Determinação de arsênio em amostras da cadeia produtiva de frangos de corte por espectrometria de absorção atômica com forno de grafite

Chicken meat is largely consumed in human nutrition and it is produced in extremely large scale in some countries, including Brazil. In this work graphite furnace atomic absorption spectrometry was used for determination of arsenic in chicken and chicken production-related samples. These samples were digested employing a microwave-assisted procedure in closed vessels using a 7 mol L-1 nitric acid solution plus concentrated hydrogen peroxide. The concentration range of total As determined in chicken production-related samples varied from 1.30 to 29.8 mg kg-1 of As. The detection and quantification limits reached were 0.055 and 0.182 mg kg-1, respectively (n = 15).

Síntese hidrotermal assistida por micro-ondas como metodologia sintética eficiente para obtenção da rede metalorgânica [ZN(BDC)(H2O)2]n

This work presents the optimization of the microwave-assisted hydrothermal synthesis of [Zn(BDC)(H2O)2]n . The reactions were carried out at the fixed temperature of 120 ºC for 10, 20, 30 and 40 min. Pure crystalline [Zn(BDC)(H2O)2]n was obtained in high yield (ca. 90%) with a reaction time of 10 min. The phase obtained and its purity was confirmed by Rietveld refinement, with a final value for Rwp/Rexp equal to 1.48. Increased reaction times (20, 30 and 40 min) favored the formation of unwanted by products, resulting in mixtures of several crystalline phases.

Síntese da fenitoína assistida por micro-ondas: proposta de aula prática para alunos de graduação

Microwave synthesis is considered a breakthrough in the field of chemistry due to its benefits over conventional heating methods. We describe, for the first time, the total synthesis of phenytoin adapted for a microwave reactor, proposed as an experiment for undergraduate courses. When carried out with microwaves, the synthetic route provided phenytoin in 6 min and 30 s, while for conventional heating the total time was 170 min. The experiment also involves rapid identification of compounds by TLC, ¹H NMR, FT-IR and melting points determination.

Cromatografia gasosa-espectrometria de massas e derivatização assistida por micro-ondas na identificação de isômeros de glicose: uma prática para o ensino avançado em análise e caracterização de compostos orgânicos

This work reports a practical case based on the use of microwave-assisted derivatization and GC-MS for the analysis of glucose. Using two different methods for derivatization, one reference compound and the calculated dipole moment, all the isomers of glucose were identified. Identification was corroborated for the assignment of structures using the mass spectra. With this work, students are expected to associate different types of information to solve the complex problem of the analysis of glucose.

Simultaneous determination of Cd and Pb in antibiotics used in sugar-cane fermentation process by GFAAS

A method has been developed for the simultaneous determination of Cd and Pb in antibiotics used in sugar-cane fermentation by GFAAS. The integrated platform of transversely heated graphite atomizer was treated with tungsten to form a coating of tungsten carbide. Six samples of commercial solid antibiotics were analyzed by injecting 20 µL of digested samples into the pretreated graphite platform with co-injection of 5 µL of 1000 mg L-1 Pd as chemical modifier. Samples were mineralized in a closed-vessel microwave-assisted acid-digestion system using nitric acid plus hydrogen peroxide. The pyrolysis and atomization temperatures of the heating program of the atomizer were selected as 600°C and 2200°C, respectively. The calculated characteristic mass for Cd and Pb was 1.6 pg and 42 pg, respectively. Limits of detection (LOD) based on integrated absorbance were 0.02 µg L-1 Cd and 0.7 µg L-1 Pb and the relative standard deviations (n = 10) for Cd and Pb were 5.7% and 8.0%, respectively. The recoveries of Cd and Pb added to the digested samples varied from 91% to 125% (Cd) and 80% to 112% (Pb).

