Comparative study of conventional and multivariate methods for aluminum determination in soft drinks by graphite furnace atomic absorption spectrometry

In the present study, conventional and multivariate methods were used to optimize conditions for direct determination of aluminum in soft drinks by electrothermal atomic absorption spectrometry. For the conventional method, the optimized experimental parameters were: pyrolysis and atomization temperatures and chemical modifier. A multivariate study was performed using factorial design and the optimized parameters were the same employed in the univariate method including pyrolysis time. For the conventional method, the optimal conditions obtained were: pyrolysis temperature of 1600 °C, atomization temperature of 2700 °C, and Zr as permanent modifier. For the factorial design in the multivariate optimization, the Pareto´s chart showed that the atomization temperature, the modifier, and the pyrolysis temperature presented a significant effect on the integrated absorbance and the interaction between pyrolysis temperature and pyrolysis time also had a significant effect on the signal. Better results were obtained using Zr as modifier. The surface response indicates that the lowest pyrolysis (1100 °C) and atomization temperatures (2350 °C) provide higher absorbance for aluminum in soft drinks. Characteristic mass of 23.4 and 19.4 pg and LOD of 17.9 and 11.3 μg L^− 1 was obtained to conventional and multivariate methods, respectively. The calibration was accomplished with standard addition in a range of 60–200 μg L^− 1 for conventional method and of 38–200 μg L^− 1for multivariate method with R higher than 0.99 for both conditions. Recoveries in both studies were nearly 100% with adequate precision for GFAAS analysis. For the Al concentrations level found in soft drinks, both experimental conditions are adequate as good results were obtained in recovery studies. The Al concentrations in different soft drinks range from 147.9 to 599.5 μg L⁻¹. Higher concentrations were found in soft drinks sold in Al cans than in PET bottles, indicating that contamination can occur.     

Order-disorder phase transition in p-terphenyl and p-terphenyl: tetracene doped crystals as studied by Raman spectroscopy

Phase transition in crystalline pure p-terphenyl and p-terphenyl: tetracene doped crystals was studied with Raman spectroscopy, for temperatures from 295 to 10 K. In particular, the torsional Raman vibrational mode with a “hard-core frequency” of 230.8 cm⁻¹ was investigated in its frequency and bandwidth dependence upon temperature. The results were analyzed based on an order-disorder model allowing the determination of the activation energies and orientational correlation times of the molecular diffusive process in the monoclinic (above 193 K) and triclinic (below 193 K) phases of the crystals. The activation energy is observed to decrease from the monoclinic to the triclinic phase, whereas the orientational correlation times increase, both in the undoped and the doped crystals. The doping of p-terphenyl with tetracene appears to affect the activation energy and the orientational correlation times in a different way in each phase.     

Atmospheric Pressure Plasma Pretreatment of Sugarcane Bagasse: The Influence of Moisture in the Ozonation Process

Sugarcane bagasse samples were pretreated with ozone via atmospheric O₂ pressure plasma. A delignification efficiency of approximately 80 % was observed within 6 h of treatment. Some hemicelluloses were removed, and the cellulose was not affected by ozonolysis. The quantity of moisture in the bagasse had a large influence on delignification and saccharification after ozonation pretreatment of the bagasse, where 50 % moisture content was found to be best for delignification (65 % of the cellulose was converted into glucose). Optical absorption spectroscopy was applied to determine ozone concentrations in real time. The ozone consumption as a function of the delignification process revealed two main reaction phases, as the ozone molecules cleave the strong carbon–carbon bonds of aromatic rings more slowly than the weak carbon–carbon bonds of aliphatic chains.     

Palladium supported on structured and nonstructured carbon: a consideration of Pd particle size and the nature of reactive hydrogen

This study sets out a comprehensive characterization of bulk Pd and Pd (ca. 8% w/w) supported on activated carbon (AC), graphite and graphitic nanofibers (GNF). Catalyst activation has been examined by temperature programmed reduction (TPR) analysis and the activated catalysts analyzed in terms of BET area, TEM, H2 chemisorption/TPD, and XRD measurements. While H2 chemisorption and TEM delivered the same sequence of increasing (surface area weighted) average Pd particle sizes, a significant difference (by up to a factor of 3) in the values obtained from both techniques has been recorded and is attributed to an unwarranted (but widely adopted) assumption of an exclusive H2/Pd adsorption stoichiometry=1/2. It is demonstrated that TEM analysis provides a valid mean particle size once it is established that the associated standard deviation is small and insensitive to additional particle counting. XRD line broadening yielded an essentially equivalent Pd size (20-25 nm) for each supported catalyst. The nature of the hydrogen associated with the supported catalysts has been probed and is shown to comprise of chemisorbed (on Pd), spillover (on the carbon support), and hydride (associated with Pd) species. Physical mixtures of bulk Pd + support (AC, graphite, and GNF) were also considered in order to assess hydrogen spillover by H2 TPD analysis. Generation of spillover hydrogen at room temperature is established where temperatures in excess of 740 K are required for effective desorption from the supported Pd catalysts, i.e., 280 K higher than that required for the desorption of chemisorbed hydrogen. Pd hydride formation (at room temperature) is shown to be reversible with decomposition occurring at ca. 380 K. Taking the hydrodechlorination of chlorobenzene as a test reaction, the capability of Pd hydride to promote a hydrogen scission of C-Cl in the absence of an external supply of H2 is demonstrated with a consequent consumption of the hydride. This catalytic response was entirely recoverable once the Pd hydride was replenished during a subsequent reactivation step.     

