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Abstract  

Phosphorus is an essential element for plants and animals, playing a fundamental role in the production of biochemical energy. Despite its relevance, phosphorus is not commonly determined by instrumental neutron activation analysis (INAA), because 32P does not emit gamma-rays in its decay. There are alternative methods for the determination of phosphorus by INAA, such as the use of beta counting or the measurement of bremsstrahlung originated from the high energy beta particle from 32P. Here the determination of phosphorus in plant materials by measuring the bremsstrahlung production was further investigated, to optimize an analytical protocol for minimizing interferences and overcoming the poor specificity. Eight certified reference materials of plant matrices with phosphorus ranging between 171 and 5,180 mg kg−1 were irradiated at a thermal neutron flux of 9.5 × 1012 cm−2 s−1 and measured with a HPGe detector at decay times varying from 7 to 60 days. Phosphorus solutions added to a certified reference material at three levels were used for calibration. Counts accumulated in the baseline at four different regions of the gamma-ray spectra were tested for the determination of phosphorus, with better results for the 100 keV region. The Compton scattering contribution in the selected range was discounted using an experimental peak-to-Compton factor and the net areas of all peaks in the spectra with energies higher than 218 keV, i.e. Compton edge above 100 keV. Amongst the interferences investigated, the production of 32P from sulfur, and the contribution of Compton scattering should be considered for producing good results.

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Abstract  

Brazil holds the second largest population of domestic dogs in the world, with 33 million dogs, only behind the United States. The annual consumption of dog food in the country is 1.75 million tons, corresponding to the World’s sixth in trade turnover. Dog food is supposed to be a complete and balanced diet, formulated with high quality ingredients. All nutrients and minerals required for an adequate nutrition of dogs are added to the formulation to ensure longevity and welfare. In this context, the present study aimed at assessing the chemical composition of dry dog foods commercialized in Brazil. Thirty-four samples were acquired in the local market of Piracicaba and analyzed by instrumental neutron activation analysis (INAA) to determine the elements As, Br, Ca, Co, Cr, Cs, Fe, K, La, Na, Rb, Sb, Sc, Se, U, and Zn. In general, the concentrations of Ca, Fe, K, Na, and Zn complied with the values required by the Association of American Feed Control Officials (AAFCO). To evaluate the safety of dog food commercialized in Brazil, further investigation is necessary to better understand the presence of toxic elements found in this study, i.e. Sb and U. INAA was useful for the screening analysis of different types and brands of dry dog foods for the determination of both essential and toxic elements.

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Abstract  

The availability of chemical elements for plants is mainly dependent on the nature of the soil and characteristics of each species. The transfer factors of lanthanides from the soil to the tree leaves of the Atlantic Forest, Brazil, were calculated for one fern species (Alsophila sternbergii—Pteridophyta division) and four magnoliophytes species (Bathysa australis, Euterpe edulis, Garcinia gardneriana and Guapira opposita—Magnoliophyta division) obtained in two areas of Serra do Mar State Park and collected in two different seasons. Samples were analyzed by instrumental neutron activation analysis (INAA). The soil-to-plant transfer factor (TF = Cplant:Csoil) in magnoliophytes species was correlated to the mass fraction of lanthanides in the soil, described by a exponential model (TF = a.Csoil −b). Despite the tree fern Alsophila sternbergii presented a hyperaccumulation of lanthanides, this species did not have a significant relationship between TF and mass fraction in soil. Results indicated that plants of Magnoliophyta division selected the input of lanthanides from the soil, while the same was not observed in Alsophila sternbergii.

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Abstract  

Soil as an impurity in sugarcane is a serious problem for the ethanol industry, increasing production and maintenance costs and reducing the productivity. Fe, Hf, Sc and Th determined by INAA were used as tracers to assess the amount of soil in sugarcane from truckloads as well as in the juice extraction process. Quality control tools were applied to results identifying the need for stratification according to soil type and moisture. Soil levels of truckloads had high variability indicating potential for improving cut and loading operations. Samples from the juice extraction process allowed tracking the soil in the mill tandem.

