the radioactivities of ¹⁵²Eu and ²⁴¹Am by liquid scintillation counting (LSC) with the aid of α/β discrimination. If the count rate ratio of ²⁴¹Am to ¹⁵²Eu is within the range of 100:1–1:100, the radioactivities of ¹⁵²Eu and ²⁴¹Am in mixed samples can be simultaneously determined by LSC with the errors less than 5 %. In addition, the interferences of ²⁴¹Am on Eu are divided into two parts: inside and outside the ²⁴¹Am region of interest. Only if the count rate ratio of ²⁴¹Am to Eu is more than 10:1, should the latter interference be in consideration.     

Determining the activity of <Superscript>241</Superscript>Pu by liquid scintillation counting

Liquid scintillation counting (LSC) is one of the most widely used methods for determining the activity of ²⁴¹Pu. One of the main challenges of this counting method is the efficiency calibration of the system for the low beta energies of ²⁴¹Pu (E _max = 20.8 keV). In this paper we compare the two most frequently used methods, the CIEMAT/NIST efficiency tracing (CNET) method and the experimental quench correction curve method. Both methods proved to be reliable, and agree within their uncertainties, for the expected quenching conditions of the sources.     

Multi-isotopic determination of plutonium (239Pu, 240Pu, 241Pu and 242Pu) in marine sediments using sector-field inductively coupled plasma mass spectrometry

Among the transuranic elements present in the environment, plutonium isotopes are mainly attached to particles, and therefore they present a great interest for the study and modelling of particle transport in the marine environment. Except in the close vicinity of industrial sources, plutonium concentration in marine sediments is very low (from 10⁻⁴ ng kg⁻¹ for ²⁴¹Pu to 10 ng kg⁻¹ for ²³⁹Pu), and therefore the measurement of ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴²Pu in sediments at such concentration level requires the use of very sensitive techniques. Moreover, sediment matrix contains huge amounts of mineral species, uranium and organic substances that must be removed before the determination of plutonium isotopes. Hence, an efficient sample preparation step is necessary prior to analysis. Within this work, a chemical procedure for the extraction, purification and pre-concentration of plutonium from marine sediments prior to sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) analysis has been optimized. The analytical method developed yields a pre-concentrated solution of plutonium from which ²³⁸U and ²⁴¹Am have been removed, and which is suitable for the direct and simultaneous measurement of ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴²Pu by SF-ICP-MS.     

Determination of plutonium-239 + plutonium-240 and plutonium-241 in environmental samples using low-level liquid scintillation spectrometry.

A radiochemical method for the simultaneous determination of 239Pu + 240Pu and 241Pu in environmental samples has been developed. In the course of the analysis a 236Pu tracer was used for estimating the chemical yield of plutonium isotopes. After suitable pre-treatment of the sample, the plutonium nuclides in solution were coprecipitated with iron(III) hydroxide and calcium oxalate and isolated further from impurities and interfering radionuclides by means of anion-exchange chromatography. Plutonium isotopes in the eluate (NH4I-HCI) were converted into nitrate form and then extracted with 20 ml of 5% bis(2-ethylhexyl) hydrogen phosphate extractive cocktail. The final organic solution was measured spectrometrically using an ultra-low-level liquid scintillation spectrometer, Quantulus (LKB, 1220 Wallac). The chemical yields of plutonium range from 25 to 50% for 100 I of sea-water and 30 to 60% for 40 g of dried soil sample. The counting efficiencies are nearly 100% for 239Pu + 240Pu and 48.8% for 241Pu, respectively. The detection limits were estimated to be 0.20 mBq for 239Pu + 240Pu and 2.2 mBq for 241Pu, respectively. The proposed procedure has been tested for the simultaneous determination of 239Pu + 240Pu and 241Pu in sea-water (Irish Sea, North Sea) and soils (Cumbrian coast, UK; Byelorussia, USSR).     

