Comparison of single extraction procedures,using either conventional shaking or microwave heating,and the Tessier sequential extraction method for the fractionation of heavy metals from environmental samples

The conventional four-step sequential extraction method and the EDTA and acetic acid single extraction procedures were applied to sewage sludge and sediment samples. The results obtained with these samples for Cu, Cr, Ni, Pb and Zn using the Tessier method were compared with those supplied by the two single extraction procedures employed. In addition, the Tessier method was also applied to a reference material, CRM 483, and these results were also compared with the certified EDTA and acetic acid values for this sample. As a result, good agreement was found between the metal contents released in the first three fractions of the Tessier method and those leached by the simpler single extraction procedures for the most of the elements studied. Subsequently, the conventional EDTA and acetic acid extraction methods were accelerated by means of microwave energy, in order to reduce the operating time. The extraction efficiency of the first three fractions of the Tessier method was compared with that obtained using the optimised microwave single extraction procedures and only in sewage sludge and CRM 483 samples were satisfactory results found for all the elements studied, except Cr and Pb. This means that the microwave single extraction procedures optimised in this work could be employed as screening methods to evaluate rapidly the easiest mobilizable heavy metals in these samples, although more samples should be analysed to determine their general applicability. The application of the accelerated single extraction procedures to a reference material, CRM 483, provided satisfactory results for all the elements studied, except for Cr in both methods and for Pb in the acetic acid extracts.     

Identification of anhydroecgonine methyl ester N-oxide,a new metabolite of anhydroecgonine methyl ester,using electrospray mass spectrometry

Cocaine is transformed into hepatotoxic metabolites through oxidative pathways. For anhydroecgonine methyl ester (AEME), the main constituent in crack smoke, the oxidative metabolism has not been studied. Therefore, incubation of AEME with rat liver microsomes was performed and a metabolite of AEME, anhydroecgonine methyl ester N-oxide (AEMENO), was identified. The chemical structure of this new metabolite was confirmed by synthesis and by comparative interpretation of electrospray multiple-stage mass spectra, which were obtained in the positive ion mode. This metabolite was also detected in whole blood, serum and urine samples from crack users. The application of liquid chromatography/electrospray mass spectrometry or nanoelectrospray mass spectrometry was necessary because AEMENO is susceptible to thermal degradation during gas chromatographic/mass spectrometric analysis. This study demonstrated that AEMENO is produced by rat hepatic microsomal metabolism in vitro and is present in body fluids from crack users.     

Beer Digestions for Metal Determination by Atomic Spectrometry and Residual Organic Matter

Many standard and official sample digestion procedures for trace metal determination are carried out in open vessels on hot plates. A new procedure for the determination of trace metals by flame atomic absorption spectrometry or inductively coupled plasmaatomic emission spectrometry in beer samples was developed to be performed in closed reactors assisted by microwaves. The results are compared with the ones obtained by other procedures by means of the analysis of the variance. The differences between the procedures are attributed to residual organic matter. Voltammetry, absorption molecular spectrophotometry and high pressure liquid chromatography with a photodiode array detector are used to study the nature of these residues. Nitrobenzoic acids, phenolic acids and other organic compounds are often present after digestion. The results obtained are related to the precision in metal determination by atomic spectrometry. The need for elaboration of certified reference materials for trace metals in beer is suggested.     

Elucidation of the pore structure of SBA-2 using Monte Carlo simulation to interpret experimental data for the adsorption of light hydrocarbons

We have measured the adsorption of methane and ethane to high pressure on SBA-2, a structured mesoporous silica composed of spheres connected by narrow channels. The experimental data were analyzed by carrying out Monte Carlo simulations of adsorption in pore structure models of different complexity and then adjusting the parameters of the models to match the Monte Carlo results to the experimental data. We found that a model based on single-sized spherical cavities was inadequate and that it is necessary to explicitly account for the interconnecting channels. Further, we found that despite the basic regularity of the SBA-2 structure, it is necessary to allow for a distribution of the sizes of both the cavities and the channels. These size distributions were obtained by fitting the parameters of the model to the experimental adsorption data, revealing detailed structural information not previously known for this material. The channels were found to be 5-15 A in diameter, while the cavities were 40-50 A in diameter. There is some evidence that the distribution of channel sizes leads to a percolation effect whereby the pore structure is not equally accessible to all adsorptives.     

Synthesis of α-Metoylene-γ-Lactones in Furanosidic Systems

Abstract

Synthesis of stereoisomeric α-methylene-γ-lactones in furanose-and furanuronoamide derivatives was easily accomplished by Reformatsky Reaction with ethyl bromcmethylacrylic ester and zinc. Pyridinium chlorochromate/3Å molecular sieve powder showed to be an excellent reagent for the oxidation of secondary hydroxyl groups of a furanose system and of α-hydroxy amides.     

Evaluation of micellar liquid chromatography and capillary zone electrophoresis for dope control in sport

Micellar liquid chromatography (MLC) and capillary zone electrophoresis (CZE) have been evaluated for the analysis of twelve banned drugs in sport including diuretics and -blockers. In MLC, a sodium dodecylsulphate aqueous solution has been used as mobile phase using an octadecylsilica column. In CZE, a pH 8 buffer solution and a silica capillary have been employed. Parameters of retention and efficiency have been compared. Limits of detection with UV detection at 254 nm and relative standard deviations for atenolol, furosemide, nadolol, spironolactone and triamterene were established and compared in both techniques. Examples of direct urine injection into the separation systems are presented. Drugs overlapping in MLC are well resolved in CZE, while the opposite is true for a limited number of drugs. Some interferences from urine may arise in CZE. The selectivity of analysis would be greatly enhanced by using both techniques, which require only filtration as pre-treatment.     

Effect of flame-sprayed Al–12Si coatings on the failure behaviour of pressurized fibre-reinforced composite tubes

Internal pressurization testing at room temperature was performed to evaluate the effect of flame-spraying aluminum-12silicon on the leakage behavior of fibre-reinforced composite tubes fabricated by filament winding, and covered with garnet sand. A group of specimens were completely coated with flame-sprayed metal particles and another set remained uncoated. t-tests were conducted at a significance level of α = 0.05 to analyze the effect of the coating on the leakage behavior of the specimens. Ultraviolet imaging was used to illustrate a characteristic leakage pattern of the composite tubes. Coated specimens exhibited slightly higher mean leakage and burst pressures than the uncoated specimens. The t-test results provided strong statistical evidence that the flame spraying process employed did not damage the filament wound tubes covered with garnet sand.