The Mundaú lagoon (Maceió, AL), besides being relevant socially, economically, and culturally, also in its surroundings, presents an intense anthropic occupation, characterized by a large population and the industrial activities presence. In this systematic environmental monitoring study (from 2017 to 2019), concentrations of Al, As, Bi, Cd, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Sb, Sn, V, and Zn in surface waters, and total Hg content in the bivalve Mytella charruana (sururu) were recorded, using cold vapor atomic fluorescence spectrometry (or hydride generation) (HG/CV AFS), inductively coupled plasma mass spectrometry (ICP-MS), and chronopotentiometry. In the water samples, the following elements presented concentrations above the values recommended by the National Council for the Environment (CONAMA), in µg L−1: Al (24.4−2008), Cu (1.88-13.03), Fe (84.9-4107), Hg (<0.0069-2.92), Mn (10.65-200), Pb (192-1443) and Zn (121-997), and therefore, the water was classified following the water pollution index (WPI), as highly impure and polluted. The Hg content in sururu, the main food in Mundaú lagoon, ranged from 0.036-0.63 mg kg−1 (dry weight). Further, the chemometric evaluation of the data based on the principal component and correlation analysis suggested a chemical-defined profile at the different sampling points.

This study aims at identifying and discriminating gunshot residue (GSR) from conventional ammunition of six different calibers by total reflection X-ray fluorescence (TXRF) and pattern recognition by principal component analysis (PCA). GSR samples were collected from hands of volunteer shooters with swabs moistened with deionized water and were extracted with 5% v v-1 nitric acid. Aliquots were deposited on quartz disks for further determination by TXRF of the elements Al, S, Ca, K, Mn, Fe, Ni, Cu, Zn, Br, Sr, Sb, Ba and Pb, whose concentrations were imported into the MATLAB® software for PCA execution. The method proved to be adequate for identification of one- and three-shot residue inorganic components from .40, 9 mm, .380, .38 and .308 calibers, and of three-shot residues from .32 caliber, as well as for sample discrimination as a function of the conventional ammunition calibers studied.

In this work, Ricinus communis L. press cake waste from biodiesel production was used to produce a versatile reactive material for environmental applications. The biodiesel cake waste was impregnated with FeIII at different concentrations (19-45 wt.%) and treated at 400, 600 and 800 °C. Mössbauer, X-ray diffraction (XRD), thermogravimetric analysis (TG/DTA), scanning electron microscope (SEM), elemental analysis CHN, Raman, potentiometric titration, saturation magnetization and Brunauer-Emmett-Teller (BET) analyses showed that the materials prepared at 400 °C are composed mainly of a graphitic and amorphous carbon containing dispersed magnetite (Fe3O4). At higher temperatures, metallic iron (Fe0) and iron carbide (Fe3C) are the predominant phases well dispersed in the carbon porous structure. These reduced iron species, Fe3O4 and Fe0, are active for the reduction of different hazardous contaminants. Preliminary experiments showed very high activities for the reduction and removal of aqueous CrVI.

Elementos terras raras (ETR) fazem parte de um grupo peculiar de elementos químicos e sua determinação em amostras geológicas é importante e complexa, devido às baixas concentrações e problemas com interferências espectrais e não espectrais. Neste trabalho, planejamentos experimentais foram utilizados para otimizar as condições operacionais de um espectrômetro de emissão óptica com plasma indutivamente acoplado (ICP OES) para a determinação de ETR. A razão entre o sinal analítico dos ETR e o sinal de fundo (SBR) e a razão Mg II/Mg I foram avaliadas como respostas na otimização. De acordo com os resultados obtidos, três diferentes condições de operação foram selecionadas e classificadas como robusta, semi-robusta e melhor SBR. Limites de detecção (LOD), SBR e desvio padrão relativo de medidas de uma solução do branco (DPRbranco) foram determinados. Na condição semi-robusta (potência de 1250 W e vazão do gás nebulizador de 0,90 L min-1) foram obtidos LOD e DPRbranco mais baixos que nas outras condições estabelecidas.

Rare earth elements (REEs) is a peculiar group of chemical elements. Their determination in geological samples is important and complex due to their low concentrations and problems with spectral and non-spectral interferences. Herein, the operating conditions of an inductively coupled plasma optical emission spectrometer were optimized for the determination of REEs using experimental designs. The signal-to-background ratio (SBR) of the REEs emission signals and the Mg II/Mg I line intensity ratio were evaluated as response functions. According to the results obtained, three different sets of operating conditions were selected and classified as robust, semi‑robust and best SBR conditions. Limits of detection (LOD), SBR and relative standard deviation of the blank solution (RSDblank) were determined. The semi-robust condition (RF power of 1250 W and nebulizer gas flow rate of 0.90 L min-1) exhibited lower LOD and RSDblank than others tested operating conditions.

