Measuring technique for thermal ionisation mass spectrometry of human tracer kinetic study with stable cerium isotopes

Thermal ionisation mass spectrometry (TIMS) method has been developed for the simultaneous detection of different cerium isotopes in biological samples (i.e., blood and urine) at very low concentrations. The work has been done in the frame of a biokinetic study, where different stable cerium isotopes have been administered orally and intravenously as tracers to the human body. In order to develop an appropriate detection method for the tracers in the biological samples, an optimum sample preparation technique has been set and adapted to the specific requirements of the analysis technique used, i.e., TIMS. For sample evaporation and ionisation, the double tantalum filament technique showed the best results. The ions produced were simultaneously collected on a secondary electron multiplier so that the isotopic ratios of the cerium isotopes in the biological samples could be measured. The technique has been optimised for the determination of cerium down to 1?ng loaded on the evaporation filament corresponding to cerium concentrations of down to 1?ng?ml(-1) in the blood or urine samples. It has been shown that the technique is reliable in application and enables studies on cerium metabolism and biokinetics in humans without employing radioactive tracers.     

Thermal Ionization and Inductively Coupled Plasma Mass Spectrometry: Potential for Application to Studies on the Biokinetics of Molybdenum in Humans

Abstract

The use of stable isotopes as tracers in biokinetic investigations provides a means to obtain important metabolic data directly in humans without exposing the subjects to undue risks. In this work, three types of mass spectrometers are compared with regard to the determination of the abundances of stable isotopes of molybdenum in natural and enriched aqueous samples. The data show a good response of thermal ionization mass spectrometry (TIMS) and of high-resolution inductively coupled plasma mass spectrometry (ICPMS) to the isotopic enrichment of the samples, whereas conventional quadrupole ICPMS shows an unsatisfactory reproducibility of the results. Moreover, only TIMS can achieve an accuracy of better than 1% for the obtained isotopic ratios. Although a tedious procedure for the preparation of the biological samples is required and less sensitivity is achieved as compared to ICPMS, TIMS still seems to be method of choice for the accurate assessment of isotope ratios as required in multitracer studies on human biokinetics of trace metals.     

Radioanalytical determination of 239+240Pu and 241Am in bioassay samples by anion exchange and extraction chromatography: Preliminary considerations about the two methods

During the radiation protection surveillance of exposed workers samples of urine and faeces were collected. Anion exchange chromatography was used for the separation of Pu. We investigated a technique to purify and separate Pu and Am isotopes using extraction chromatography with TRU resin. We tested different procedures to dissolve organic matter and eliminate interferences for chromatographic elution. At the end of the proces we have succeeded in electroplating the two radionuclides separately. We have also studied extraction chromatography with UTEVA resin to purify Pu isotopes and separate it from natural uranium radioisotopes, present in some biological samples. We validated a method for the determination of Pu in biological samples and a rather constant chemical yield and resolved peaks were obtained. The preliminary studies on TRU resin have indicated that it is possible to combine extraction and anion-exchange chromatography for analysing separately Pu and Am isotopes from the same sample aliquote.     

Hydrochemistry and boron isotopes as natural tracers in the study of groundwaters from North Chianan Plain,Taiwan

In this paper, hydrochemistry and boron isotopes are successfully applied to elucidate hydrogeological processes by the use of natural tracers. The hydrochemical analysis identifies four end-members in the hydrochemical evolution of groundwater from the North Chianan plain groundwater district. A few groundwater contain extraordinary chlorine concentrations of up to 48,000 mg l^?1. However, the hydrochemistry of groundwater only reveals that high saline water is a dominant factor in groundwater hydrochemistry. It is thought that these groundwater experienced precipitation of carbonates during seawater evaporation that did not involve the precipitation of gypsum. Boron isotopes are very efficient tracers in determining the source of salinisation. The boron isotopes reveal the results of mixing of evaporated seawater and water–sediment interaction. In general, the boron isotope ratio of the groundwater is controlled by a two-end-member mixing system, which is composed of evaporated seawater (isotopically heavy) and fresh surface water (isotopically light). Due to a long lagoonal period in the coastal plain, the groundwaters in the downstream area generally have high Cl/B ratios and relatively heavy boron isotope ratios while those in the upstream area are composed of low Cl/B and light boron isotopes. However, there is not a resolvable mixing trend between the Cl/B ratio and the isotopic composition of boron. It is probably obscured by a highly variable boron isotope ratio in fresh surface water and through fractionation associated with water–rock interaction. Both factors would decrease the boron isotope ratio but one effect cannot be distinguished from the other.     

