Solvent extraction studies using tetracycline as a complexing agent. XIII. Application of tetracycline for separation of interfering elements in activation analysis of uranium

Tetracycline in solution of benzyl alcohol was used as an extracting agent to separate uranium from interfering elements in the determination of uranium and of isotopic ratio²³⁵U/²³⁸U by neutron activation analysis. Separation gives a recovery of 97% for uranium and the interferences from matrices of pitchblende and monazite are eliminated.From a dissertation submitted by R. Petrauskas to the University of São Paulo in partial fulfilment for a Master of Science Degree in Nuclear Technology.     

Concentrations of Fe, Cu and Zn in rum by EDXRF using APDC preconcentration

Ten rum (aguardente) samples commercialized in Piracicaba region, São Paulo State, Brazil Southeast, were analysed by energy-dispersive X-ray fluorescence (EDXRF) using ammonium pyrrolidinedithiocarbamate (APDC) preconcentration in order to determine Fe, Cu and Zn concentrations. The effect of sucrose (2%) was also studied in this methodology, using a multielemental standard solution (40% ethanol). Copper concentrations in two samples were higher than the value allowed by Brazilian law. Limits of detection for these elements were in the ng^.ml^-1 range.     

Determination of trace elements in tree rings ofPinus by neutron activation analysis

The elemental composition of pine trees as a function of age was achieved by the tree-ring method. By using instrumental neutron activation analysis, trace elements were determined in individual rings ofPinus elliottii var.elliottii of 32, 14 and 9 years, from an implanted forest ofPinus sp., Buri, São Paulo, far away from industrial pollution. Different components of the system such as needles, pith, bark, soil and litter were also analyzed for 18 elements (As, Br, Ce, Co, Cs, Eu, Fe, Hf, K, La, Mn, Na, Rb, Sc, Sm, Yb, Zn, and Zr). Al, B, Ba, Ca, Fe, K, Mg, and P concentrations were determined by atomic absorption and/or emission spectrometry (AAS; ICP-AES). Some elements have showed similar radial distribution of the concentration for the three ages. Abrupt concentration changes in the pith and ring-bark boundary corresponding to the first and last growth rings were observed.     

The use of Tillandsia usneoides L. as bioindicator of air pollution in São Paulo, Brazil

Epiphytic bromeliadTillandsia usneoides was used as a biomonitor of metal atmospheric pollution in the city of São Paulo, Brazil. The samples were collected from an unpolluted area and were exposed for 8 weeks in 10 sites of the city and in a control site. The data obtained showed that the control site presented lower concentration for most elements analyzed and the highest concentrations of Na, Cl, Br, K. The highest concentrations of Zn, Cu and V were observed in stations submitted to industrial and vehicular sources. The results obtained for rare earth elements, Al, Fe, Mg, Mn, Rb and Sc indicate mineral dust origin. The elements Ba, As and Sb presented higher values in stations near streets with heavy traffic.     

An evaluation of the delayed neutron counting method for simultaneous analysis of uranium and thorium and for235U/238U isotopic ratio determination

This paper describes an evaluation of activation analysis by delayed neutron counting to determine uranium and thorium simultaneously in geological materials and to measure²³⁵U/²³⁸U isotopic ratios. A procedure to isolate the thorium before the irradiation was studied and adapted for use when the interference of uranium makes the nondestructive thorium analysis impossible.²³⁵U/²³⁸U ratios were determined in standards with²³⁵U abundances from about 0.5 to 93%, in milligram size samples. Discussion on precision, accuracy and total error of the method is presented.From a thesis submitted by M. J. A. ARMELIN to the University of São Paulo in partial fulfillment of the requirements for a Doctor of Science Degree in Nuclear Technology.     

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.     

