Flow analysis-hydride generation-gas phase derivative molecular absorption spectrophotometric determination of antimony in antileishmanial drugs

In the present work, the development of a method based on the coupling of flow analysis (FA), hydride generation (HG), and derivative molecular absorption spectrophotometry (D-EAM) in gas phase (GP), is described in order to determine total antimony in antileishmanial products. Second derivative order (D²224nm) of the absorption spectrum (190 - 300 nm) is utilized as measurement criterion. Each one of the parameters involved in the development of the proposed method was examined and optimized. The utilization of the EAM in GP as detection system in a continuous mode instead of atomic absorption spectrometry represents the great potential of the analytic proposal.

Avaliação da contaminação do Igarapé do Sabino (Bacia do Rio Tibiri) por metais pesados, originados dos resíduos e efluentes do Aterro da Ribeira, em São Luís, Maranhão

This work aimed to carry out an environmental monitoring in sabino narrow river (affluent of Tibiri Basin, in São Luís - MA, Brazil), in order to verify the main environmental impacts caused by effluent residues from Ribeira landfill. Chemical analysis and bibliographic and cartographic researches on this ecosystem were also carried out. In addition, heavy metals, such as Hg, Pb and Zn, were investigated in water samples by ICP-MS technique. It was observed that the contents of such heavy metals were above the tolerance limits established by the Brazilian legislation, showing a strong impact level on the evaluated ecosystem.

Estudo da especiação de arsênio inorgânico e determinação de arsênio total no monitoramento ambiental da qualidade de águas subterrâneas

This work reports an alternative, fast and robust method, for the determination of total As, As(III) and As(V) by HG-AAS without the use of prereductants. The method is based on the different rates of arsine formation of the inorganic As species and the effect of As(III) in the signal obtained for total As. Groundwater and mineral spiked waters were used to sample preservation evaluation. The method was validated by the determination of As in SRM 1640 and used in the determination of total As and its inorganic species in groundwater samples collected from mines in the Iron Quadrangle - MG.

Emissões naturais e antrópicas de metais e nutrientes para a bacia inferior do rio de contas, Bahia

Emission factors of anthropogenic activities and natural processes were used to estimate nutrients and metals loads to the Contas River lower basin, Southern Bahia, Brazil. Among natural sources, emission from soil leaching is larger for N, Cu and Pb. Atmospheric deposition is the major natural source of P, Zn, Cd and Hg. Among anthropogenic sources, agriculture is the major source of N, Cu and P. Urban sources are the major contributors to the other elements. Present anthropogenic land uses are already responsible for 78 and 99% of total N and P loads and about 50% of total Cu and Hg.

Comportamento do mercúrio em perfis de solos do sítio Ilha de Terra-Caxiuanã, Pará

Behavior of mercury in soil profiles with archaeological black earth (ABE) and surroundings area (SA) from Sítio Ilha de Terra, Caxiuanã, can provide information on anthropogenic activity of the Amazonian habitat. The samples of ABE and SA soil profiles were submitted to mineralogical chemical (total and sequential) analysis. The data show that the Hg occurs mainly in goethite and kaolinite in the two soil profiles. The highest concentrations of Hg and Fe are observed in the SA profile. These results indicate that the prehistoric human occupation contributed to the decrease of the concentration of Hg in soil ABE from Caxiuanã.

Síntese e caracterização estrutural do ligante isatina-3-(N4-benziltiossemicarbazona) e do seu complexo de mercúrio(II)

The reaction of 4-(phenyl)thiosemicarbazide with isatin yielded a new ligand, isatin-3-(N4-benzylthiosemicarbazone). Isatin-3-(N4-benzylthiosemicarbazone) deprotonated in ethanol/KOH reacts with an ethanolic solution of Hg(NO3)2 to give a mercury complex. The compounds were characterized by IR and X-ray single crystal structure determination. The X-ray studies revealed that the complex possesses a tetrahedral geometry with two deprotonated thiosemicarbazone ligands coordenated. The ligand and its mercury complex crystallize in the monoclinic (P2(1)/c) and triclinic (P-1) crystal system, respectively.

