Analytical procedure based on slurry sampling for determining selenium in organic vegetable samples by graphite furnace atomic absorption spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aquatic insects as the main food resource of fish the community in a Neotropical reservoir

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Can seasonal differences influence food web structure on preserved habitats? Responses from two Brazilian streams

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Food bodies in Cissus verticillata (Vitaceae): ontogenesis, structure and functional aspects

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Food resource utilization of the skates Rioraja agassizii (Müller & Henle, 1841) and Psammobatis extenta (Garman, 1913) on the continental shelf off Ubatuba, South-eastern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sources of errors in the quantitative analysis of food carotenoids by HPLC

Several factors render carotenoid determination inherently difficult. Thus, in spite of advances in analytical instrumentation, discrepancies in quantitative results on carotenoids can be encountered in the international literature. A good part of the errors comes from the pre-chromatographic steps such as sampling scheme that does not yield samples representative of the food lots under investigation; sample preparation which does not maintain representativity and guarantee homogeneity of the analytical sample; incomplete extraction; physical losses of carotenoids during the various steps, especially during partition or washing and by adsorption to glass walls of containers; isomerization and oxidation of carotenoids during analysis. on the otherhand, although currently considered the method of choice for carotenoids, high performance liquid chromatography (HPLC) is subject to various sources of errors, such as: incompatibility of the injection solvent and the mobile phase, resulting in distorted or split peaks; erroneous identification; unavailability, impurity and instability of carotenoid standards; quantification of highly overlapping peaks; low recovery from the HPLC column; errors in the preparation of standard solutions and in the calibration procedure; calculation errors. Illustrations of the possible errors in the quantification of carotenoids by HPLC are presented.

Jaguarundi (Puma yagouaroundi) (Geoffroy, 1803) (Carnivora, Felidae) food habits in a mosaic of Atlantic Rainforest and eucalypt plantations of southeastern Brazil

A dieta de uma população de jaguarundi (Puma yagouaroundi) (Geoffroy, 1803) (Carnivora, Felidae) foi estudada entre novembro de 2000 e novembro de 2001, em 24,9 km² de mosaico de Mata Atlântica secundária e reflorestamento de eucalipto na Serra de Paranapiacaba, São Paulo, Brasil. A análise das 26 amostras fecais e regurgitadas, obtidas em 570.1 km de percurso, indicou o consumo de 19 itens alimentares em um total de 74 ocorrências de presas. Pequenos mamíferos foram os itens mais frequentemente encontrados na dieta (42,5%), seguidos por aves (21%), répteis (14%) e mamíferos de tamanho médio (3%). A porcentagem de ocorrência (PO) sugere que a dieta concentra-se, principalmente, em pequenos roedores (30%) e aves (21%). Foi também registrada a predação sobre serpentes da família Viperidae. A amplitude de nicho alimentar padronizada (Bsta = 0,76) mostra uma dieta generalista, entretanto, os dados sugerem que o jaguarundi consome principalmente pequenos vertebrados (mamíferos, aves ou répteis), sobretudo, espécies terrestres.

Immunoassays for pesticide analysis in environmental and food matrices

Immunochemical methods have increased considerably in the past years, and many examples of small and large scale studies have demonstrated the reliability of the immunotechniques for control and monitoring gf contaminant residues in different kinds of samples. Application of the immunoassay (IA) methods in pesticide residue control is an area with enormous potential for growth. The most extensively studied IA is the enzyme-linked absorbent assay (ELISA), but several other approaches, that include radioimmunoassay and immunoaffinity chromatography, have been also developed recently. In comparison with classical analytical methods, IA methods offer the possibility of highly sensitive, relatively vapid, and cost-effective measurements. This paper introduces the general IAs used until now, focusing on their use in pesticide analysis, and discussing briefly the effects of interferences from solvent residues or matrix components on the IA performance. Numerous immunochemical methods commonly used for pesticide determination in different samples such as food, crop and environmental samples are presented.

2-DEOXYGLUCOSE-INDUCED FOOD-INTAKE BY NILE TILAPIA, OREOCHROMIS-NILOTICUS (L)

The alimentary and glycemic responses to cytoglycopenia were studied in thirty-one Nile tilapia alevins of indeterminate sex and age, measuring on average 10.67 +/- 0.82 cm. The cytoglycopenia was provoked by ip injection of 60 mg/kg 2-deoxy-D-glucose (2-DG, N = 16). The control group (N = 15) was submitted to ip injection of 0.2 ml saline. Blood samples for glucose determination were obtained before and three hours after drug administration by cardiac puncture. Food was then offered ad libitum. One hour later the animals were sacrificed and their stomachs removed. The difference in wet weight between full and empty stomach was utilized to quantify the food intake. Median food intake was 0.3877 g for the fish treated with 2-DG and 0.107 g for the animals injected with saline. This difference was statistically significant by the Mann-Whitney test (P<0.05). The median values of blood glucose levels before drug injection were 46.19 mg/100 ml in the 2-DG-treated fish and 44.54 mg/100 ml in the control group. Three hours after drug administration, the values were 48.64 mg/100 ml in the experimental group and 56.90 mg/100 ml in the control group. The difference between the values of blood glucose before and after the drug was not significant for either group. We conclude that glucoprivation provokes food intake in fish and that the same glucoprivation was not sufficient to provoke hyperglycemia.

