Silvia M. Sella

Alkaline solubilization of biological materials for trace element analysis by electrothermal atomic absorption spectrometry

An alternative method to acid digestion is presented for the preparation of marine biological tissues and botanical samples for trace metal determination by ETAAS. Samples were solubilized using a methanolic solution of tetramethylammonium hydroxide (TMAH), either overnight at room temperature or by the application of heat and/or ultrasonic agitiation. Following dilution with water, aliquots were sampled into a graphite furnace using a conventional autosampler. External calibration was used for all analyte determinations. Limits of detection, characteristic mass and precision are reported for copper, cadmium, nickel, lead, manganese and chromium. Measured concentrations are in satisfactory agreement with certified values for the biological reference materials DORM-2, DOLT-2, TORT-2 and BCR 060. Samples prepared with TMAH can be stored for up to 3 years at room temperature without any change in analyte concentrations.

Aluminium and Other Metals May Pose a Risk to Children with Autism Spectrum Disorder: Biochemical and Behavioural Impairments

Recent studies have shown that some toxic metals have been associated with neurological diseases. The binding and transport of these metals in the blood may occur by species of High Molecular Mass (HMM) and Low Molecular Weight Species (LMM) of proteins. These main species are known to be responsible for aluminum transporting is the case of transferrin and citrate. It seems that autistic children may have a genetic predisposition to accumulate large amounts of metals as it is has been proposed. This study seeks to understand the toxic mechanism of selected metals in autistic children and its correlation with the psycho-metabolic implications of the syndrome. Preliminary results have indicated that some metals such as chromium, arsenic and particularly aluminum were elevated in the blood of an autistic child, as compared to reference values of a normal child. A case-control study is under investigation. Furthermore, the consequences of the disease, as such the difficulties in socialization and language skill disabilities may also be related to the burden of toxic metals in general, particularly aluminum.

Distribuição espacial de ferro, cobre e chumbo em sedimentos de manguezal em um gradiente de degradação na Baía de Guanabara (Estado do Rio de Janeiro)

Iron, copper and lead distribution was evaluated in sediment cores from a disturbed mangrove area in Guanabara Bay: a core from a seaward site where mangrove vegetation was removed ~20 yr before sampling (MD); a core from an intermediate site with dead vegetation, apparently due to insect attack (MP), and a core from a landward site with living vegetation (MV). Metal concentrations showed increasing values seaward while organic matter content showed an inverse trend, displaying a negative correlation with metals. This unusual correlation indicates opposite sources, since metals come from the bay and the main OM origin is probably degraded mangrove vegetation. Plant cover loss seems to be a critical factor affecting metal accumulation, particularly due to changes in OM input.

Caracterização do material particulado fino e grosso e composição da fração inorgânica solúvel em água em São José dos Campos (SP)

Air samples of fine (PM2,5) and coarse (PM2,5-10) particulate matter were collected in Sao Jose dos Campos from February 2004 to February 2005. Average PM10 mass concentrations was 31.2 ± 14.0 μg m-3, half of which belonging to the PM2.5 fraction. Ammonium and SO42- were predominantly found in the fine fraction. Average (NH4)2SO4 concentration was estimated to be about 2.9 μg m-3. Chloride, Na+ and NO3- were mostly associated with PM2,5-10. Chloride deficits with respect to sea-salt Cl/Na ratio were found in both size fractions.

Efficient removal of mercury from aqueous solutions and industrial effluent.

The objective of this study was to examine the ability of a solid waste produced during beneficiation of ornamental rocks to remove mercury (Hg) from an industrial effluent and aqueous solutions under various conditions. Batch studies have been carried out by observing the effects of pH, concentration of the adsorbate, contact time, and so on. Various sorption isotherm models such as Langmuir, Freundlich, and Tóth have been applied for the adsorbent. Film and intraparticle diffusion were both found to be rate-limiting steps. Adsorption was properly described by the Freundlich model (capacity constant of 0.3090 (mg g−1)(mg L−1)−1/n and adsorption intensity indicator of 2.2939), which indicated a favorable sorption and encouraged subsequent studies for treatment of Hg-containing industrial effluent. Industrial effluent treatment efficiency reached Hg removals greater than 90% by using ornamental rock solid waste (ORSW). Besides, desorption studies indicated that the maximum recovery of mercury was 100 ± 2% for 1 mol L−1 HNO3 and 74 ± 8% for 0.1 mol L−1 HNO3. The ORSW could be reused thrice without significant difference on the Hg removal rate from industrial effluent. These findings place ORSW as a promising efficient and low-cost adsorbent for the removal of Hg from aqueous solutions and industrial effluent.

