ABSTRACT The fabrication of traditional construction materials consumes a large amount of energy, emits pollutants, and utilizes nonrenewable raw materials. Therefore, it is important to reduce the environmental impact of construction through the use of eco-friendly materials, such as bamboo. This work presents the characterization of Bambusa vulgaris, which is widely available in Brazil. The aim is to employ this raw material as a construction material. The geometric and physical properties were obtained. The results showed that, when bamboo is soaked in water, dimensional variations up to 7% were observed along the radial direction. The mechanical properties depend on the moisture content. The compressive strength can exceed 60 MPa with approximately 7% moisture content, while the tensile strength can exceed 100 MPa.

This work describes a procedure for determination of Cd, Ni and V in spices by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) using direct solid sampling (SS). The use of Pd/Mg(NO3)2 as modifier for Cd, and an additional air-assisted pyrolysis step allowed the use of aqueous calibration for all analytes. Accuracy was checked by analysis of certified reference materials (CRMs) and the results were in agreement to certified values at 95% confidence level (t-test). Eight samples of spices were analyzed by the proposed procedure and by inductively coupled plasma mass spectrometry (ICP-MS). The found concentrations were 88-233 ng g-1 Cd , 113-2842 ng g-1 Ni and 154-1007 ng g-1 V, with precision generally better than 12%. Results obtained by the proposed procedure were in agreement with those obtained by microwave-assisted digestion and ICP-MS determination. The limits of detection were 0.2, 18 and 7 ng g-1 for Cd, Ni and V, respectively.

Bismuth was evaluated as internal standard for Pb determinations and showed usefulness to minimize variations due to changes in the experimental conditions of the inductively coupled plasma optical emission spectrometry (ICP OES), inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). Thirty four samples were analyzed and the Pb contents obtained by ICP-MS and ETV-ICP-MS were in agreement at 95% confidence level. Plant, biological tissue and soil reference materials were also analyzed and the results were close to certified values upon the use of the internal standard. Recoveries for Pb spikes (ICP OES: 95-110%; ICP-MS: 95-106%; ETV-ICP-MS: 92-119%) were better than those obtained with external calibration (ICP OES: 56-91%; ICP-MS: 36-136%; ETV‑ICP-MS: 5-123%). The relative standard deviations (n = 12) was improved from 1-9% to 0.2-6% (ICP OES), from 0.5-11% to 0.1-7% (ICP-MS) and from 0.4-7% to 0.1-4% (ETV‑ICP‑MS) by using external and internal standard calibrations, respectively.

A espectrometria de absorção atômica em forno de grafite de alta resolução com fonte contínua (HR-CS GF AAS) é proposta para determinar Pb em sombra de olho e blush empregando a análise direta de sólidos. O emprego da mistura de modificadores químicos Pd(NO3)2 + Mg(NO3)2 possibilitou a calibração aquosa de 0,25 a 2,5 ng Pb (r = 0,998). O desempenho do método proposto foi avaliado por meio da análise de digeridos de sombra e de blush por espectrometria de absorção atômica em forno de grafite com fonte de linhas (LS GF AAS) como técnica comparativa. Os resultados obtidos por HR-CS GF AAS e LS GF AAS foram concordantes entre si a um nível de confiança de 95% (teste t pareado). O limite de quantificação (massa seca) foi de 0,020 ng mg–1. A concentração de Pb nas amostras de sombra de olho e de blush variou de 1,222 a 9,632 ng mg–1 e 0,362 a 28,091 ng mg–1, respectivamente.

Direct solid sampling is proposed for Pb determination in eye shadow and blush samples by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). A mixture of Pd(NO3)2 + Mg(NO3)2 was employed as chemical modifier, and aqueous calibration (0.25-2.5 ng Pb, r = 0.998) was obtained. Accuracy of the determination of Pb in eye shadow and blush samples by the proposed method was verified by line source graphite furnace AAS as a comparative technique employing digested samples. The results obtained by the two methods were in agreement at a 95% confidence level (paired t-test). The limit of quantification (dry mass) was 0.020 ng mg–1. The Pb content in the eye shadow and blush samples varied between 1.222 and 9.632 ng mg–1 and 0.362 and 28.091 ng mg–1, respectively.