A ozonólise do etinilestradiol (1), um hormônio sintético esteroidal, numa solução de água/metanol foi investigada. Análises por HPLC-UV revelaram que o hormônio foi completamente consumido, tanto em pH 5 quanto 8, após um tempo reacional de 20 min. O monitoramento por espectrometria de massas com ionização electrospray no modo negativo (ESI(-)-MS) revelou o contínuo consumo de 1 (detectado em sua forma desprotonada, [1 – H]-, de m/z 295), concomitantemente com o aparecimento de produtos de oxidação. Estruturas químicas foram propostas para tais produtos com base nos dados de MS (valores de m/z) e MS/MS (padrões de fragmentação dos ânions). Estes dados, em associação com conhecimento sobre a reatividade de moléculas orgânicas frente ao ozônio em solução aquosa, foram avaliados e uma rota reacional inédita para a ozonização do etinilestradiol foi sugerida. Assim, como primeira etapa nesta sequência reacional propôs-se uma adição 1,3-dipolar do ozônio sobre o anel fenólico de 1 para gerar o produto di-hidroxilado 2 (detectado como [2 – H]- de m/z 311). A perda de acetileno como o único canal de dissociação de [2 – H]- confirmou que a hidroxilação ocorreu no anel fenólico e não na porção acetilênica de 1. Oxidações subsequentes foram propostas para explicar a formação de outros produtos, todos eles contendo o grupo funcional COOH (como verificado pela dissociação das respectivas moléculas desprotonadas através da perda característica de CO2). Os dados de ESI(-)-MS também revelaram diferenças notáveis entre as reações conduzidas em pH 5 e 8, i.e., em meios levemente ácido e básico, respectivamente.

The ozonolysis of ethinylestradiol (1), a synthetic steroidal estrogen, in an aqueous-methanolic solution was investigated. HPLC-UV analyses revealed that 1 was completely consumed after a 20 min reaction time either at pH 5 or 8. ESI(-)-MS (electrospray ionization mass spectrometry in the negative ion mode) monitoring also revealed the continuous consumption of 1 (detected as [1 – H]- of m/z 295) concomitantly with the emergence of oxidation products. Chemical structures were proposed for these products based on the data of MS and MS/MS (the m/z values and fragmentation profiles of the anionic specie, respectively). These data, in conjunction with the well-established knowledge about the reactivity of organic molecules toward ozone in aqueous solution, were evaluated and an unprecedented reaction route for the ozonation of 1 could thus be suggested. Hence, the first step in this reaction sequence was ascribed to involve a 1,3-dipolar cycloaddition of ozone at the phenolic ring of 1 yielding the di-hydroxylated product 2 (detected as [2 – H]- of m/z 311). The loss of acetylene as the unique dissociation channel for [2 – H]- thus confirmed that such hydroxylation occurred at the phenolic ring rather than the acetylenic moiety of 1. Subsequent oxidations were proposed to be the origin of a number of other products, all of them bearing the COOH functionally (this was verified by the characteristic loss of CO2 during the dissociation of the related deprotonated molecules). The ESI(-)-MS records also revealed notable differences between the reaction conducted at pH 5 and 8, i.e. at slightly acid or basic media, respectively.

A espectrometria de absorção atômica com forno tubular na chama (TS-FF-AAS) foi empregada para a determinação de Cd e Pb em diferentes tipos de amostras brasileiras de tabacos após a pré-concentração no ponto nuvem (CP) otimizada por planejamento Doehlert. Para a separação das fases no procedimento por ponto nuvem, Triton® X-114 e 2-(bromo-2-piridilazo)-5-dietilaminofenol (Br-PADAP) foram utilizados como surfactante não iônico e agente complexante, respectivamente. Cádmio e chumbo foram determinados após digestão ácida e pré-concentração por ponto nuvem, sendo que as variáveis otimizadas por planejamento Doehlert foram: volume do agente complexante, volume de Triton® X-114 e pH. Um ponto de máximo foi obtido nas superfícies de resposta para Cd e Pb. Para as determinações dos elementos por TS-FF-AAS, um volume de amostra de 50 µL foi introduzido no tubo de Ni posicionado sobre a chama, usando ar como carregador na vazão de 0,4 mL min-1. Os limites de detecção e os desvios padrão relativos após a combinação de CP e TS-FF-AAS foram de 4,0 e 13 µg kg-1 e 3,1 e 0,7% para Cd e Pb, respectivamente. A exatidão do método proposto foi avaliada realizando-se testes de adição-recuperação e empregando-se material de referência certificado (folhas de chá e folhas de pessegueiro). As recuperações variaram de 93 a 103 e 93 a 107% para Cd e Pb, respectivamente. Todos os resultados obtidos para as amostras dos materiais de referência estão em concordância com os valores certificados a um nível de confiança de 95 ou 99% aplicando-se o teste t-Student.