Direct determination of calcium in milk by atomic absorption spectrometry using flow-injection analysis

A flow-injection system with sample and reagent addition by the synchronous merging zones approach for calcium determination in milk by flame AAS is proposed. Main parameters were optimized using a factorial design with central point. The optimum conditions were 2.5% (m/v) for La concentration, 8 mL min-1 for the carrier flow-rate, 20 cm for coiled reactor and 250 ìL for sample volume. Different sample preparation procedures were evaluated such as dilution in water or acid and microwave-assisted decomposition using concentrated or diluted acids. The optimized flow system was applied to determine Ca in eleven commercial milk samples and two standard reference materials diluted in water. Similar calcium levels were encountered comparing the results obtained by the proposed method (dilution in water) with those obtained using microwave-oven digestion. Results obtained in two standard reference materials were in agreement at 95% confidence level with those certified. Recoveries of spiked samples were in the 93% - 116% range. Relative standard deviation (n = 12) was < 5.4% and the sample throughput was 150 measurements per hour, corresponding to a consumption of 250 µL of sample and 6.25 mg La per determination.

Spectrophotometric determination of diclofenac in pharmaceutical preparations assisted by microwave oven

In this work, an effective and low-cost method for the determination of sodium or potassium diclofenac is proposed in its pure form and in their pharmaceutical preparations. The method is based on the reaction between diclofenac and tetrachloro-p-benzoquinone (p-chloranil), in methanol medium. This reaction was accelerated by irradiating of reactional mixture with microwave energy (1100 W) during 27 seconds, producing a charge transfer complex with a maximum absorption at 535 nm. The optimal reaction conditions values such as reagent concentration, heating time and stability of the reaction product were determined. Beer's law is obeyed in a concentration range from of 1.25x10-4 to 2.00x10-3 mol l-1 with a correlation coefficient of 0.9993 and molar absorptivity of 0.49 x10³ l mol-1 cm-1. The limit of detection (LOD) was 1.35x10-5 mol l-1 and the limit of quantification (LOQ) was 4.49x10-5 mol l-1. In the presence of the common excipients, such as glucose, lactose, talc, starch, magnesium stearate, sodium sulphite, titanium dioxide, polyethyleneglycol, polyvinylpirrolidone, mannitol and benzilic alcohol no interferences were observed. The analytical results obtained by applying the proposed method compare very favorably with those given by the United States Pharmacopeia standard procedure. Recoveries of diclofenac from various pharmaceutical preparations were within 95.9% to 103.3%, with standard deviations ranging from 0.2% to 1.8%.

Flavonoid extraction from Alpinia zerumbet (Pers.) Burtt et Smith leaves using different techniques and solvents

The current study aims to verify the best method for a rapid and efficient extraction of flavonoids from Alpinia zerumbet. Dried leaves were extracted using distillated water and ethanol 70% by extraction methods of shaking maceration, ultrasonic, microwave and stirring. By the application of TLC and reversed-phase HPLC techniques the rutin and kaempferol-3-O-glucuronide were detected. Ethanol 70% was more efficient for flavonoids extraction than water. No significant yielding variation was verified for ultrasonic, microwave and stirring methods using ethanol 70% (11 to 14%). The relative concentration of rutin and kaempferol-3-O-glucuronide, respectively, was higher by ultrasonic (1.5 and 5.62 mg g-1 dried leaves, respectively) and by microwave (1.0 and 6.64 mg g-1 dried leaves) methods using ethanol. Rapid and simplified extraction proceeding optimize phytochemical work and acquisition of secondary metabolites.

