Sistema para realização de medidas de luminescência com excitação por Raios X

In this work is presented a versatile system for X-ray excited optical luminescence (XEOL) measurements. The apparatus was assembled from a sample holder connected to an optical fiber responsibly for the acquisition of the scintillation signal. The spectrum is registered with a CCD coupled in a spectrograph provided with diffraction gratings. The system performance was analyzed by exciting GdAlO3:Eu3+ 3.0 at.% with X-rays from a diffractometer and measuring the emission spectra. The system can be used to obtain precise and reliable spectroscopic properties of samples with various conformations without the loss of the required safety when dealing with ionizing radiations.

Quantificação de antimônio em garrafas de politereftalato de etileno (PET) brasileiras por fluorescência de raios-X e avaliação quimiométrica para verificar a presença de pet reciclado através do teor de ferro

Antimony is a common catalyst in the synthesis of polyethylene terephthalate used for food-grade bottles manufacturing. However, antimony residues in final products are transferred to juices, soft drinks or water. The literature reports mentions of toxicity associated to antimony. In this work, a green, fast and direct method to quantify antimony, sulfur, iron and copper, in PET bottles by X-ray fluorescence spectrometry is presented. 2.4 to 11 mg Sb kg-1 were found in 20 samples analyzed. The coupling of the multielemental technique to chemometric treatment provided also the possibility to classify PET samples between bottle-grade PET/recycled PET blends by Fe content.

Determinação de Mn e Zn em arroz empregando espectrometria de fluorescência de raios x de energia dispersiva

A simple, fast and inexpensive method was developed to determine essential elements in pellets of rice samples using energy dispersive X-ray fluorescence spectrometry (EDXRF). The accuracy and precision were evaluated using Standard Reference Material (rice flour NIST 1568a), and yielding relative standard deviation below 5%. The paired t-test showed good agreement within 95% confidence values. The detection limits (3σ) of Mn and Zn were 5.1 and 2.2 mg kg-1, respectively. The proposed method proved to be effective when used to determine Mn and Zn in commercial samples of rice without go by stage of decomposition.

Combined experimental powder X-ray diffraction and DFT data to obtain the lowest energy molecular conformation of friedelin

Friedelin molecular conformers were obtained by Density Functional Theory (DFT) and by ab initio structure determination from powder X-ray diffraction. Their conformers with the five rings in chair-chair-chair-boat-boat, and with all rings in chair, are energy degenerated in gas-phase according to DFT results. The powder diffraction data reveals that rings A, B and C of friedelin are in chair, and rings D and E in boat-boat, conformation. The high correlation values among powder diffraction data, DFT and reported single-crystal data indicate that the use of conventional X-ray diffractometer can be applied in routine laboratory analysis in the absence of a single-crystal diffractometer.

Análise exploratória rápida e não destrutiva (screening) da presença de elementos químicos tóxicos em material escolar por fluorescência de raios x

Compulsory in Brazil, toy certification aims to prevent possible risks in toy use. The Brazilian National Institute of Metrology (INMETRO) establishes the maximum concentration of toxic elements (TE) that may be present in toys. This study evaluates the presence of TE in different crayons, gouache and modeling clays using X-ray fluorescence. This technique is fast, has low operating cost and minimum sample pretreatment, resulting in a clean procedure without reagent consumption and waste generation. Bromine (in gouache) and Barium (in crayons) were the only potentially TE identified in the samples studied.

Acoplamento de cloreto de 4-nitrofenildiazônio com nucleófilos alifáticos: experimento integrado de síntese orgânica e cristalografia de raios X

This article describes an undergraduate experiment for the synthesis of p-nitrophenyldiazonium chloride and its coupling with acetylacetone and two enaminones, 4-phenylamino-pent-3-en-2-one and 4-amino-pent-3-en-2-one, in an adaptation of a previously reported synthetic protocol. The azo dyes 4-(E)-phenylamino-3-[(E)-2-(4-nitrophenylazo)]-3-penten-2-one and 4-(E)-amino-3-[(E)-2-(4-nitrophenylazo)]-3-penten-2-one were obtained, and the solid state structure of this latter azo compound was characterized by single crystal X-ray diffraction studies. This two-week integrated laboratory approach involves simple synthetic experiments and microwave chemistry in the organic laboratory plus crystallography analysis, suitable for novice students on undergraduate experimental chemistry courses.

Nanoporous materials: pillared clays and regular silicas as an example of synthesis and their porosity characterization by X-ray diffraction

Because of their practical applications, porous materials attract the attention of undergraduate students in a way that can be used to teach techniques and concepts in various chemistry disciplines. Porous materials are studied in various chemistry disciplines, including inorganic, organic, and physical chemistry. In this work, the syntheses of a microporous material and a mesoporous material are presented. The porosity of the synthesized materials is characterized by X-ray diffraction analysis. We show that this technique can be used to determine the pore dimensions of the synthesized materials.