Atom trap trace analysis

A new method of ultrasensitive isotope trace analysis has been developed. This method, based on the technique of laser manipulation of neutral atoms, has been used to count individual ⁸⁵Kr and ⁸¹Kr atoms present in a natural krypton gas sample with isotopic abundances in the range of 10⁻¹¹ and 10⁻¹³, respectively. The method is free of contamination from other isotopes and elements, and can be applied to many different isotope tracers for a wide range of applications. This revised version was published online in August 2006 with corrections to the Cover Date.     

Can an IR Diode Laser Spectrometer be Used for the Determination of Natural Isotope Ratios in Biological Samples?

Abstract

An IR diode laser spectrometer can detect the enrichment of stable isotopes (¹³C [1] and ¹⁵N[2]) in tracer studies. However our system cannot detect differences of the natural abundances of these isotopes. This problem is not a principal limitation of the IR diode laser spectroscopy, but is inherent to our standard system. A new isotope ratio IR diode laser spectrometer has an accuracy high enough for most biological applications. Some advantages like flexibility in measuring different isotopes, insensitivity against other gases in the sample and price are correlated to this system.     

Isotope Studies of Hydrogen and Oxygen in Ground Ice - Experiences with the Equilibration Technique

Abstract

Equilibration technique suitable for a large amount ofsamples is described for hydrogen and oxygen isotope analyses of ground ice, especially ice wedges, including the sampling strategy and the analytical procedure as well as the calibration of the Finnigan MAT Delta-S mass spectrometer in June, 1999. Since for future analyses of ice wedges, a higher sampling resolution with limited sample volume is required, the limit of the equliibration technique for small water samples size of between 0.05 and 5 ml was checked. For water samples smaller than 1ml, corresponding to a molar ratio [H₂O]/[H₂] of smaller than 0.994, a balance correction has to be applied. The experimental errors due to partial evaporation during evacuation, the balance calcultion of the isotope equilibration process, the linearity as well as memory effects of the mass spectrometer for smaples with large differences in δ¹⁸O and δD are tackled in this paper. In the polar regions of Northern Siberia without Late Pleistocene and Holocene glaciation, ground ice is used as an archive for paleoclimate studies. First results of stable isotope measurements on ice wedges clearly show a shift towards heavier isotopes and thus warmer winter temperatures as well as a change in the source of the precipitation between Late Pleistocene and Holocene. These results indicate the high potential of ground ice for paleoclimate studies.     

Potential of total-reflection X-ray spectrometry for multielement analysis of biological samples using dilution or suspension sample preparation techniques

In most clinical and nutritional studies, it is of significance to know information about the multielemental composition of biological samples. Conventional analysis of biological samples relies upon sample digestion followed by atomic spectrometry detection. This approach is essential for the quantification of ultratrace elements in biological samples. While in other applications it could be of interest to have simpler analytical methods with multielemental capability but involving a minimum sample treatment, reduce the amount of sample and a more cost-effective analysis. In the present contribution, the possibilities and drawbacks of simple sample treatments (i.e., dilution and suspension) in combination with total reflection X-ray fluorescence spectrometry (TXRF) for the analysis of different types of biological samples have been critically evaluated. For that, a set of reference materials or well-characterized biological human fluids (blood, serum, plasma and seminal plasma) and animal/vegetal tissues have been used to estimate the analytical capabilities in terms of limits of detection, trueness and precision of the proposed TXRF methods. The results are based on the authors' experience in analysing biological samples using TXRF, and it is expected that they can be useful for new TXRF users in this field and they can provide a good basis for further application of this technique in clinical studies and other applications dealing with the analysis of biological samples in the future.     