A thermospray flame furnace atomic absorption spectrometer (TS-FF-AAS) was employed to determine Cd and Pb in different Brazilian tobacco samples. Sample pretreatment consisted of acid decomposition and cloud point (CP) preconcentration optimized by Doehlert design. To promote phase separation in the cloud point procedure, polyoxyethylene(8) isooctylphenyl ether (Triton® X-114) and 2-(bromo-2-pyridylazo)-5-diethyl-amino-phenol (Br-PADAP) were used as a nonionic surfactant and a complexing agent, respectively. The variables of the cloud point preconcentration procedure optimized by Doehlert design were: complexing agent volume, Triton X-114 volume, and pH. A response surface maximum point was obtained for Cd and Pb. For TS-FF-AAS, a sample volume of 50 µL was introduced into the hot Ni tube using air carrier at a flow rate of 0.4 mL min-1. The limits of detection and relative standard deviations obtained for Cd and Pb when CP and TS-FF-AAS were associated were 4.0 and 13 µg kg-1, and 3.1 and 0.7%, respectively. Accuracy was checked by addition-recovery experiments, as well as by using two certified reference materials (tea and peach leaves). Cadmium and lead recoveries ranged from 93 to 103 and 93 to 107%, respectively. All results obtained for reference materials were in agreement with certified values at 95 or 99% confidence levels by t-Student test.

Neste trabalho foi desenvolvido e validado um método quantitativo para a análise de anfetaminas e efedrinas em urina, utilizando-se anidrido acético e piridina, ambos em grau analítico, como derivatizantes. As amostras foram extraídas por extração em fase sólida (EFS), derivatizadas e em seguida analisadas por CG-EM. O método apresentou ampla faixa linear (25-1000 ng mL-1 com R² > 0,99), alta sensibilidade (LODs variando de 0,0140 a 15,33 ng mL-1 e LOQs variando de 0,0466 a 51,10 ng mL-1), bons índices de precisão (CV < 6% para intra- e inter-ensaios) e excelentes índices de recuperação (87-96%) para todos os compostos estudados. Após a validação, o método foi aplicado em análises de amostras reais de urina humana nas quais ao menos um dos analitos em estudo foi identificado previamente. Em todas as amostras, anfetaminas e efedrinas foram facilmente quantificadas mostrando que a associação de anidrido acético e piridina é uma boa opção como agente derivatizante.

A GC/MS method for the simultaneous analyses of different amphetamines and ephedrines in urine employing analytical-grade acetic anhydride/pyridine as derivatizing reagents was developed and validated. Solid-phase extraction was performed on the samples, which were then derivatizated and analyzed by GC/MS. The method showed a broad linear dynamic range (25-1000 ng mL-1 with R² > 0.99), high sensitivity (LODs of 0.0140 to 15.33 ng mL-1 and LOQs of 0.0466 to 51.10 ng mL-1), good precision (CV < 6% for intra- and inter-assays), and excellent extraction recovery (87 to 96%) for all the compounds studied. After validation, the method was applied in the analyses of real samples of human urine which were previously determined to contain at least one of such drugs. In all the samples, the amphetamines and ephedrines were promptly quantified, showing that the association of acetic anhydride and pyridine can be conveniently employed as a derivatizing agent.

O desempenho do compósito Feº/Fe3O4 na degradação dos inseticidas Thiamethoxam e Imidacloprid em solução aquosa foi avaliado. Planejamentos fatoriais foram realizados para verificar a influência das variáveis: concentração de H2O2, pH da solução e massa de compósito, em tais processos de degradação. O pH da solução foi a variável mais importante; deste modo, níveis de degradação elevados (> 90%) foram obtidos exclusivamente em soluções ácidas (pH=2). O compósito foi altamente eficiente na degradação dos inseticidas tanto na presença quanto, inesperadamente, na ausência de H2O2. Estes resultados indicaram que o compósito apresentou um comportamento ambíguo, podendo atuar como um agente oxidante ou redutor.

The performance of an innovative Feº/Fe3O4 composite to degrade the insecticides Thiamethoxam and Imidacloprid in aqueous solution was evaluated. Factorial designs were built to investigate the influence of a number of crucial variables on such degradation processes: H2O2 concentration, solution pH, and composite mass. The solution pH was the most influential variable; hence, significant degradation rates (> 90%) was accomplished exclusively in acidic solutions (pH=2). In addition, the composite was highly efficient in promoting the degradation of both insecticides either in the presence or unpredictably in the absence of H2O2. These results thus indicated that the composite possess a dual behavior, acting as either an oxidizing or a reducing agent.

