N. P. Singh

Determinations of actinides in biological and environmental samples

This paper summarises the radiochemical procedures utilised in our laboratory to determine U, Th and Pu in different sample matrices, including soft tissues, bones, urine, faeces, soil, water, air-filters, lichen, and building materials such as granite, phosphate and concrete. Sample preparation, depending upon the matrix of the sample, includes either dry ashing and/or wet ashing with a mixture of HNO3 and H2SO4 or HNO3 alone with occasional additions of a few drops of HNO3 and H2O2. Uranium, Th and Pu are either co-precipitated with Fe carrier as hydroxides or with Ca as oxalates. Solvent extractions are performed from 2M HNO3, 4M HNO3 or 10M HCl depending upon the actinide or combination of actinides to be determined. The techniques have been very successful for most samples, with radiochemical recoveries exceeding 70%. However, radiochemical recoveries of Th from soil samples have been very poor (10-30%). Attempts are being made to improve these recoveries.

Simultaneous determinations of alpha-emitting isotopes of uranium and plutonium in bone

A radiochemical procedure has been developed for the simultaneous determinations of alpha-emitting isotopes of uranium and plutonium in bovine bone. The radiochemical recoveries ranged from 61 to 93% with a mean of 80±10% for uranium and 57 to 88% with a mean of 75±11% for plutonium. The method was successfully used for human bone.

Background levels of uranium in human urine

The literature on the normal content of uranium in urine is reviewed. The reported normal concentration has declined several orders of magnitude over the years, probably due to improvements in analytical technique rather than a real change. The lowest mean values were reported with α spectrometry (mean of 23 ng/l in 12 subjects) and thermal ion mass spectrometry (3.4 ng/l in 1 subject). Even α spectrometry is not sufficiently sensitive at normal levels, so that techniques such as fission track analysis or mass spectrometry must be used to obtain results above the detection limit of the technique for individual samples.

Thorium, uranium and plutonium in human tissues of world-wide general population

The results on the concentrations of thorium, uranium, and plutonium in human tissues of world-wide general populations are summarized. The majority of thorium and uranium are accumulated in the skeleton, whereas, plutonium is divided between two major organs; the liver and skeleton. However, there is a wide variation in the fractions of plutonium in the liver and the skeleton of the different populations.

Quantitative determination of environmental levels of uranium, thorium and plutonium in bone by solvent extraction and alpha spectrometry

Abstract Solvent extraction and alpha-spectrometry have been emplyed in the quantitative simultaneous determination of uranium. thorium and plutonium. The bone specimens, spiked with 232 U, 229 Th and 242 Pu tracers, are wet ashed with HNO 3 followed by alternate additions of a new drops of HNO 3 and H 2 O 2 . Uranium is reduced to the tetravalent state with 200 mg SnCl 2 and 25 ml HI. Uranium, thorium and plutonium are then coprecipitated with calcium as oxalate, heated to 550°C, dissolved in 50 ml HCl, and the acidity adjusted to 10 M. Uranium and plutonium are extracted into a 20% tri-lauryl amine (TLA) solution in xylene, leaving thorium in the aqueous phase. Plutonium is first back-extracted from the TLA phase by shaking with a 1:1.5 volume of 0.05 M NH 4 I in 8 M HCl, which reduces Pu(IV) to Pu(III). Uranium is then back-extracted with an equal volume of 0.1 M HCl. Thorium, which was left in the aqueous phase, is evaporated to dryness, dissolved in 4 M HNO 3 , and the acidity adjusted to 4 M. Thorium is then extracted into 20% TLA solution in xylene pre-equilibrated with 4 M HNO 3 , and back-extracted with 10 M HCl. Uranium, thorium, and plutonium are then electrodeposited separately onto platinum discs and counted by an alpha-spectrometer with a multi-channel analyzer and surface barrier silicon diodes. The mean recoveries of uranium, thorium, and plutonium in bovine, dog, and human bones were over 70%.

Determination of alpha-emitting uranium isotopes in soft tissues by solvent extraction and alpha-spectrometry.

