Determination of cadmium in river water samples by flame AAS after on-line preconcentration in mini-column packed with 2-aminothiazole-modified silica gel.

A rapid and sensitive method was developed to determine trace levels of Cd2+ ions in an aqueous medium by flame atomic absorption spectrometry, using on-line preconcentration in a mini-column packed with 100 mg of 2-aminothiazol modified silica gel (SiAT). The Cd2+ ions were sorbed at pH 5.0. The preconcentrated Cd2+ ions were directly eluted from the column to the spectrometer's nebulizer-burner system using 100 microL of 2 mol L(-1) hydrochloric acid. A retention efficiency of over 95% was achieved. The enrichment factor (calculated as the ratio of slopes of the calibration graphs) obtained with preconcentrations in a mini-column packed with SiAT (A = -1.3 x 10(-3) + 1.8 x 10(-3)[Cd2+]) and without preconcentrations (A = 4 x 10(-5) + 3.5 x 10(-5)[Cd2+]), was 51 and the detection limit calculated was 0.38 microg L(-1). The preconcentration procedure was applied to determine trace levels of Cd in river water samples. The optimum preconcentration conditions are discussed herein.     

Salbutamol extraction from urine and its stability in different solutions: identification of methylation products and validation of a quantitative analytical method

Salbutamol is commonly used in asthma treatment, being considered a short‐effect bronchodilator. This drug poses special interest in certain fields of chemical analysis, such as food, clinical and doping analyses, in which it needs to be analyzed with quantitative precision and accuracy. Salbutamol, however, is known to degrade under certain conditions and this is critical if quantitative results must be generated. The present work aimed to investigate salbutamol extraction from urine samples, to determine whether salbutamol is unstable in other solvents as well as in urine samples, to elucidate the structures of the possible degradation products and to validate an analytical method using the extraction procedure evaluated. Stability investigations were performed in urine at different pH values, in methanol and acetone at different temperatures. Semi‐preparative liquid chromatography was performed for the isolation of degradation products, and gas chromatography coupled to mass spectrometry as well as nuclear magnetic resonance were used for identification. Three unreported methylation products were detected in methanolic solutions and had their structures elucidated. Urine samples showed a reduction in salbutamol concentration of up to 25.8% after 5 weeks. These results show that special care must be taken regarding salbutamol quantitative analyses, since degradation either in standard solutions or in urine could lead to incorrect values. Copyright © 2013 John Wiley & Sons, Ltd.     

Strong two-photon absorption at telecommunications wavelengths in nickel bis(dithiolene) complexes

The two-photon absorption spectrum of a nickel bis(dithiolene) complex with extended conjugation and pi-donor substitution is measured by using Z-scan and pump-probe techniques with femtosecond pulses over the spectral range from 1.20 to 1.58 microm, which includes much of the telecommunications range. The peak two-photon cross section of over 5000 GM (1 GM = 10(-50) cm4 s photon(-1) molecule(-1)) occurs at approximately 1.24 microm, with significant two-photon absorption (>440 GM) throughout the spectral range examined.     

Selenium determination in tissue samples of Nile tilapia using ultrasound-assisted extraction

This paper proposes a method to determine selenium in samples of fish muscle and liver tissue using ultrasound assisted extraction process, and analysed by graphite furnace atomic absorption spectrometry (GFAAS). The selenium content was extracted by 0.10 M HCl at the optimal extraction conditions which were established as follows: sample mass of 100 mg; granulometry of the sample <60 μm; sonication time of five 40 s cycles; and sonication power of 136 W. The selenium determinations were performed by GFAAS, at a drying temperature of 120°C/250°C, pyrolysis temperature of 1300°C, atomization temperature of 2300°C, and cleaning temperature of 2800°C. Palladium nitrate was used as a chemical modifier coinjected with the samples, and tungsten as a permanent modifier. The concentration of selenium determined in the pool of fish muscle and liver tissue were 280.4±4.2 e 592.3±6.7 μg kg⁻¹, respectively. The accuracy and precision of the proposed extraction method were evaluated using certified standard Bovine Muscle — NIST 8414. The results obtained by the ultrasonic extraction method were equivalent to those obtained by the method of acid mineralization of samples in a microwave oven     

Structure and linear spectroscopic properties of near IR polymethine dyes

We performed a detailed experimental investigation and quantum-chemical analysis of a new series of near IR polymethine dyes with 5-butyl-7,8-dihydrobenzo[cd]furo[2,3-f]indolium terminal groups. We also synthesized and studied two neutral dyes, squaraine and tetraone, with the same terminal groups and performed a comparison of the spectroscopic properties of this set of “near IR” dyes (polymethine, squaraine, and tetraone) with an analogous set of “visible” dyes with simpler benzo[e]indolium terminal groups. From these measurements, we find that the dyes with dihydrobenzo[cd]furo[2,3-f]indolium terminal groups are characterized by a remarkably large shift ≈300 nm (≈200 nm for tetraone) of their absorption bands towards the red region. We discuss the difference in electronic structure for these molecules and show that the “near IR” dyes are characterized by an additional weak fluorescence band from the higher lying excited states connected with the terminal groups. Absorption spectra for the longest polymethines are solvent-dependent and are characterized by a broadening of the main band in polar solvents, which is explained by ground state symmetry breaking and reduced charge delocalization within the polymethine chromophore. The results of these experiments combined with the agreement of quantum chemical calculations moves us closer to a predictive capability for structure-property relations in cyanine-like molecules.     

Production and rheological characterization of biopolymer of Sphingomonas capsulata ATCC 14666 using conventional and industrial media

This work was aimed at the production and rheological characterization of biopolymer by Sphingomonas capsulata ATCC 14666, using conventional and industrial media. The productivity reached the maximum of 0.038 g/L·h, at 208 rpm and 4% (w/v) of sucrose. For this condition, different concentrations of industrial medium were tested (2.66, 4, 6, and 8%). The best productivity was obtained using pretreated molasses 8% (w/v) (0.296 g/L·h), residue of textured soybean protein 6% (wt/v) (0.244 g/L·h) and crude molasses 8% (w/v) (0.192 g/L·h), respectively. Apparent viscosity presented similar results when compared with those in the literature for other biopolymers.     

Determination of Cu,Ni, and Zn in fuel ethanol by FAAS after enrichment in column packed with 2-aminothiazole-modified silica gel

This work describes the synthesis and characterization of 2-aminothiazole-modified silica gel (SiAT), as well as its application for preconcentration (in batch and column technique) of Cu(II), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities of SiAT determined for each metal ion were (mmol g(-1)): Cu(II)=1.20, Ni(II)=1.10 and Zn(II)=0.90. In addition, results obtained in flow experiments, showed a recovery of ca. 100% of the metal ions adsorbed in a column packed with 500 mg of SiAT. The eluent was 2.0 mol L(-1) HCl. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in fuel ethanol using flame AAS for their quantification.     

Coexistence of superfluid and metallic-like state in two-component fermionic systems

We study the possibility of coexistence in a two component fermionic system of a superfluid state with a metallic-like state with gapless excitations at a Fermi surface. We consider a two-component system with mixing (hybridization) between them and attractive interactions between only one type of quasi-particles. Besides a conventional BCS regime, we find for sufficiently strong interactions a superfluid state of Bose condensed pairs at zero temperature. We investigate whether these pairs can coexist with a metallic-like state characterized by gapless electronic excitations. The zero temperature phase diagram as a function of the strength of the attractive interaction and the mixing is obtained. For simplicity and to clarify the nature of the quantum phase diagram we consider the case of s-wave pairing.