Indirect determination of241Pu activity in soils using low energy photon spectrometers

Actinides activity levels deposited after the Chernobyl accident on the coastal Mediterranean area at Monaco have been recently measured (1). The values obtained are low. However, our -measurements on humic soils from the southern Alps revealed high¹³⁷Cs level contamination areas and urged us to evaluate²⁴¹Pu activity levels. The indirect determination of²⁴¹Pu was based on the -activity measurement of the²⁴¹Am in situ ingrown.     

Analysis of long-lived isotopes by liquid scintillation spectrometry

Neutron production cross sections are reported for reactions leading to long-lived isotopes in fusion reactor materials. Pure elements and separated isotopes were irradiated with 14.6–14.8 MeV neutron fluences up to 10¹⁸ n/cm². Undesired activities were chemically separated and the long-lived activities were measured using both liquid scintillation and x-ray spectrometry. Results are presented for the reactions⁵⁶Fe(n,2n)⁵⁵Fe(2.73 y),⁶⁴Ni(n,2n)⁶³Ni(100 y),⁶³Cu(n,p)⁶³Ni, and⁶⁰Ni(n,2n)⁵⁹Ni(76,000 y).Work supported by the U.S. Department of Energy.     

Alpha liquid scintillation measurement of plutonium in solution spiked by236Pu

The liquid-liquid extraction method used with alpha liquid scintillation with rejection of -emission is strongly dependent of the nature of the aqueous solution containing actinides. We propose to measure plutonium quantitatively by its labelling with²³⁶Pu. Two procedures of quantitative extraction have been developed as well as the mathematical fit to obtain accurate results. The limits of detection have been determined for several counting times like for instance 0.2 pg/l after one day of acquisition time. We have applied both procedures successfully for the determination of plutonium in doped drinking water and in solid samples after dissolution.     

Determination of thoron and radon ratio by liquid scintillation spectrometry

Summary A portable liquid scintillation counter was applied for the analysis of alpha-ray energy spectrum to determine the ratio of ²²⁰Rn/²²²Rn in fumarolic gas in the field. A surface-polished vial was developed, by which a Gaussian distribution could be approximated for the alpha-ray energy spectra and the peak areas of the nuclides could be estimated independently, because of the wide FWHM in the liquid scientillation pulse. A fumarolic gas sample was collected in Mt. Kamiyama (Hakoneyama geothermal field in Japan) having low ²²⁰Rn/²²²Rn ratio of 2.20±0.13.     

Radiometric determination of trace amounts of zinc using liquid scintillation counting

A sensitive and selective radiometric method of substoichiometric isotope dilution analysis for the determination of trace amounts of zinc is described. The activity of (65)Zn used as a tracer in this method was measured by liquid scintillation counting and its counting efficiency was found to be 76+/-2.7%. The method is based on the extraction of the ion-association complex of zinc from thiocyanate medium at pH 7.9 using substoichiometric amount of Aliquat-336 in toluene. The method is sensitive to 20 ng of Zn(II) in an aqueous phase volume of up to 15 ml and its reliability was tested by applying it to a certified reference material-magnesium alloy and pharmaceutical samples.     

Radon determination by activated charcoal adsorption and liquid scintillation measurement

A passive diffusion method for the determination of radon concentration has been optimised and calibrated. The device consists of a scintillation vial containing activated charcoal, a diffusion barrier and a desiccant agent. The response to diverse atmospheric humidity and variable exposure intervals was studied. The result is a detector independent of atmospheric humidity till 7 days of exposure. The method was compared with electret detectors (US EPA) with very satisfactory results. The advantages of this method are its simplicity, low cost, low detection limit, the total automatization of the measurement and its total independence of humidity to measure in a wide range of radon concentrations.     