Vanadium-binding protein in marine plankton from tropical south atlantic ocean

We investigated the role of plankton in the vanadium (V) cycle at Cabo Frio, Rio de Janeiro state, Brazil, a region with high V concentration in the atmospheric particles due to marine aerosol. The concentrations of V in plankton vary from 0.08 to 20.9 µg g-1 (zooplankton), 0.1 to 28.4 µg g-1 (phytoplankton > 64 µm) and 20 µm). The V speciation in biomolecules was performed by the use of two strategies: (i) coupling of size exclusion chromatography (SEC) for the fractionation of species with inductively coupled plasma mass spectrometry (ICP-MS) and (ii) with size exclusion anionic exchange chromatography with UV-Vis detector coupled to inductively coupled plasma mass spectrometry (SEC-AE-UV-Vis-ICP-MS). The results showed a single fraction containing V associated with a biomolecule in the range of 8 to 16 kDa, with isoeletric points above 8. The preliminary analyses using matrix-assisted laser desorption-ionization-time of flight (MALDI-TOF) do not permit to identify such biomolecule, considering the broader size range of the proteins obtained.

Variações temporais do material particulado inalável fino e grosso e íons inorgânicos solúveis em São José dos Campos, SP

PM2,5 and PM2,5-10 samples were collected at Sao Jose dos Campos (Sao Paulo) from February 2004 to February 2005. During this time there were two periods of drought, one lasting for 25 consecutive days and a second one for 38 days. The later exhibited higher PM concentrations values than the first one. Data were divided into two groups, one comprising all measurements carried out during the 63 days without rain (dry period) and a second one comprising the remaining data (regular period). The PM2,5 and PM2,5-10 average concentrations were respectively 23 ± 7.5 and 19 ± 7.9 µg m-3 during dry period and 14 ± 7.9 and 13 ± 7.9 µg m-3 during regular period. There was a day-of-week variation with highest average concentrations on Wednesday (PM2.5) and Thursday (PM2.5-10) and lowest on Sunday. The PM2,5-10 exhibited the most pronounced variation suggesting an association with vehicular emissions. During both dry and regular periods, average SO4-2 and NH4+ concentrations were about 5 times higher in the fine than in the coarse fraction. PM2,5 ionic concentrations, especially that of K+, were higher in the dry period compared to regular one (except for Cl-, Na+ and Mg2+). Hierarchical cluster analysis and backward air mass trajectories indicate that during the dry period NO3-, SO42-, NH4+ and K+ associated with PM2.5 are significantly influenced by continental sources.

Determination of Metallothioneins and Phytochelatins using HPLC-ICPMS

Metallothioneins and phytochelatins are peptides and proteins associated with metals present in all biological systems. Generally, in the presence of certain metal concentration, they are produced naturally by the body. There are several applications including their use as indicators of environmental pollution and to fight disease. For the determination of metallothioneins and phytochelatins is necessary to use a very detailed chemical analysis procedure that involves the extraction of these complexes, followed by a methodology of separation or purification of compounds extracted and finally by the detection of both the organic compound (the protein) and the metal associated with it. Different strategies should be used whether the subject of the analysis is the apo-form of the biomolecule or the metallic complex. In the second case, special care has to be taken for preserving the metal-biomolecule association along the sample preparation procedure. UV-VIS absorbance, fluorescence or mass spectrometry are often used for detection of the biomolecules. In the case of metallic complexes, high performance liquid chromatography (HPLC High Resolution Liquid Chromatography) is the most used technique for separation, associated to mass spectrometry with inductively coupled plasma (ICP-MS Inductively Coupled Plasma Mass Spectrometry), an elemental technique, that allows the detection of metallic ions. Some aspects of this technique and its application are described in this paper.