Os teores de vários nutrientes foram determinados em 35 amostras de cafés verdes e torrados, por espectrometria de absorção atômica em chama (Ca, Mg, Fe, Cu, Mn e Zn), fotometria de emissão atômica em chama (Na e K) e pelo método Kjeldahl (N) após preparação das amostras por dois procedimentos de decomposição via úmida: i) sistema aberto (bloco digestor) e ii) sistema fechado (forno de microondas convencional com controle de pressão e temperatura). A exatidão dos procedimentos foi verificada analisando-se três materiais de referência certificados do National Institute of Standards and Technology (SRM 1573a Folha de Tomateiro; SRM 1547 Folha de Pessegueiro; SRM 1570a Espinafre). A análise dos dados após a aplicação do teste-t mostrou que os resultados obtidos no procedimento que empregou decomposição assistida por microondas em frascos fechados foram mais exatos do que os obtidos por bloco digestor com frascos abertos no nível de 95% de confiança. Além da exatidão, outras características favoráveis encontradas foram menores valores de branco analíticos, menor consumo de reagentes e menor tempo de decomposição das amostras. Análises exploratórias dos dados empregando-se Análise por Componentes Principais (PCA) e Análise por Agrupamentos Hierárquicos (HCA) mostraram que os elementos Na, K, Ca, Cu, Mg e Fe foram os principais responsáveis na diferenciação das amostras de cafés verde e torrado.

The contents of some nutrients in 35 Brazilian green and roasted coffee samples were determined by flame atomic absorption spectrometry (Ca, Mg, Fe, Cu, Mn, and Zn), flame atomic emission photometry (Na and K) and Kjeldahl (N) after preparing the samples by wet digestion procedures using i) a digester heating block and ii) a conventional microwave oven system with pressure and temperature control. The accuracy of the procedures was checked using three standard reference materials (National Institute of Standards and Technology, SRM 1573a Tomato Leaves, SRM 1547 Peach Leaves, SRM 1570a Trace Elements in Spinach). Analysis of data after application of t-test showed that results obtained by microwave-assisted digestion were more accurate than those obtained by block digester at 95% confidence level. Additionally to better accuracy, other favorable characteristics found were lower analytical blanks, lower reagent consumption, and shorter digestion time. Exploratory analysis of results using Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that Na, K, Ca, Cu, Mg, and Fe were the principal elements to discriminate between green and roasted coffee samples.

É proposto um procedimento para a determinação direta de vanádio em amostras de urina por espectrometria de absorção atômica com atomização eletrotérmica em forno de grafite usando injeção à quente e pré-concentração dentro do tubo de grafite. Três aliquotas de 60 µL foram injetados seqüencialmente dentro do atomizador pré-aquecido a uma temperatura de 110 ºC. As etapas de secagem e pirólise foram repetidas após cada injeção. Às amostras de urina foram adicionados o modificador químico fluoreto de bário (100 mg L-1) e o surfactante Triton X-100 (0,3% v v-1). A vazão da amostra durante a injeção dentro do tubo pré-aquecido foi de 0,5 µL s-1. Os limites de detecção e de quantificação sem pré-concentração foram, respectivamente, 0,54 e 1,82 mg L-1, e com pré-concentração 0,11 e 0,37 µg L-1. O teste de adição e recuperação foi empregado em amostras de urina para avaliar a exatidão do procedimento proposto. Os valores de recuperação obtidos variaram de 96,0 a 103,0% para as adições de 0,8 a 3,5 µg L-1 V. O procedimento proposto possibilita a determinação de vanádio sem nenhum pré-tratamento e com mínima diluição da amostra.