Spectrophotometric Determination of Ammonia in Estuarine Waters by Hybrid Reagent‐Injection Gas‐Diffusion Flow Analysis

Abstract

A flow‐injection gas‐diffusion technique is described for the online determination of ammonia in estuarine waters covering a salinity range of S=0 to 36. The flow analysis system, which is a hybrid of reagent injection and conventional sample‐injection flow systems, avoids the need for a rotary injection valve. Whereas gas‐diffusion techniques have been widely applied in conventional sample‐injection flow analysis, reagent‐injection flow analysis involving gas diffusion has been little used because it is susceptible to interference from dissolved gaseous species such as carbon dioxide coexisting with ammonia in the sample. This source of interference has been overcome by online adjustment of sample to pH 8.4 prior to the injection of the base that initiates gas diffusion of ammonia. The pore sizes of hydrophobic membranes used in gas diffusion were characterized by a bubble‐point test prior to use in the flow analysis system. These showed wide variation in pore size, and grading and careful selection was necessary in order to obtain reliable gas diffusion measurements of ammonia. The proposed flow‐injection system can be operated in a continuous flow mode, at a sample throughput of 135 measurements hr^?1 with a typical limit of detection (LOD) of 9 µg N L^?1, or in stopped‐flow mode at 60 measurements hr^?1 with a LOD of 3 µg N L^?1. The technique was validated using water samples containing a wide range of dissolved carbon dioxide concentrations, salinity, and pH. Excellent agreement (r=0.999) was observed between results obtained using the reagent‐injection system and an approved reference method.     

Laser fluorescence on radio-active isotopes produced in very low yield

East particle-photon coincidence techniques, developed at Daresbury with strontium isotopes, allow ultrasensitive laser fluorescence spectroscopy of beams of radio-active isotopes which can only be produced in very low yields. The technique has now been applied to neutron-deficient barium isotopes down to¹²⁰Ba. From measured hyperfine splittings and isotope shifts, nuclear moments and changes in mean square radii have been determined. The work has revealed an abrupt increase in the mean square radius for¹²¹Ba large enough to disrupt the systematic staggering of nuclear size seen for the series. In a recent experiment an isomeric state of¹²⁷Ba with a half-life of about 2 seconds has been produced in a very low yield; nevertheless we have succeeded in obtaining a fluorescence spectrum.     

Isotope studies of hydrogen and oxygen in ground ice-experiences with the equilibration technique

Equilibration technique suitable for a large amount of samples is described for hydrogen and oxygen isotope analyses of ground ice, especially ice wedges, including the sampling strategy and the analytical procedure as well as the calibration of the Finnigan MAT Delta-S mass spectrometer in June, 1999. Since for future analyses of ice wedges, a higher sampling resolution with limited sample volume is required, the limit of the equilibration technique for small water sample sizes of between 0.05 and 5 ml was checked. For water samples smaller than 1 ml, corresponding to a molar ratio [H2O]/[H2] of smaller than 0.994, a balance correction has to be applied. The experimental errors due to partial evaporation during evacuation, the balance calculation of the isotope equilibration process, the linearity as well as memory effects of the mass spectrometer for samples with large differences in delta18O and deltaD are tackled in this paper. In the polar regions of Northern Siberia without Late Pleistocene and Holocene glaciation, ground ice is used as an archive for paleoclimate studies. First results of stable isotope measurements on ice wedges clearly show a shift towards heavier isotopes and thus warmer winter temperatures as well as a change in the source of the precipitation between Late Pleistocene and Holocene. These results indicate the high potential of ground ice for paleoclimate studies.     