Foi desenvolvido um estudo para avaliar a acumulação de Cu, Mn, Ni, Pb e Zn, em alface cultivada em Latossolo, ao qual foram adicionados compostos de resíduos sólidos urbanos provindos de uma grande cidade (Rio de Janeiro, Estado do Rio de Janeiro) e de uma pequena cidade (Coimbra, Estado de Minas Gerais). As amostras de composto foram aplicadas ao solo em doses crescentes e em diferentes tempos de contato entre o composto e o solo. Foi avaliada ainda a influência dos metais na produção de matéria fresca e seca de folhas da alface. A produção de alface aumentou com a elevação das doses dos compostos, sendo a produção máxima obtida entre 15 e 20 dias. As concentrações de metais nas folhas aumentaram com o acréscimo da dose de composto e com o tempo de contacto entre o composto e o solo, porém não atingiram os limites máximos permitidos pela Legislação Brasileira para alimentos. A aplicação do composto de Coimbra promoveu maior produção e concentrações menores dos metais na planta, em relação ao composto do Rio de Janeiro.

A study was performed to evaluate Cu, Mn, Ni, Pb, Ni and Zn accumulations in lettuce grown in an oxisol amended with composted urban solid wastes collected in Brazil from a big city (Rio de Janeiro, Rio de Janeiro State) and from a small city (Coimbra, Minas Gerais State). The compost samples were applied to the soil at increasing doses and different times of contact between compost and soil. The influence of the metals on the fresh and dry matter yield of leaves was also examined. Lettuce yield enhanced when the doses of the composts were increased and maximum yield was achieved in the cropping time between 15 and 20 days. The metal concentrations in the leaves augmented with the increase of the applied compost and with the increase of the time of contact between compost and soil. However, metal concentrations in the plant were below the maximum limits allowable by the food Brazilian legislation. The application of the compost from the smaller city resulted in increased lettuce productivity and lowest metal concentrations in the plants as compared to the results of the application of the compost from the bigger city.

Theoretical and practical aspects of the use of microwave-assisted strategies in chemistry are introduced for students using simple and safe experiments employing a domestic oven. Three procedures are proposed for evaluating the distribution of microwave radiation inside the microwave oven cavity: (1) variation of the volume of marshmallows; (2) drying of filter paper wetted with Co(II) solution, and (3) variation of water temperature, after microwave-assisted heating. These experiments establish the position with the highest incidence of microwave radiation in the oven cavity, which was chosen for the synthesis of salicylic acid acetate. This synthesis was performed in 5 min of heating and the yield was around 85%. All experiments can be carried out in a 4 h lab-session using low-cost instrumentation.

The aim of this work was to propose two different didactic experiments, which can be used in practical classes of analytical chemistry courses. More flexible experiments related to the theme, giving some options to the instructor are proposed. In this way, the Experiment 1 was divided in two parts. In the first one, the visualization of two distinct phases separation is emphasized: the rich and the poor phases in surfactant. In the second part, the metal pre-concentration (Co as example) is emphasized. The Experiment 2 has three different parts. In the first one, the complex formation is pointed out, in the second one, the pH influence is shown and in the last one, the influence of the complexation time is demonstrated.

Com o emprego de um método simples e rápido, são propostas algumas condições de otimização para a obtenção de máxima intensidade de cavitação em banhos de ultra-som. Os parâmetros estudados foram: volume de água dentro do banho, temperatura, concentração de detergente, posição vertical e horizontal dos tubos no banho, número de tubos dentro do banho, tempo de sonicação e substituição da água do banho. Os resultados obtidos para os banhos de ultra-som estudados (Neytech e Cole-Parmer) permitiram estabelecer as seguintes condições para máxima intensidade de cavitação: 1 L de água à temperatura ambiente; 0,2 % (v/v) de detergente; posição central e ao fundo do banho. Somente 1 tubo deve ser usado por vez dentro do banho durante a aplicação do ultra-som. A intensidade de cavitação foi linear com o tempo de sonicação até 10 minutos e a substituição de água durante a sonicação melhorou a reprodutibilidade. Esse sistema de troca contínua de água permite a sonicação de até 6 amostras consecutivamente sem mudanças no volume total de água.

Optimisation conditions for obtaining maximum cavitation intensity in ultrasonic baths are proposed using a simple and fast method. Parameters such as water volume, temperature, detergent concentration, horizontal and vertical positions, number of tubes in the bath, sonication time and bath water substitution were studied. The results obtained for both baths studied (Neytech and Cole-Parmer) lead to the following conditions for maximum cavitation intensity: 1 L of water at room temperature, 0.2 % (v/v) of detergent, central position on the bottom of the tank. Only one tube at a time should be used inside the bath during the ultrasound application. The cavitation intensity was linear with the sonication time up to 10 minutes and the water substitution during the sonication improved reproducibility. This system using continuous water change makes possible the sonication of 6 consecutive samples, without changes in the water volume.