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Abstract  

For environmental quality assessment, INAA has been applied for determining chemical elements in small (200 mg) and large (200 g) samples of leaves from 200 trees. By applying the Ingamells’ constant, the expected percent standard deviation was estimated in 0.9–2.2% for 200 mg samples. Otherwise, for composite samples (200 g), expected standard deviation varied from 0.5 to 10% in spite of analytical uncertainties ranging from 2 to 30%. Results thereby suggested the expression of the degree of representativeness as a source of uncertainty, contributing for increasing of the reliability of environmental studies mainly in the case of composite samples.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Luís dos Santos
,
Márcio Bacchi
,
Elisabete De Nadai Fernandes
, and
Simone da Silva Cofani dos Santos

Abstract  

As a non-destructive and multi-element technique, with high-level metrological properties, instrumental neutron activation analysis (INAA) has an important role to determine chemical elements in food. However, its use may be limited when looking for mass fractions near the detection limits. The Compton scattering of higher energy gamma-rays raised the spectrum baseline thus impairing the determination of several elements. Therefore, the gamma-ray spectrometry with Compton suppression becomes an alternative for improving the performance of INAA, since it can reduce the uncertainty of measurements and the detection limits by increasing the proportion between photopeak area and baseline. Here the performance of a Compton suppression system set by Ortec, with 50% relative efficiency and 2.04 keV resolution (FWHM) for the 1,332 keV photopeak, was evaluated for food analysis. Samples of beans, chickpeas, lentils, peas, and rice were irradiated with neutrons and measured in the suppression system. Detection limits calculated from suppressed and unsuppressed spectra were compared. The suppression factor achieved by the system for 137Cs was 5.88 ± 0.11 (n = 20) in the plateau region (358 to 382 keV), which was stable along a 20 week period and similar to the data provided in literature for other systems. Amongst fifteen elements determined, the detection limits for Br, Co, La, Na, Sc, and Se were not improved by the use of Compton suppression. On the other hand, the variable improvement obtained for As, Ca, Cd, Cr, Fe, Hg, K, Rb, and Zn corroborated the idea that the performance of the Compton suppressor must be individually assessed for each type of sample.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Luís dos Santos
,
Elisabete De Nadai Fernandes
,
Márcio Bacchi
,
Gabriel Sarriés
,
Lucimara Blumer
, and
Fernando Júnior

Abstract  

Aiming at international competitiveness of the Brazilian dairy sector, new governmental policies were released to improve quality and safety of bovine milk. In this context, it is important to quantify essential and toxic chemical elements. Here, the composition of milk samples taken at 32 dairy farms in Minas Gerais State was assessed by instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS), besides the evaluation of usual quality parameters. Significant differences were found for Ba, K, Na and fat content amongst dairy farms with diverse quality levels established on basis of somatic cell and total bacterial count.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Luís dos Santos
,
Elisabete De Nadai Fernandes
,
Márcio Bacchi
,
Gabriel Sarriés
,
Lucimara Blumer
, and
Fernando Barbosa

Abstract  

The bovine dairy cattle demand diets of high nutritional value being essential to know chemical composition of feed supplied to cows to achieve high levels of quality, safety and productivity of milk. Different roughages and concentrates from Minas Gerais and Rio Grande do Sul states, Brazil, were analyzed by instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS). Concentrate and roughage samples were differentiated by mass fractions of As, Ba, Mg, P, Rb and Sr. Samples of concentrate from both origins were differentiated by mass fractions of As, Cd, Co, Cr, Cs, Ni and Rb.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Felipe Fonseca
,
Elisabete De Nadai Fernandes
,
Vanessa Rodrigues
,
Isabel de Oliveira Cavalca
,
Leandro Camilli
,
Claudiney Bardini
, and
Elvis De França

Abstract  

The quality of environmental studies depends on the utilization of adequate sampling protocol and analytical method for obtaining reliable results and minimizing analytical uncertainties. In order to demonstrate the applicability of INAA for determining chemical element composition of invertebrates, this work evaluated sample representativeness in terms of subsampling and sample size. Br, Co, Fe, K, Na, Sc and Zn could be determined in very small samples despite increasing of analytical uncertainties. Special attention should be directed to invertebrate species with small structures because of the high chemical variation observed among different sample sizes tested.

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