Nuclear orientation at isolde/cern

A facility for Nuclear Implantation into Cold On-Line Equipment (NICOLE) is being installed at the new on-line isotope separator ISOLDE 3 at CERN. The first on-line run was in the beginning of July 1988. The low temperature equipment has been successfully tested and first off-line experiments on various isotopes have been performed. NMR/ON has been done on vaious isotopes (Co, Xe, Pt, Au) in iron host. First experience with the top-loading dilution refrigertor (Oxford Instruments Limited) shows that it performs very well. The cooling power is 400 μW at 100 mK and 34 μW at 25 mK. The base temperature can be kept continuously well below 5 mK. NMR/ON can be performed at temperatures below 5.5 mK. The base temperature on-line is expected to be lower then 6 mK. The sample can be cooled down from room temperature to 10 mK within two hours, to 6 mK within 3 hours which is not only important for off-line but also for on-line experiments when samples have to be changed to remove long lived daughter activity. The latest results will be reported.     

A modified electron bombardment type ion source for the study of solids

A modified electron bombardment type ion source suitable for use with mass spectrometer is described. Ion formation occurs throughout a relatively large volume in the ionisation box, since no magnetic field is used to collimate the ionising electrons. A sensitivity of 2 × 10⁻⁵ amp/torr is obtained for an ion extraction energy of 2 keV and 200 mass resolution. Trajectory tracing has been used to study the operation of the ion source. Capability of the ion source to analyse solid samples in microgram quantity was tested by studying evaporation of BaO from tungsten.     

Resonance ionisation mass spectrometry of krypton and its applications in planetary science

A new resonance ionisation time-of-flight mass spectrometer for determining krypton isotope ratios in extraterrestrial samples is presented. Laser heating is used to extract gas from mg-size samples. A cryogenic sample concentrator is employed. Atoms continuously condense on a 75 K stainless steel substrate at the back plate of a Wiley-McLaren laser ion source from where they are desorbed by a pulsed 1064 nm laser and resonantly ionized in the plume. A three-colour (116.5 nm, 558.1 nm and 1064 nm) excitation scheme is used. Tuneable coherent Vacuum Ultraviolet (vuv) radiation near 116.5 nm is generated by four-wave sum frequency mixing of 252.5 nm and 1507 nm pulsed dye laser beams in a binary mixture of negatively and positively dispersive gases (Xe and Ar). Isotope effects have been observed that reduce the reproducibility of isotope ratio measurements between odd-mass, non-zero nuclear spin isotopes and even-mass, zero nuclear spin isotopes. This can be minimised and stabilised by controlling the laser fluences, experimental geometry, and the population of the magnetic sub-levels of the excited atomic states used in the ionisation process. Once stability is achieved, sample-standard bracketing (during which the known isotope ratios of a standard are determined before and after the measurements of the sample under the same conditions) allows precision and reproducibility of $\sim $ 1 % for the major isotope ratios to be achieved in samples $\sim 10^{6}$ krypton atoms. Detection limits of $<1000$ atoms/isotope have been demonstrated, ratios of $^{81}$ Kr in meteorites have been made with $\sim $ 5–10 % precision. Applications of the instrument in various areas of planetary science are also discussed.     

Investigation of adsorption behaviour of fission products in soils using multitracer technique

The adsorption mechanism of fission products in soils has been investigated by using multitracer technique. The multitracer method used in this work contained fission products as carrier free isotopes which were prepared by neutron irradiation of ²³⁵U at Kyoto University Research Reactor. After the soil sample was mixed into the multitracer solution for two weeks, the solution was separated from soil sample. The gamma-ray spectrometry was carried out for the separated solution and the original multitracer solution which has not been mixed with soils. Distribution coefficients of fission products for soil samples were estimated by measured photoelectric peaks. In this work, distribution coefficients of ten elements for thirty typical Japanese soils were observed.     