Poluição por mercúrio em aterros urbanos do período colonial no extremo sul do Brasil

Land reclamation fills in the city of Rio Grande (RS) are polluted by mercury with concentrations ranging from 0.3 to 18.7 mg kg-1. The level of Hg pollution decreases from the oldest landfills of 18th century to recent ones. Mercury distribution along vertical profiles resembles the same for copper, lead, and zinc, what allow supposing that mercury distribution has an autochthonous character. It is suggested that the principal source of mercury pollution was the activities related to animal skin and fair hair treatment, using ancient technology known as "carroting". Similar scenario of environmental risk could be met in other Brazilian cities with similar colonization history.

Recovery of manganese and zinc from spent Zn-C and alkaline batteries in acidic medium

The anode and the internal paste of spent Zn-C and alkaline batteries were leached with 2 mol L-1 H2SO4 at 80 ºC for 2 h. Solid/liquid ratio was 1/10 (g mL-1). The leachate was treated with Na2S in order to precipitate Hg, Cd and Pb. Zn was quantitatively isolated at pH 1,5-2 by adding Na2S. Mn can be precipitated at pH close to 7. Na2S may be replaced by oxalic acid. Zn precipitated at pH around 0, whereas Mn was quantitatively recovered at pH > 4. Acidity control is a critical parameter. Na2SO4 and carbon are the end products.

Isolamento e seleção de micro-organismos resistentes e capazes de volatilizar mercúrio

Mercury (Hg) occurs in the environment as a natural and anthropogenic element, and through the years the accumulation of mercury has affected the integrity of ecosystems and human health. This study presents a screening of microorganisms resistant to organic and inorganic mercury, the determination of the minimum inhibitory concentration of Hg, the estimation of the mercury volatilization by selected microorganisms and the dynamics of volatilization. Eight Gram-negative bacteria resistant to high concentrations of mercury (60 to 210 mg L-1) were selected, and these isolates showed ability to volatilize the metal. The dynamics of the volatilization of the Proteus mirabilis M50C demonstrated that in only 4 h of incubation it was possible to volatilize 72% of the mercury present in the culture. The results showed promising application for bioremediation strategies.

Série histórica da composição química de pilhas alcalinas e zinco-carbono fabricadas entre 1991 e 2009

Mn, Zn, Fe, Cd, Pb and Hg were determined in Zn-C and alkaline batteries manufactured along almost 20 years. After samples disassembly the electroactive components were treated with aqua regia in bath ice for 24 h. Metals were analyzed by ICP-OES. Zn and Mn amounts did not vary significantly. Fe amount decreased, specially after 2000. Hg, Cd and Pb amounts dramatically decreased along time, being virtually absent in alkaline batteries manufactured after 2005. Pb still remains in Zn-C samples. Scanning electron microscopy of batteries manufactured in 1997 and 1998 showed the presence of Bi, In and Cr in the plastic/paper anode-cathode separator.

Organic and total mercury determination in sediments by cold vapor atomic absorption spectrometry: methodology validation and uncertainty measurements

The purpose of the present study was to validate a method for organic Hg determination in sediment. The procedure for organic Hg was adapted from literature, where the organomercurial compounds were extracted with dichloromethane in acid medium and subsequent destruction of organic compounds by bromine chloride. Total Hg was performed according to 3051A USEPA methodology. Mercury quantification for both methodologies was then performed by CVAAS. Methodology validation was verified by analyzing certified reference materials for total Hg and methylmercury. The uncertainties for both methodologies were calculated. The quantification limit of 3.3 µg kg-1 was found for organic Hg by CVAAS.