Improved method for the determination of the cortisol production rate using high-performance liquid chromatography and liquid scintillation counting

Two new methods for the determination of the cortisol production rate using reversed-phase high-performance liquid chromatography are described. One uses ultraviolet detection at 205 nm, the other on-line post-column derivatization with benzamidine, followed by fluorimetric detection. The specific activity of tetrahydrocortisol and tetrahydrocortisone in urine from patients who had received tritium-labelled cortisol was determined by the indicated methods, followed by fraction collection and liquid scintillation counting. The post-column reaction detection procedure was superior to ultraviolet detection, both in selectivity and analysis time. Intra- and inter-assay variance of the post-column reaction detection procedure were 3.7 and 4.7%, respectively. A good correlation (r = 0.99) was obtained between values determined by this procedure and by a thin-layer chromatographic procedure.     

Simultaneous determination of alpha and beta-emitting nuclides by liquid scintillation counting

The determination of - and -emitting nuclides has been studied with a commercial liquid scintillation counter /Tri-Carb 2200CA/ equipped with Pulse Shape Analysis /PSA/. The results indicated that the efficiency for -emitters is virtually 100% and discrimination for -emitters is more than 99.9%. Liquid scintillation counting with PSA can be used for the determination of - and -emitting nuclides simultaneously.     

Fast determination of 90Sr using liquid scintillation counter based on shielding package

Journal of Radioanalytical and Nuclear Chemistry - A novel method for direct measurement of 90Sr in liquid samples was developed by using liquid scintillation counter. Based on the shielding...     

Study of the factors affecting the performance of microextraction by packed sorbent (MEPS) using liquid scintillation counter and liquid chromatography-tandem mass spectrometry

Microextraction by packed sorbent (MEPS) is a new technique for sample preparation that can be connected on-line with LC or GC. In MEPS, approximately 1-2 mg of the solid packing material is inserted into a syringe (100-250 μL) as a plug. Sample preparation takes place on the packed bed. The bed can be packed or coated to provide selective and suitable sampling conditions. The new method is very promising for extraction of drugs and metabolites from biological samples.In this paper, some factors affecting the performance of MEPS such as recovery, carry-over, leakage, washing volume and elution volume were studied using C18 and hydroxylated polystyrene-divinylbenzene copolymer (ENV+) as sorbents. Radioactively labelled bupivacaine in plasma samples was used as test analyte. For the extraction of this drug, using methanol/water 95:5 (v/v) (0.25% ammonium hydroxide) was used as elution solvent. The analyte response increased with increasing the elution volume and it was linear upp up to 100 μL utilizing liquid scintillation counter. Further, for concentrating the sample, we found that MEPS may be used such that the sample can be drawn through the needle, up and down, several times. The analyte leakage increases as the volume washing increases, though higher washing volumes may also result in cleaner extracts. To eliminate analyte carry-over, the sorbents were washed first with 3 × 250 μL elution solution and then with 3 × 250 μL washing solution. In addition, the reproducibility measurements show relatively good relative standard deviation (RSD) % values concerning analyte recovery and analyte leakage. The present study provides an understanding of basic aspects when optimizing methods for MEPS. In this study, MEPS was used off-line with liquid scintillation counter and on-line with LC-MS/MS.     

High throughput log D determination using liquid chromatography-mass spectrometry

A method has been developed which allows direct measurement of partition coefficients (log D, log P) using liquid chromatography-mass spectrometry (LC-MS). The high throughput, microtiter plate based protocol uses small quantities of 10 mM analyte in DMSO solution (5 microL) and is therefore amenable to standard archive and screening formats. Single Ion Monitoring (SIM) mass spectrometry is used to achieve optimal sensitivity. Experimental log D values for 34 known drugs have been determined, with partition coefficients ranging from -2 to 5, giving data very similar to literature values. In these analyses, deviations from known values average less than 0.3 log units. The sample handling and data processing have been significantly automated, and the protocol has been applied to over 800 in-house lead molecules to date. In its format, sensitivity, throughput, and amenability to automation, it represents significant progress in the direct measurement of partitioning behavior [1].