Flavonoids extraction from Alpinia zerumbet (Pers.) Burtt et Smith leaves using different procedures

The current study aims to verify the best method for a rapid and efficient extraction of flavonoids from Alpinia zerumbet. Dried leaves were extracted using distillated water and ethanol 70% by extraction methods of shaking maceration, ultrasonic, microwave and stirring. By the application of TLC and reversed-phase HPLC techniques the rutin and kaempferol-3-O-glucuronide were detected. Ethanol 70% was more efficient for flavonoids extraction than water. No significant yielding variation was verified for ultrasonic, microwave and stirring methods using ethanol 70% (11 to 14%). Relative concentration of rutin and kaempferol-3-O-glucuronide, respectively, was higher by ultrasonic (1.5 and 5.62 mg g-1 dried leaves) and by microwave (1.0 and 6.64 mg g-1 dried leaves) methods using 70% ethanol. Rapid and simplified extraction proceeding optimize phytochemical work and acquisition of secondary metabolites.

Comparison of two commercial kits and two extraction methods for fecal glucocorticoid analysis in ocelots (Leopardus pardalis) submitted to ACTH challenge

The ocelot (Leopardus pardalis) is included in list of wild felid species protected by CITES and is part of conservation strategies that necessarily involve the use of assisted reproduction techniques, which requires practical and minimally invasive techniques of high reproducibility that permit the study of animal reproductive physiology. The objective of this study was to compare and validate two commercial assays: ImmuChem Double Antibody Corticosterone 125I RIA from ICN Biomedicals, Costa Mesa, CA, USA; and Coat-a-Count Cortisol 125I RIA from DPC, Los Angeles, CA, USA, for assessment of fecal glucocorticoid metabolites in ocelots submitted to ACTH (adrenocorticotropic hormone) challenge. Fecal samples were collected from five ocelots kept at the Brazilian Center of Neotropical Felines, Associação Mata Ciliar, São Paulo, Brazil, and one of the animals was chosen as a negative control. The experiment was conducted over a period of 9 days. On day 0, a total dose of 100 IU ACTH was administered intramuscularly. Immediately after collection the samples were stored at 20C in labeled plastic bags. The hormone metabolites were subsequently extracted and assayed using the two commercial kits. Previously it was performed a trial with the DPC kit to check the best extraction method for hormones metabolites. Data were analyzed with the SAS program for Windows V8 and reported as means ± SEM. The Schwarzenberger extraction method was slightly better when compared with the Wasser extraction method (103,334.56 ± 19,010.37ng/g of wet feces and 59,223.61 ± 12,725.36ng/g of wet feces respectively; P=0,0657). The ICN kit detected an increase in glucocorticoid metabolite concentrations in a more reliable manner. Metabolite concentrations (ng/g wet feces) on day 0 and day 1 were 66,956.28 ± 36,786.93 and 92,991.19 ± 28,555.63 for the DPC kit, and 205,483.32 ± 83,811.32 and 814,578.75 ± 292,150.47 for the ICN kit, respectively. The limit of detection for the ICN kit was 7.7 ng/mL for 100% B/Bo (25ng/mL for 88%B/Bo) and for the DPC kit it was 0.2ug/dL for 90.95% B/Bo (1ug/dL for 81.27% B/Bo). In conclusion it was confirmed that the Schwarzenberger extraction method and the ICN kit are superior for extracting and measuring fecal glucocorticoid metabolites in ocelot fecal samples.

Preparation and microbiological analysis of Tuscan sausage with added propolis extract

Abstract The aim of this study was to obtain hydroethanolic extract of propolis by extraction, assisted by focused microwave, and to apply it in Tuscan-style sausage. The extract was used at concentrations of 0.5%, 1.0% and 2.0% (w/v) in the manufacture of the sausage, which was then analyzed in cold storage at 4 °C for 56 days. The following analyses were performed: mesophilic and psychotrophic organisms; coliforms at 35 and 45 °C; positive and negative-coagulase Staphylococcus, sulfite-reducing Clostridium, and Salmonella spp. The results were below the limits established by the Brazilian legislation, with some changes at the end of the study. Consequently, propolis extract prolonged the shelf life of the Tuscan-style sausage for 56 days and it is therefore an ingredient that can be potentially used in the preparation of this product.