Determination of heavy metals and other trace elements in lake sediments from a sewage treatment plant by neutron activation analysis

Instrumental neutron activation analysis (INAA) was used to determine metals (Ba, Co, Cr, Cs, Fe, Hf, Rb, Sc, Zn), semi-metals (As, Sb), actinides (U, Th) and rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in bottom sediments from one of the ponds of the Sewage Treatment Plant (STP) in São Paulo, Brazil. The results obtained were compared with the concentration determined in a soil profile and in a rock sample, in natura, representing the lithologies of the region, and indicated that only As, Cr and Zn can have their origin associated with the residues disposed around the pond.     

Application of the radioreagent method for trace determination of lead

A radioreagent method of analysis was developed and applied to the determination of trace quantities of lead in several types of samples. The method is based on the extraction of radioactive cobalt, displaced by lead from the cobalt chelate of ethylenediaminetetraacetate labelled with⁶⁰Co, into a tetracycline-benzyl alcohol solution. The radioactivity of the released cobalt, extracted into the organic phase, is proportional to the lead concentration. Interference caused by some elements was eliminated by means of a previous separation of lead using dithizone. The method was applied for lead determination in aerosol samples, gasoline and samples from the International Atomic Energy Agency, namely: simulated-air filter (Air-3), fresh water (W-3), dried animal whole blood (A-2) and calcined animal bone (A-3/1). The sensitivity, accuracy and precision of the method were also studied.Part of this material was submitted to the University of São Paulo in partial fulfilment for a Doctor of Science's Degree of A. M. G. FIGUEIREDO.     

Influence of intersite modes on the exchange interaction in electron transfer at large distances

We consider the dependence of the exchange interaction in electron transfer processes on the intersite vibrational modes. We assume, in particular, that high-frequency intramolecular modes of proteins may play this role in biological processes. We compare our model with that for tunneling through a time dependent barrier and with other works which considered the dependence of the exchange interaction on the nuclear coordinates.Work partially supported by the Brazilian Agency CNPq and by the NSF (Grant PCM-8406049)On leave of absence from Institute de Física e Química de São Carlos, Universidade de São Paulo, 13560, São Carlos, SP, BrazilOn leave of absence from Departamento de Física, Universidade Federal de Pernambuco, 50000, Recife, Pe, BrazilContribution No. 7325     

Recoil spectrometer for the detection of single atoms

Kinetic decay of paramagnetic species formed in the radiolysis of tetracycline hydrochloride in powder form, at 77 K, shows that most of the H· is not able to migrate. Geminate recombination between H· and its partner is the main reaction: H·+TC· TCH, although a few H· succeed in diffusing slowly. But when H· acquires enough kinetic energy to migrate, it reacts preferentially with species different from its partner. The e^– is not observed by ESR, at 77 K, although tetracycline hydrochloride is a chemical trap for e^– in methanol, benzyl alcohol and alkaline aqueous solutions. In the radiolysis of tetracycline hydrochloride in powder form, the dimethylammonium group blocks H· abstraction reaction at 77 K.From a thesis submitted by S. M. L. G. to the University of São Paulo in partial fulfillment of the requirements for a Doctor of Science in Nuclear Technology.     

Trace elements in a profile of the unsaturated zone of the São Paulo Basin

This study comprises Tertiary sediments (clays, silts, and fine clayey sands) from the unsaturated zone of the Experimental Station in the University of São Paulo, taken from a nine meters depth profile; ten samples were separated in bulk and <53 m fractions. Chemical composition was determined by INAA to ascertain the distribution of trace elements throughout the sediment deposition, and to establish the background parameters, useful for mobilization studies of such elements after industrial waste disposal.     

Analysis of Tradescantia pallida plant exposed in different sites for biomonitoring purposes

Comparisons were made between the results obtained for elements accumulated by Tradescantia pallidaplant exposed in sites with different pollution levels: Cerqueira César and Congonhas districts, considered polluted areas of São Paulo city, and Caucaia do Alto county, considered a non polluted site. Statistical test applied to the results indicated that plant samples from polluted areas presented higher concentrations of Ba, Ce, Cr, Co, Fe, La, Sb and Sc than those found for ones from a non-polluted site. Discriminant analysis applied to the results obtained revealed three groups of results corresponding to sites with different levels of pollution.     