A radiochemical procedure has been developed for the determination of alpha-emitting isotopes of uranium ((238)U, (235)U and (234)U) in soft tissues. Known amounts of sample are spiked with (232)U internal tracer and wet-ashed. Uranium is co-precipitated with iron hydroxide as carrier, and extracted into 20% trilaurylamine solution in xylene after dissolution of the precipitate in 10M hydrochloric acid. The uranium, after stripping into an aqueous phase, is electro-deposited onto a platinum disc and counted by alpha-spectrometry. The radiochemical recovery ranges from 60 to 85% for bovine liver samples. The average radiochemical recoveries for human tissues vary from 53 to 78%.

PIXE-RBS combination to measure uranium and thorium in environmental and biological samples

A combination of two techniques, PIXE (particle induced x-ray emission) and RBS (Rutherford backscattering), is proposed as an analytical tool to measure uranium and thorium in environmental and biological samples and in the study of the micro-distribution of uranium is low Z matrices such as biological tissue.

Localization of Vanadium-Containing Particles in the Lungs of Uranium/Vanadium Miners

Several geological formations of the Utah-Colorado mining region mined for uranium ore during and after World War II had been mined earlier for vanadium. Therefore, most miners and millers from that region were exposed to those metals’ ores or tailings at one time or another. Preliminary investigation to determine uranium and vanadium retained in the lungs of a former uranium miner and miller from this region, who died of lung cancer (mesothelioma), showed a high nonuniform distribution of vanadium. This observation led to the hypothesis that the vanadium content in the lungs could be associated with inhaled particles. Further examination of spectra of characteristic X-rays obtained by scanning particle-induced X-ray emission (microPIXE) of an autopsy sample of this lung indicated that vanadium was indeed present in localized sites within the 20-μm spatial resolution of the proton beam. This work points out that the microPIXE-RBS (Rutherford backscattering) test for vanadium can be used for site localization of inhaled particles retained in the lungs. Further studies are in progress to: (i) locate uranium-bearing particles in lung tissues of former uranium miners and millers; and (ii) evaluate the local doses of alpha radiation received from these particles.

Simultaneous determination ofα-emitting isotopes of uranium and plutonium in soft tissues

SummaryA simple radiochemical procedure has been described for the simultaneous determination ofα-emitting isotopes of uranium and plutonium in soft tissues. The weighed amounts of tissue, spiked with232U and242Pu tracers, were wet ashed. Uranium and plutonium were coprecipitated with iron, dissolved in HCl and the acidity adjusted to 10M. They were co-extracted into 20% tri-lauryl amine (TLA) solution in xylene. Plutonium was back-extracted first with 8M HCl containing 0.05M NH4I and then uranium was backextracted with 0.1M HCl. They were electrodeposited separately on platinum discs and counted byα-spectrometry. The average recoveries of uranium and plutonium were 74% or more. Most importantly, there was no uranium on the platinum disc containing plutonium and vice-versa.ZusammenfassungZur radiochemischen Bestimmung derα-emittierenden Isotopen des Urans und des Plutoniums in weichen Geweben werden diese gewogen, mit Spuren232U und242Pu versehen und naß verascht. U und Pu werden gemeinsam mit Eisen gefällt und in Salzsäure gelöst. Die Acidität wird auf 10M eingestellt. Dann wird in eine 20% ige Lösung von Trilaurylamin in Xylol extrahiert. Plutonium wird daraus zuerst mit einer Lösung von 0,05M NH4J in 8M HCl, dann das Uran mit 0.1M HCl rückextrahiert. Dann wird dieα-Strahlung beider auf Platinscheibchen abgeschiedener Spurenmetalle gemessen. Durchschnittlich werden Uran und Plutonium zu mindestens 74% wiedergefunden. Wichtig ist natürlich, daß die Platinscheibchen kein Plutonium bzw. kein Uran enthalten.

Amines as extracting agents for the quantitative determinations of actinides in biological samples

The present manuscript reviews the use of amines (primary, secondary and tertiary chains and quaternary ammonium salts) as extracting agents for the quantitative determination of actinides in biological samples. Among the primary amines, only Primene, JM-T is used to determine Pu in urine and bone. No one has investigated the possibility of using secondary amines to quantitatively extract actinides from biological samples. Among the tertiary amines, tri-n-octylamine, tri-iso-octylamine, tricaprylamine (Alamine) and trilaurylamine (tridodecylamine) are used extensively to extract and separate the actinides from biological samples. Only one quanternary ammonium salt, methyltricapryl ammonium chloride (Aliquat-336), is used to extract Pu from biological samples.