Microwave treatment of human milk to prevent transmission of Chagas disease

It is recognized that breast feeding is an alternative means of transmission of Chagas disease. However, thermal treatment of milk can prevent this occurrence. As domestic microwave ovens are becoming commonplace, the efficacy of microwave thermal treatment in inactivating Trypanosoma cruzi trypomastigotes in human milk was tested. Human milk samples infected with T. cruzi trypomastigotes (Y strain) from laboratory-infected mice, were heated to 63 °C in a domestic microwave oven (2 450 MHz, 700 W). Microscopical and serological examinations demonstrated that none of the animals inoculated orally or intraperitoneally with infected milk which had been treated, got the infection, while those inoculated with untreated, infected milk, became infected. It was concluded that the simple treatment prescribed, which can easily be done at home, was effective in inactivating T. cruzi trypomastigotes contained in human milk.

Protocol for DNA extraction of Cryptosporidium spp. oocysts in fecal samples

Molecular characterization of Cryptosporidium spp.oocysts in clinical samples is useful for public health since it allows the study of sources of contamination as well as the transmission in different geographical regions. Although widely used in developed countries, in Brazil it is restricted to academic studies, mostly using commercial kits for the extraction of genomic DNA, or in collaboration with external reference centers, rendering the method expensive and limited. The study proposes the application of the modifications recently introduced in the method improving feasibility with lower cost. This method was efficient for clinical samples preserved at -20 °C for up to six years and the low number of oocysts may be overcomed by repetitions of extraction.

Evaluation of three different DNA extraction methods from blood samples collected in dried filter paper in Plasmodium subpatent infections from the Amazon region in Brazil

Asymptomatic Plasmodium infection is a new challenge for public health in the American region. The polymerase chain reaction (PCR) is the best method for diagnosing subpatent parasitemias. In endemic areas, blood collection is hampered by geographical distances and deficient transport and storage conditions of the samples. Because DNA extraction from blood collected on filter paper is an efficient method for molecular studies in high parasitemic individuals, we investigated whether the technique could be an alternative for Plasmodium diagnosis among asymptomatic and pauciparasitemic subjects. In this report we compared three different methods (Chelex®-saponin, methanol and TRIS-EDTA) of DNA extraction from blood collected on filter paper from asymptomatic Plasmodium-infected individuals. Polymerase chain reaction assays for detection of Plasmodium species showed the best results when the Chelex®-saponin method was used. Even though the sensitivity of detection was approximately 66% and 31% for P. falciparum and P. vivax, respectively, this method did not show the effectiveness in DNA extraction required for molecular diagnosis of Plasmodium. The development of better methods for extracting DNA from blood collected on filter paper is important for the diagnosis of subpatent malarial infections in remote areas and would contribute to establishing the epidemiology of this form of infection.

EVALUATION OF FOUR DIFFERENT DNA EXTRACTION METHODS IN COAGULASE-NEGATIVE STAPHYLOCOCCI CLINICAL ISOLATES

Currently there are several methods to extract bacterial DNA based on different principles. However, the amount and the quality of the DNA obtained by each one of those methods is highly variable and microorganism dependent, as illustrated by coagulase-negative staphylococci (CoNS) which have a thick cell wall that is difficult to lyse. This study was designed to compare the quality and the amount of CoNS DNA, extracted by four different techniques: two in-house protocols and two commercial kits. DNA amount and quality determination was performed through spectrophotometry. The extracted DNA was also analyzed using agarose gel electrophoresis and by PCR. 267 isolates of CoNS were used in this study. The column method and thermal lyses showed better results with regard to DNA quality (mean ratio of A260/280 = 1.95) and average concentration of DNA (), respectively. All four methods tested provided appropriate DNA for PCR amplification, but with different yields. DNA quality is important since it allows the application of a large number of molecular biology techniques, and also it's storage for a longer period of time. In this sense the extraction method based on an extraction column presented the best results for CoNS.