DERIVATIZACIÓN Y CARACTERIZACIÓN ESPECTROSCÓPICA DE UN BIOPOLÍMERO A BASE DE L -LISINA CON ANÁLOGOS DE LA D-BIOTINA: CO -POLI(L-LISINA)-GRAFT -(ε-N-[X-D -BIOTINIL]-L-LISINA)

We report the single-step derivatization reaction of a biopolymer based onL -lysine with D -biotin analogs:Co -poly(L -lysine)-graft-(ε-N -[X-D-biotinyl]-L -lysine) (PLL-X-Biotin). The valeric acid carboxylate of D -biotin is activated to an NHS ester for direct modification of amine groups in proteins and other macromolecules. NHS esters react by nucleophilic attack of an amine in the carbonyl group, releasing the NHS group, and forming a stable amide linkage. NHS-X-Biotin is the simplest biotinylation reagent commercially available. In contrast withD -biotin, it has a longer spacer arm off the valeric acid side chain allowing better binding potential for avidin or streptavidin probes. Derivatization of poly(L -lysine) (PLL) with NHS-X-Biotin led to a copolymer PLL-X-Biotin. UV-Visible, IR-FT and 1H NMR characteristics derived from synthesis are briefly discussed.

Identificação de xanthomonas axonopodis pv. phaseoli e x. axonopodis pv. phaseoli var. fuscans através da técnica de pcr

Este trabalho teve por objetivo verificar a viabilidade de utilização da técnica de PCR, usando primers considerados específicos, para identificação de Xanthomonas axonopodis pv. phaseoli (Xap) e x. axonopodis pv. phaseoli var. fuscans (Xapf), visando criar bases para sua utilização em diagnose rotineira e em programas de certificação de sementes. Foram incluídos no estudo 42 isolados da bactéria provenientes de locais distintos, além de outros gêneros, espécies e patovares, para ser verificada a especificidade dos primers. Os resultados obtidos permitem concluir que os primers utilizados são adequados para identificação de Xap e Xapf, embora dois isolados patogênicos não tenham sido amplificados. Foi observada também a amplificação de uma banda fraca para X. axonopodis pv. vitians, com o mesmo número de pares de bases, o que sugere existir homologia entre estes patovares, na região amplificada.

Effects of single and double infections with Potato virus X and Tobacco mosaic virus on disease development, plant growth, and virus accumulation in tomato

The tomato cv. Fukuju nº. 2 was used for studying the effect of single and double infections with Potato virus X (PVX) and Tobacco mosaic virus (TMV). Mixed infection resulted in a synergistic increase of disease severity, where more growth reduction was seen with simultaneous inoculations than with sequential inoculations at four-day intervals. At five and 12 days post-inoculation, the increased severity of the disease coincided with enhancement of virus accumulation in the rapidly expanding upper leaves. The PVX concentration in leaves nº 5 to 7 of doubly infected plants was three to six fold that of singly infected ones, as determined by DAS-ELISA. Mixed infection with the L strain led to higher enhancement of PVX than with the TMV-L11A strain. The concentration of TMV-L was lower in double infection and significantly higher than TMV-L11A in both singly and doubly infected plants. Analyses of the PVX ORF2 by Western blot and Northern hybridization revealed the pattern of accumulation of the 25 kDa protein and the RNAs, respectively, following those of the virion and coat protein. The strain TMV-L11A overcame the resistance gene in cv. GCR 237 (Tm-1). In the upper leaf nº. 8, the concentration of PVX was three times higher in plants with mixed infection than with L11A. The concentrations of the L and OM (TMV strains) in both singly and doubly infected plants were at very low levels, and the synergistic effect on PVX concentration and disease severity was not observed.

Thermal decomposition and stability in a series of heterobimetallic carbonyl compounds of the type [Fe(CO)4(HgX)2] (X=Cl, Br, I)

Heterobimetallic carbonyl compounds of the type [Fe(CO)4(HgX)2] (X= Cl, Br, I), which have metal-metal bonds, have been prepared in order to study their thermal stabilities as a function of the halogen coordinated to mercury atoms. The characterization of the above complexes was carried out by elemental analysis, IR and NMR spectroscopies. Their thermal behaviour has been investigated and the final product was identified by IR spectroscopy and by X-ray powder diffractogram.

Clivagem dos ciclopaladados diméricos [Pd(dmba)(m-X)]2 (dmba = N,N-dimetilbenzilamina; X = Cl, N3, NCO) por tiouréia

Ciclopaladados diméricos do tipo [Pd(dmba)(m-X)]2 (dmba = N,N-dimetilbenzilamina; X = Cl, N3, NCO) reagem com tiouréia (tu), à temperatura ambiente, resultando espécies mononucleares do tipo [Pd(dmba)(X)(tu)]. Todos os compostos foram caracterizados por análise elementar, espectroscopias no IV e de RMN de ¹H e com base nessas técnicas as estruturas, desses compostos, foram propostas. Os espectros de absorção no infravermelho mostraram que a coordenação da tiouréia, ao paládio, ocorre através do átomo de enxofre. O anel ciclometalado foi confirmado através da espectroscopia de RMN de ¹H.