On‐Site Determination of Carbendazim,Cathecol and Hydroquinone in Tap Water Using a Homemade Batch Injection Analysis Cell for Screen Printed Electrodes

In this work, we present a simple homemade batch‐injection analysis cell for screen‐printed electrodes (BIA‐SPE). The potential of the proposed system for on‐site analysis was demonstrated by the determination of carbendazim, catechol, and hydroquinone in tap water. The system provided reduced injection volume (30 µL), high analytical frequency (≈200 h^?1) and low detection limits (nanomolar level). Moreover, the BIA‐SPE cell presented better stability (RSD≈0.4 %) than a conventional flow injection cell for SPE (RSD≈5.0 %) in organic media. The proposed homemade BIA‐SPE cell is very simple, inexpensive and can be easily constructed in any laboratory.     

A novel antinociceptive sulphated polysaccharide of the brown marine alga Spatoglossum schroederi

Sulfated polysaccharides (SP) of brown algae (Phaeophyta) are composed mainly of alpha- L-fucose, being classified as fucans, with recognized role in inflammation but not in nociception, which was already described for SP obtained from red algae. Here the SP of the brown marine alga S. schroederi (named Ss-SP) was isolated and assayed for the antinociceptive effect. Ss-SP was isolated by DEAE-cellulose, analyzed by agarose gel electrophoresis and evaluated in nociception models (Formalin, Hot plate, Von Frey) using Swiss mice (20-25g). Anion exchange chromatography provided four major fractions being F1 (Ss-SP) that of highest metachromatic activity and sugar content. Ss-SP inhibited both phases of the formalin test. In the first phase the paw licking (55.2 +/- 8.07s) was reduced by 45% (30.5 +/- 6.51s) and 40% (32.85 +/- 8.66s) at 0.1 and 1 mg/kg, respectively. In the second phase, Ss-SP was also inhibitory about 39%, but only at 1 mg/kg (83.0 +/- 15.70s) compared to formalin (136.8 +/- 10.27s). This inhibitory effect suggests a mixed mechanism similar to morphine, which was not confirmed in the hot plate test, a model of pain associated with central neurotransmission. However, Ss-SP reduced the animal reaction in response to stimulation withVon Frey filament at the 2nd and 3rd h (20.8 +/- 6.86% versus carrageenan: 47.9 +/- 5.83%; 33.3 +/- 7.71% versus carrageenan: 62.5 +/- 9.83%). Accordingly, the paw edema induced by carrageenan (0.08 +/- 0.01g) was potently reduced in 45.35% by Ss-SP pre-treatment (0.02 +/- 0.003g), corroborating the anti-inflammatory activity demonstrated for brown seaweed polysaccharides. In conclusion our data revealed for the first time the antinociceptive effect of Ss-SP which could be used as a new source of analgesic substances.     

Cryptococcus gattii: in vitro susceptibility to photodynamic inactivation

Cryptococus gattii is an emergent primary human pathogen that causes meningismus, papilledema, high intracranial pressure and focal involvement of the central nervous system in immunocompetent hosts. Prolonged antifungal therapy is the conventional treatment, but it is highly toxic, selects for resistant strains, contributes to therapy failure and has a poor prognosis. Photodynamic inactivation (PDI) offers a promising possibility for the alternative treatment of cryptococcosis. The aim of this study was to test the effectiveness of toluidine blue O (TBO) and light-emitting diode (LED) against C. gattii strains with distinct susceptibility profile to antifungal drugs (amphotericin B: 0.015-1.0 μg mL(-1); itraconazole: 0.015-2 μg mL(-1); fluconazole: 4-64 μg mL(-1)). Using 25 μM (6.76 μg mL(-1)) TBO and LED energy density of 54 J cm(-2) these fungal isolates presented variable susceptibility to PDI. The production of reactive oxygen species (ROS)/peroxynitrite was determined, and the catalase and peroxidase activities were measured. After PDI, high amounts of ROS/peroxynitrite are produced and higher catalase and peroxidase activities could be correlated with a lower susceptibility of C. gattii isolates to PDI. These results indicate that PDI could be an alternative to C. gattii growth inhibition, even of isolates less susceptible to classical antifungal drugs, also pointing to mechanisms related to their variable susceptibility behavior.