Synthesis growth and optical properties of semi organic non linear optical single crystal

A new and efficient semi organic nonlinear optical crystal from the amino acid family has been grown by slow evaporation technique from aqueous solution. The crystals structures were solved by direct methods using SIR92 (WINGX) and refined by a full matrix least-square method using SHELXL97. All this compounds crystallized in noncentrosymetric groups. Second harmonic generation measurements were performed by applying the Kurtz and Perry model, to powder samples of compounds at 1,064 nm.     

A comparison of different radiochemical methods applicable for the determination of plutonium isotopes in urine via alpha spectrometry

Measurement of plutonium isotopes in vivo is not feasible for radiation protection purposes. Considering the slow rate of plutonium excretion, the respect to annual dose limits, whenever risk of plutonium internal contamination occurs, implies the need of a monitoring programme based on very sensitive bioassay, i.e., measurement of plutonium content in samples of urine or feces, characterized by a very low minimum detectable activity. Alpha spectrometry is the most common measurement method applied in this field. The applicability of this method strictly depends on the procedure adopted for the sample radiochemical preparation preceding the real spectrometric counting and, particularly, on the element chemical recovery that is one of the parameters that mostly influence the minimum detectable activity achievable by the analysis. The aim of the present work is to compare the performances of four of the most widely adopted radiochemical procedures making use of different separation methods for the determination of plutonium in urine samples via alpha spectrometry.     

Rapid speciation and quantification of selenium compounds by HPLC-ICP MS using multiple standards labelled with different isotopes

Speciation analysis using high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICP MS) is now commonly used to investigate metabolic and toxicological aspects of some metals and metalloids. We have developed a rapid method for simultaneous identification and quantification of metabolites of selenium (Se) compounds using multiple standards labelled with different isotopes. A mixture of the labelled standards was spiked in a selenised garlic extract and the sample was subjected to speciation analysis by HPLC-ICP MS. The selenised garlic contains γ-glutamyl-methylselenocysteine, methylselenocysteine, and selenomethionine and the concentrations of those Se compounds were 723.8, 414.8, and 310.7 ng Se ml^?1, respectively. The isotopically labelled standards were also applied to the speciation of Se in rat urine. Selenate, methylselenonic acid, selenosugar, and trimethyselenium ions were found to be excreted by the present speciation procedure. Multiple standards labelled with different stable isotopes enable high-throughput identification and quantitative measurements of Se metabolites.     

Flowing and Nonflowing Liquid Electrode Discharge Microplasma for Metal Ion Detection by Optical Emission Spectrometry

Abstract

Liquid electrode discharge microplasma offers a simple, portable, and small platform for fast spectrochemical determination of metal ions in solution samples with lower consumption of consumables (e.g., working gases, electric current, and cooling water). Various liquid electrode discharge devices for metal ions determination with optical emission spectrometry have been developed in the past 20 years. We aim here to provide an overview of this field and to show the similarities and differences, and strengths and weaknesses of different flowing liquid electrode discharge systems and nonflowing liquid electrode discharge systems. We also discuss sample flow rates in flowing systems, required sample volume in nonflowing systems, and the two systems’ applications to real complex samples in this review.     

Application of stable isotopes and hydrochemical analysis in groundwater aquifers of Argolis Peninsula (Greece)

The present study examines the isotopic and hydrochemical composition of 18 inland spring waters and 3 coastal karstic spring waters, covering the period between October 2005 and March 2008. The stable isotopes (¹⁸O, ²H) processing has revealed the absence of significant evaporation phenomena and that the origin of fresh water samples is meteoric. Using ¹⁸O values in rainfall waters, an average line of isotopic depletion with altitude has been constructed, extracting a rate of?0.45‰/100 m as typical for the study area. Furthermore, the mean altitude of recharge of the springs has been estimated by plotting the groundwater sampling points on a δ¹⁸O versus altitude diagram. Hydrochemistry results have shown that the dissolution of carbonate, flysch and ophiolitic formations defines the hydrochemical characteristics of groundwater. Moreover, seawater intrusion in the coastal area is significantly high, causing the water in the three karstic springs to be brackish.