Evaluation of zirconium as a permanent chemical modifier using synchrotron radiation and imaging techniques for lithium determination in sediment slurry samples by ET AAS

In the present paper, lithium was determined in river sediment using slurry sampling and electrothermal atomic absorption spectrometry (ET AAS) after L’vov platform coating with zirconium (as a permanent chemical modifier). The performance of this modifier and its distribution on the L’vov platform after different heating cycles were evaluated using synchrotron radiation X-ray fluorescence (SRXRF) and imaging scanning electron microscopy (SEM) techniques. The analytical conditions for lithium determination in river sediment slurries were also investigated and the best conditions were obtained employing 1300 and 2300 °C for pyrolysis and atomization temperatures, respectively. In addition, 100 mg of sediment samples were prepared using 4.0 mol l⁻¹ HNO₃. The Zr-coating permitted lithium determination with good precision and accuracy after 480 heating cycles using the same platform for slurry samples. The sediment samples were collected from five different points of the Cachoeira river, São Paulo, Brazil. The detection and quantification limits were, respectively, 0.07 and 0.23 μg l⁻¹.     

Screening Brazilian commercial gasoline quality by hydrogen nuclear magnetic resonance spectroscopic fingerprintings and pattern-recognition multivariate chemometric analysis

The identification of gasoline adulteration by organic solvents is not an easy task, because compounds that constitute the solvents are already in gasoline composition. In this work, the combination of Hydrogen Nuclear Magnetic Resonance (¹H NMR) spectroscopic fingerprintings with pattern-recognition multivariate Soft Independent Modeling of Class Analogy (SIMCA) chemometric analysis provides an original and alternative approach to screening Brazilian commercial gasoline quality in a Monitoring Program for Quality Control of Automotive Fuels. SIMCA was performed on spectroscopic fingerprints to classify the quality of representative commercial gasoline samples selected by Hierarchical Cluster Analysis (HCA) and collected over a 6-month period from different gas stations in the São Paulo state, Brazil. Following optimized the ¹H NMR-SIMCA algorithm, it was possible to correctly classify 92.0% of commercial gasoline samples, which is considered acceptable. The chemometric method is recommended for routine applications in Quality-Control Monitoring Programs, since its measurements are fast and can be easily automated. Also, police laboratories could employ this method for rapid screening analysis to discourage adulteration practices.     

Assessing selected estrogens and xenoestrogens in Brazilian surface waters by liquid chromatography-tandem mass spectrometry

A sensitive and specific method was developed and validated for the determination of estrogen and xenoestrogen in surface waters using liquid chromatography followed by tandem mass spectrometry. Chromatographic separation was performed using ammonium hydroxide solutions in water and in methanol as mobile phase. Compounds were determined in a triple quadrupole mass spectrometer equipped with an electrospray ionization interface operating in the negative mode. Multiple reaction monitoring conditions were optimized for estrone, 17β-estradiol, estriol, 17α-ethinylestradiol, bisphenol A, 4-n-octylphenol, and 4-n-nonylphenol. The method was linear from 0.1 ng L^− 1 to 10 µgL^− 1. Limits of quantification varied between 0.1 and 3.1 ng L^− 1 and recoveries for a 50 ng L^− 1 spiked-surface water solution varied between 72 and 140%. The method was successfully used to determine estrogen and xenoestrogen levels in Brazilian water samples collected along the Atibaia River Basin, in the State of São Paulo. Concentrations of estrogens varied from 2.2 to 39 ng L^− 1. Bisphenol A was the most frequently detected compound as well as the only xenoestrogen in the samples with concentrations between 25 and 84 ng L^− 1.     