In this work it was developed a procedure for the determination of vanadium in urine samples by electrothermal atomic absorption spectrometry using successive injections for preconcentration into a preheated graphite tube. Three 60 µL volumes were sequentially injected into the atomizer preheated to a temperature of 110 ºC. Drying and pyrolysis steps were carried out after each injection. A chemical modifier, barium difluoride (100 mg L-1), and a surfactant, Triton X-100 (0.3% v v-1), were added to the urine sample. When injecting into a hot graphite tube, the sample flow-rate was 0.5 µL s-1. The limits of detection and quantification were 0.54 and 1.82 without preconcentration, and 0.11 and 0.37 µg L-1 with preconcentration, respectively. The accuracy of the procedure was evaluated by an addition-recovery experiment employing urine samples. Recoveries varied from 96.0 to 103% for additions ranging from 0.8 to 3.5 µg L-1 V. The developed procedure allows the determination of vanadium in urine without any sample pretreatment and with minimal dilution of the sample.

This paper describes a review on internal standardization in atomic absorption spectrometry with emphasis to the systematic and random errors in atomic absorption spectrometry and applications of internal standardization in flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry. The rules for selecting an element as internal standard, limitations of the method, and some comments about the application of internal standardization in atomic absorption spectrometry and the future of this compensation strategy are critically discussed.

A flow injection spectrophotometric system was projected for monitoring hydrogen peroxide during photodegradation of organic contaminants in photo-Fenton processes (Fe2+/H2O2/UV). Sample is injected manually in a carrier stream and then receives by confluence a 0.1 mol L-1 NH4VO3 solution in 0.5 mol L-1 H2SO4 medium. The product formed shows absorption at 446 nm which is recorded as a peak with height proportional to H2O2 concentration. The performance of the proposed system was evaluated by monitoring the consumption of H2O2 during the photodegradation of dichloroacetic acid solution by foto-Fenton reaction.

É proposto um sistema de análise química por injeção em fluxo para a deteminação espectrofotométrica de manganês em aços baseado no efeito catalítico da Ag(I) na oxidação em linha de Mn(II) a Mn(VII) sobre uma superfície eletródica de platina. Após a injeção simultânea de amostra e eletrólito na célula eletroquímica, a mistura era homogeneizada por bolhas de ar e os íons permanganatos gerados eram monitorados a 545 nm. As alturas dos sinais transientes obtidos refletiam a concentração do manganês na amostra. Foram investigados os principais parâmetros relacionados com os processos coulométricos tais como intensidade de corrente, concentração do mediador, tempo de eletrólise, natureza do eletrólito suporte, bem como aqueles relacionados com a arquitetura do sistema FIA. O sistema espectrofotométrico proposto possibilitou a determinação de manganês em aços no intervalo de concentrações de 5,00 a 150 mg L-1 (r = 0,9998). Com tempos de eletrólise de 60 s, foram possíveis 20 determinações por hora (R.S.D. < 3%). Os resultados da análise aços certificados com o sistema proposto não foram estatisticamente diferentes dos valores certificados e daqueles obtidos pelo método de referência ao nível de 95% de confiabilidade.

The aim of this work is to propose a flow spectrophotometric procedure for manganese determination in steel based on electrochemical oxidation of Mn(II) to Mn(VII) at a Pt electrode surface by means of the catalytic effect of Ag(I). The on-line oxidation step was obtained by injecting sample and electrolyte solution directly into an electrolytic cell. After electrolysis, the injectate was homogenized by bubbling air. The permanganate ions produced were passed through the spectrophotometer where absorbance was monitored at 545 nm. Effects of direct current, silver concentration, timing, flow rates, concentration and composition of support electrolyte were investigated. Direct current and silver content manifested themselves as the most relevant parameters. For determination of manganese in the 5.00 - 150 mg L-1 range (r = 0,9998) and 60 s electrolysis time, the sample throughput was 20 h-1. Accuracy was assessed by analyzing ten steel standard reference materials. Results are precise (R.S.D. < 3%) and in agreement with certified values of reference materials and with standard methods at 95% confidence level.