Dispersive liquid-liquid microextraction based on solidification of floating organic drop for simultaneous separation/preconcentration of nickel, cobalt and copper prior to determination by electrothermal atomic absorption spectrometry

A dispersive liquid-liquid microextraction based on solidification of floating organic drop for simultaneous extraction of trace amounts of nickel, cobalt and copper followed by their determination with electrothermal atomic absorption spectrometry was developed. 300 µL of acetone and 1-undecanol was injected into an aqueous sample containing diethyldithiocarbamate complexes of metal ions. For a sample volume of 10 mL, enrichment factors of 277, 270 and 300 and detection limits of 1.2, 1.1 and 1 ng L-1 for nickel, cobalt and copper were obtained, respectively. The method was applied to the extraction and determination of these metals in different water samples.

A NOVEL METHOD FOR THE DETERMINATION OF TRACE THORIUM BY DISPERSIVE LIQUID-LIQUID MICROEXTRACTION BASED ON SOLIDIFICATION OF FLOATING ORGANIC DROP

In this study, dispersive liquid-liquid microextraction based on the solidification of floating organic droplets was used for the preconcentration and determination of thorium in the water samples. In this method, acetone and 1-undecanol were used as disperser and extraction solvents, respectively, and the ligand 1-(2-thenoyl)-3,3,3-trifluoracetone reagent (TTA) and Aliquat 336 was used as a chelating agent and an ion-paring reagent, for the extraction of thorium, respectively. Inductively coupled plasma-optical emission spectrometry was applied for the quantitation of the analyte after preconcentration. The effect of various factors, such as the extraction and disperser solvent, sample pH, concentration of TTA and concentration of aliquat336 were investigated. Under the optimum conditions, the calibration graph was linear within the thorium content range of 1.0-250 µg L-1 with a detection limit of 0.2 µg L-1. The method was also successfully applied for the determination of thorium in the different water samples.

Anatomic study of the dorsal arterial system of the hand

Historically, the dorsal arterial system of the hand received less attention than the palmar system. The studies concerning dorsal arterial anatomy present some controversies regarding the origin and presence of the dorsal metacarpal artery branches. Knowledge of the anatomy of dorsal metacarpal arteries is especially applied in the surgical planning for flaps taken from the dorsum of the hand. The purpose of this study is to analyze the arterial anatomy of the dorsum of the hand, compare our observations with those of previous studies from the literature, and therefore to define parameters for surgical planning for flaps supplied by the dorsal metacarpal arteries. METHOD: Twenty-six dissections were performed at the dorsum of the right hand of 26 cadavers by making a distal-based U-shaped incision. After catheterization of the radial artery at the wrist level, a plastic dye solution with low viscosity and quick solidification was injected to allow adequate exposure of even small vessels. The radial artery and its branches, the dorsal arterial arch, the dorsal metacarpal arteries, the distal and proximal communicating branches of the palmar system, and the distal cutaneous branches were carefully dissected and identified. RESULTS: The distal cutaneous branches originating from the dorsal metacarpal arteries were observed in all cases; these were located an average of 1.2 cm proximal from the metacarpophalangeal joint. The first dorsal metacarpal artery presented in 3 different patterns regarding its course: fascial, subfascial, and mixed. The branching pattern of the radial artery at the first intermetacarpal space was its division into 3 branches. We observed the presence of the dorsal arterial arch arising from the radial artery in 100% of the cases. The distance between the dorsal arterial arch and the branching point of the radial artery was an average of 2 cm. The first and second dorsal metacarpal arteries were visualized in all cases. The third and fourth dorsal metacarpal arteries were visualized in 96.2% and 92.3% of cases, respectively. There was proximal and distal communication between the dorsal arterial arch and the palmar system through the communicating branches contributing to the dorsal metacarpal artery formation. CONCLUSION: At the dorsum of the hand there is a rich arterial net that anastomoses with the palmar arterial system. This anatomical characteristic allows the utilization of the dorsal aspect of the hand as potential donor site for cutaneous flaps.

Avaliação do uso de poli(tereftalato de etileno) (PET) como matriz de imobilização de cinzas de incineradores

Industrial hazardous wastes must receive appropriate treatment to ensure a safe disposal to humans and environment. One of the techniques adopted for this purpose is the stabilization/solidification in polymer matrices. This paper evaluated the use of recycled polyethylene terephthalate as an incorporation matrix of incinerator ash. The polymer and the ash were submitted to an extrusion process in different percentages. The final product was evaluated through thermal and leaching tests and the leachate extracts constituents were determinated by atomic absorption spectrophotometry. The results showed a reduction in the release of substances up to 99% by mass for the conditions used.

Chocolate rheology

Rheology is the science that studies the deformation and flow of solids and fluids under the influence of mechanical forces. The rheological measures of a product in the stage of manufacture can be useful in quality control. The microstructure of a product can also be correlated with its rheological behavior allowing for the development of new materials. Rheometry permits attainment of rheological equations applied in process engineering, particularly unit operations that involve heat and mass transfer. Consumer demands make it possible to obtain a product that complies with these requirements. Chocolate industries work with products in a liquid phase in conching, tempering, and also during pumping operations. A good design of each type of equipment is essential for optimum processing. In the design of every process, it is necessary to know the physical characteristics of the product. The rheological behavior of chocolate can help to know the characteristics of application of the product and its consumers. Foods are generally in a metastable state. Their texture depends on the structural changes that occur during processing. Molten chocolate is a suspension with properties that are strongly affected by particle characteristics including not only the dispersed particles but also the fat crystals formed during chocolate cooling and solidification. Chocolate rheology is extensively studied, and it is known that chocolate texture and stability is strongly affected by the presence of specific crystals