Solvent extraction studies using tetracycline as complexing agent

The behaviour of tetracycline as an extracting agent for strontium, iodine, barium, molybdenum, technetium, zirconium, niobium, cesium, ruthenium, tellurium and uranium has been studied and the influence of the acidity of the aqueous phase upon extraction of the elements mentioned has been examined. Experiments have been made to determine whether or not the species extracted into the organic phase is the complex formed between tetracycline and the elements considered as well as to determine the time of shaking necessary so that the equilibrium between the phases is attained. As a practical application, the possibility of using the tetracycline-benzyl alcohol system for separating the fission products¹³⁷Cs,¹⁴⁰Ba,¹⁴⁰La,¹⁴¹Ce,¹⁰³Ru,⁹⁵Zr and⁹⁵Nb from each other and from uranium is presented. The same study has been made for¹³¹I,^99mTc,⁹⁹Mo,¹³²Te,²³⁹Np and uranium and the steps necessary for the separation of these elements are proposed.From a thesis submitted by I. I. L. CUNHA to the Instituto de Pesquisas Energéticas e Nucleares-University of São Paulo in partial fulfillment of the requirements for a Doctor of Science's Degree. Work supported by Comissão Nacional de Energia Nuclear.     

Radiochemical separation of thorium by isotope ion exchange

The aim of the present work is to obtain the separation of²³³Th from the radioisotopes formed in the irradiation of Mn, U, Ba, Cs, Co and the lanthanide elements with thermal neutrons, because they may interfere in the neutron activation analysis of Th, when the activity of²³³Th is used. The experiments were performed with the resin Bio-Rad AG 50W X-4 and X-8 (100–200 mesh) in the thorium form. The separation of²³³Th from the interfering radioisotopes is based on the retention of²³³Th by the resin (isotope exchange) and the elution of the interfering radioisotopes with a dilute solution of Th in 0.5M HCl. Batch experiments were made in order to determine the equilibrium time for the isotopic ion exchange of thorium and also the distribution coefficients of the interfering elements between the solution and the resin. Column experiments were carried out with the purpose of establishing the conditions that allow the maximum isotope exchange of²³³Th and the minimum retention of the interfering radioisotopes in the resin. With this purpose, a statistical interpretation of a four variable experimental design is presented.From a thesis submitted by C. Sepúlveda Munita to the Instituto de Pesquisas Energéticas e Nucleares (CNEN/SP) University of São Paulo, in partial fulfillment of a Doctor of Science's Degree. Work supported by the Brazilian Atomic Energy Commission.     

Chemical Characterization by INAA of Brazilian Ceramics and Cultural Implications

Archaeological ceramic fragments from Água Limpa site, in São Paulo, Brazil, were analyzed using instrumental neutron activation analysis. Multivariate statistical methods including Pearson correlation coefficient, cluster and principal components analysis were used to interpret the concentration data. Rare earth and alkaline elements were highly correlated. Six principal components explained 74.9% of the total variance and five clusters were found. The sample chemical composition showed that all samples have the same provenance.     

Limestone doses affecting mineral contents in tropical grass forage

Summary Field trial was performed at the experimental farm of Southeast Embrapa Cattle, São Carlos - SP, Brazil, on a 16 year old Brachiaria decumbens pasture, grown on a distrophic Hapludox (Oxisol), recovered by the use of limestone and fertilizer. The experiments were carried out in random blocks, with 6 replications and 5 treatments. The 100 m² blocks were established in the pasture. Each block received a sequence of limestone doses of 0, 1, 2, 4 and 8 t/ha. The forage samples were taken one year after limestone application on soil surface. Instrumental neutron activation analysis (INAA) followed by gamma-ray spectrometry was the analytical method used to determine mineral contents. The statistical analysis showed a negative linear correlation of Br, Co, Cr, Mn and Zn contents in forage with the limestone doses, while the uptake of Mg was affected in a positive way.