Determination of Total Sulfur in Agricultural Samples by High-Resolution Continuum Source Flame Molecular Absorption Spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reliability of carnitine concentrations measured in single postprandial urine samples from dogs

Objective - To evaluate the reliability of urine carnitine concentrations measured in single postprandial samples, compared with carnitine concentrations measured in 24-hour urine samples. Animals - 19 healthy Beagles. Procedure - After emptying the urinary bladder by catheterization, dogs were fed a canned canine maintenance diet. Approximately 8 hours later, urine, plasma, and serum samples were obtained for determination of urinary carnitine fractional excretion and urine carnitine-to-creatinine concentration ratio. Results were compared with 24-hour urinary carnitine excretion rate. Results - Fractional excretion of carnitine and urine carnitine-to-creatinine ratios correlated poorly with 24-hour urinary carnitine excretion. Conclusion - Determination of 24-hour urinary carnitine excretion is recommended to measure urine carnitine concentrations in dogs.

Food and feeding habits of the neotropical river otter Lontra longicaudis (Carnivora, Mustelidae)

A study of the feeding habits of the neotropical river otter, Lontra longicaudis, based on focal analysis was carried out from July 1986 to July 1987. The study was conducted at a dam in the 'Duas Bocas' Biological Reserve near the town of Cariacica, Espirito Santo State, Brazil. This reserve spreads over an area of 2 910 ha, the surface being mainly covered by the Atlantic Rain Forest. In order to identify the fish and other animal remains found in otter fecal samples, these were compared to the homologous structures of identical species living in the dam. The results of 288 samples were expressed in numbers and frequency of occurrence. Fishes were the most important food item, being present in 281 samples (97.2 %). A species of the genus Geophagus was frequently found in spraints, eaten during all months studied and present in 88.9 % of the samples. Astyanax, Pimelodella, Hoplias, Leporinus, Rhamdia, Tilapia and two other unidentified genera were found less frequently. In decreasing order of occurrence, crustaceans, amphibia, mammals, insects and birds were also encountered. Seasonal variation was verified in the scats between the dry and rainy seasons, with a higher frequency of food items occurring in the latter. In agreement with other species of otters, fishes also are the most commonly ingested prey. Two characteristics of fishes, greater abundance and easier capture, make them the major prey of otters, implying that otters are opportunistic predators eating whatever is more available.

GFAAS determination of mercury in muscle samples of fish from Amazon, Brazil

In the present study, a simple, rapid and sensitive method was developed for the determination of mercury concentrations in the muscle tissue of fish from the Brazilian Amazon using graphite furnace atomic absorption spectrometry (GFAAS) following acid mineralization of the samples in an ultrasonic cold water bath. Using copper nitrate as a chemical modifier in solution and sodium tungstate as permanent modifier, we were able to attain thermal stabilization of the mercury up to the atomisation temperature of 1600 °C in the GFAAS assay. The calculated limits of detection (LOD) and quantification (LOQ) were 0.014 and 0.047 mg kg-1, respectively. © 2013 Elsevier Ltd. All rights reserved.

New voltammetry-based technique for the determination of tebuthiuron in crystal and brown sugar samples

Sugar is widely consumed worldwide and Brazil is the largest producer, consumer, and exporter of this product. To guarantee proper development and productivity of sugar cane crops, it is necessary to apply large quantities of agrochemicals, especially herbicides and pesticides. The herbicide tebuthiuron (TBH) prevents pre- and post-emergence of infesting weed in sugarcane cultures. Considering that it is important to ensure food safety for the population, this paper proposes a reliable method to analyse TBH in sugar matrixes (brown and crystal) using square wave voltammetry (SWV) and differential pulse voltammetry (DPV) at bare glassy carbon electrode and investigate the electrochemical behavior of this herbicide by cyclic voltammetry (CV). Our results suggest that TBH or the product of its reaction with a supporting electrolyte is oxidized through irreversible transfer of one electron between the analyte and the working electrode, at a potential close to +1.16 V vs. Ag |AgClsat in 0.10 mol L-1 KOH as supporting electrolyte solution. Both DPV and SWV are satisfactory for the quantitative analysis of the analyte. DPV is more sensitive and selective, with detection limits of 0.902, 0.815 and 0.578 mg kg-1, and quantification limits of 0.009, 0.010 and 0.008 mg kg-1 in the absence of the matrix and in the presence of crystal and brown sugar matrix, respectively. Repeatability lay between 0.53 and 13.8%, precision ranged between 4.14 and 15.0%, and recovery remained between 84.2 and 113% in the case of DPV conducted in the absence of matrix and in the presence of the crystal sugar matrix, respectively.

Screening and determination of sulphonamide residues in bovine milk samples using a flow injection system

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)