Simulação do intemperismo natural de pilhas zinco-carbono e alcalinas

Spent alkaline and Zn-C batteries were placed in seawater, rainwater or landfill leachate at room temperature for up 30 days in order to simulate natural weathering. After the experiments pH and electrical conductivity of the liquid were measured. The precipitate formed and the filtrate were submitted to metal analysis by ICP-OES. Seawater is the most corrosive medium, followed by landfill leachate. Pb, Cd and Hg were mainly in the filtrate. Fe, Mn and Zn were generally dominant in the precipitate. Na and K account for the electrical conductivity and are good indicators of the corrosion stage of the batteries.

Coeficientes de difusão de metais em materiais não convencionais (agarose e acetato de celulose) usados na técnica de difusão em filmes finos por gradientes de concentração

The DGT technique allows one to measure quantitatively free and labile metal species in aquatic systems. Nevertheless, for this approach, knowledge is required of the diffusion coefficients of the analytes in a diffusive layer. In this study, the diffusion coefficients of Hg(II), As(III), Mn(II), Mg(II), Cu(II), Cd(II) were determined in agarose gel and those of Ba(II), Cd(II), Cu(II), Mg(II), Mn(II) e Zn(II) in cellulose acetate membranes. These materials presented good performance and the reported results can be used as a data base for further DGT studies.

Estudo voltamétrico de redissolução catódica de cefaloglicina em meio aquoso sobre eletrodo de mercúrio

Voltamogramas de redissolução catódica de cefaloglicina em meio ácido exibem uma única onda de redução em potenciais próximos da descarga do eletrólito (-1.0 V). Entretanto, o fármaco pode ser determinado indiretamente em meio alcalino (pH 10) através do complexo formado entre cefaloglicina e Hg(I) gerado na superfície do eletrodo sob potencial de acúmulo positivo (Eac= +0.20 V). Uma curva de calibração linear no intervalo de 0.122 a 1.22 mg/mL foi obtida para cefaloglicina em tampão B-R pH 10 utilizando-se tempo de acúmulo de 30 seg e potencial de acúmulo de +0.20 V. O método mostra alta reprodutibilidade e sensibilidade com desvio padrão relativo de 1,4 % para 5 determinações de 5x10-7 mol/L de cefaclor e limite de detecção de 5,17 ng/mL.

Potencialidades analíticas do dietilditiofosfato de amônio em espectrometria de massas com plasma indutivamente acoplado empregando extração em fase sólida e sistemas de injeção em fluxo

Um sistema de injeção em fluxo envolvendo complexação com dietilditiofosfato de amônio e sorção de complexos metálicos em minicolunas de sílica gel modificada por grupos octadecil C18 é proposto para determinações multielementares em espectrometria de massa com plasma indutivamente acoplado. Influência da concentração de reagentes, natureza do ácido, tempo de reação, tempos de comutação, vazões e interferência de sódio foram investigadas. Água ou solução 2% v/v HNO3 podem ser utilizadas para lavar a coluna antes da eluição dos analitos com etanol. Amostras contendo 5000 mg Na L-1 e analisadas diretamente com o sistema proposto produzem uma concentração aparente de 63Cu de 0,45 µg L-1; por outro lado não foi observada interferência para As, Pb, Bi, Se, In, Tl, Cd, Hg e 65Cu. Para 0,25 % w/v NH4DTP e 3 mL de solução de amostra, curvas analíticas para Bi, Cu, Pb, As, Se, In, Tl, Cd, Hg no intervalo de 0,10 a 2,00 µg L-1 podem ser construídas com boas correlações (r2 > 0.998). A velocidade analítica e sensibilidade podem ser melhoradas pois dependem das condições de pré-concentração e eluição selecionadas. Com os parâmetros acima fixados, limites de detecção de 0.014 (Cu), 0.027 (As), 0.06 (Se), 0.02 (Cd), 0.029 (In), 0.043 (Hg), 0.02 (Tl), 0.06 (Pb) e 0.002 µg L-1 (Bi) foram obtidos.