Methods for the development and validation for determination of iron and zinc in human serum and hair samples by graphite furnace atomic absorption spectrometry (GF AAS) were performed. Solubilization was immediate by manual agitation in both samples with a 10 mL volume sample plus deionized water. Optimum pyrolysis and atomization temperatures were obtained by pyrolysis and atomization temperature curves in both matrices. For serum samples, the best temperatures were 1400 and 2500 °C (Fe) and 700 and 1600 °C (Zn), respectively. For hair samples, the best temperatures were 1000 and 2400 °C (Fe) and 800 and 1600 °C (Zn), respectively. Permanent modifiers and zirconium presented best the results for Zn in both matrices and for Fe in serum. Permanent modifier Nb was best for hair Zn. Serum and hair values were in agreement with the certified values for analytes and certified samples. The determined values for serum Fe and hair certified samples were 1.40 ± 0.2 and 114 ± 18 mg L-1, respectively. For Zn certified reference materials (CRMs), the certified samples values were 1720 ± 32 µg L-1 and 172 ± 5 mg kg-1. Simple, accurate and precise, this method represents a cost-effective detection protocol suitable for sample analysis for diagnosis of micronutrient malnutrition.

O objeto do presente estudo foi o desenvolvimento de metodologias alternativas para determinação direta de chumbo em amostras não digeridas de urina humana e soro, por espectrometria de absorção atômica com atomização eletrotérmica. Neste sentido algumas substâncias foram investigadas para atuarem como modificador químico. Volumes de 20 µL de amostras de urina diluídas 1 + 1, v/v e de soro 1 + 4, v/v, com HNO3 1% v/v e 0,02% v/v de cloreto de trimetilcetil amônio (CTAC) foram preparados diretamente nos copos do amostrador automático e introduzidos no forno de grafite. Para modificadores em solução foram usados 10 µL. Curvas de temperaturas de pirólise e atomização foram usadas em todas otimizações nas matrizes diluídas. Para urina, com o uso de irídio permanente (500 µg), as melhores temperaturas de pirólise e atomização foram de 900 e 1600 ºC respectivamente, com uma massa característica de 12 pg (recomendada de 10 pg), com pulsos de absorção simétricos e fundo corrigido. Amostras de urina contaminadas apresentaram recuperações entre 86 e 112%, usando Ir permanente. Analisando amostras de urina certificada, os resultados encontrados foram concordantes com os valores certificados (considerando um intervalo de confiança de 95%) para dois níveis do metal. Para soro, bons resultados foram obtidos com a mistura de Zr + Rh ou Ir + Rh como modificadores permanentes, com massas características de 9,8 e 8,1 pg respectivamente. Recuperações de amostras de soro contaminadas variaram entre 98,6 e 100,1% (Ir + Rh) e entre 93,9 e 105,2% (Zr + Rh). Em ambos os estudos de recuperação, o desvio padrão relativo (n=3) foi menor que 7%. A calibração para ambas as amostras foi feita através de curvas de calibração aquosas que apresentaram r² maior que 0,99. Os limites de detecção foram de 0,7 µg L-1 para as amostras de soro, usando Zr + Rh permanente, e de 1,0 µg L-1 para urina com irídio permanente.

The object of the present study was the development of alternative methods for the direct determination of lead in undigested samples of human urine and serum by electrothermal atomic absorption spectrometry (ET AAS). Thus, some substances have been investigated to act as chemical modifiers. Volumes of 20 µL of diluted samples, 1 + 1, v/v for urine and 1 + 4, v/v for serum, with HNO3 1% v/v and 0.02% v/v of cetil trimethyl ammonium chloride (CTAC) were prepared directly in the autosampler cups and placed into the graphite furnace. For modifiers in solutions 10 µL were used. Pyrolysis and atomization temperature curves were used in all optimizations in the matrixes diluted as exposed. For urine with permanent iridium (500 µg), the best pyrolysis and atomization temperatures were 900 and 1600 ºC, respectively, with a characteristic mass of 12 pg (recommended of 10 pg), with symmetrical absorption pulses and corrected background. Spiked urine samples presented recoveries between 86 and 112% for Ir permanent. The analysis results of certified urine samples are in agreement with certified values (95% of confidence) for two levels of the metal. For serum, good results were obtained with the mixture of Zr+Rh or Ir+Rh as permanent modifiers, with characteristic masses of 9.8 and 8.1 pg, respectively. Recoveries from spiked serum samples varied between 98.6 and 100.1% (Ir+Rh) and between 93.9 and 105.2% (Zr+Rh). In both recovery studies, the relative standard deviation (n=3) was lower than 7%. Calibration for both samples were made with aqueous calibration curves and presented r² higher than 0.99. The limits of detection were 0.7 µg L-1 for serum samples, with Zr+Rh permanent, and 1.0 µg L-1 for urine with iridium permanent.

Objetivou-se analisar o efeito de suplementação energética sobre o consumo e a fermentação ruminal de proteínas em dois níveis de proteína dietética (6 e 20%). Quatro novilhos mestiços fistulados no rúmen foram utilizados em um quadrado latino e os tratamentos arranjados em um fatorial 2 × 2, em que as dietas testadas constituíram-se de: A. só feno; B. feno + 2,8 kg de farelo de soja; C. feno + 2,8 kg de fubá de milho; e D. feno + 2,8 kg de farelo de soja + 2,8 kg de fubá de milho. Foram realizados quatro períodos experimentais constituídos de 18 dias, sendo sete dias para adaptação dos animais, sete dias para determinação do consumo de matéria seca e quatro dias para coleta de amostras. As coletas foram feitas através de fístula ruminal nos tempos zero, dois, quatro e seis horas após a alimentação, sendo utilizadas para determinações das concentrações de amônia, pH e AGV do líquido ruminal. Não houve interações entre o fubá de milho e o farelo de soja, assim como não ocorreu efeito do tempo de coleta sobre os parâmetros estudados. O farelo de soja reduziu a relação acetato:propionato (A:P) em 13%, aumentou o consumo de matéria seca total (CMSt) em 41,2%, sem alterar o consumo de forragem e o pH, e aumentou as concentrações de amônia (790%), propionato (48%), AGV total (39%), isobutirato (165%), isovalerato (208%) e valerato (201%). O fubá de milho não afetou a fermentação de proteína, embora tenha causado aumento no CMSt (35%) e decréscimo no pH ruminal (6%) e na relação A:P (18%).

The objective was to evaluate the effect of energetic supplementation on feed intake and ruminal fermentation of proteins in two protein levels in the diet (6 and 20%). There were used four rumen fistulated crossbred steers in a Latim square and the treatments were arranjed in a 2 × 2 factorial, in which the combinations were: A. only hay; B. hay + 2.8 kg of soybean meal; C. hay + 2.8 kg of corn meal; and D. hay + 2.8 kg of soybean meal + 2.8 kg of corn meal. Four experimental periods of 18 days were used, in which seven was for adaptation, seven for determination of dry matter intake and four for sampling. Ruminal samples were collected at 0, 2, 4 and 6 hours after feeding for determination of ammonia, pH and VFA. There was no interaction between corn meal and soybean meal, as well as no sampling time effect on the evaluated parameters. Soybean meal decreased 13% acetate:propionate (A:P) ratio and increased 41.2% DMI, with no effect on forage intake and pH and increased ammonia (790%), propionate (48%), total VFA (39%), isobutyrate (165%), isovalerate (208%) and valerate (201%). Corn meal did not affect protein fermentation, although it caused increase in DMI (35%) and decrease in ruminal pH (6%) and A:P ratio (18%).

An automatic system for the direct determination of lead and tin by atomic absorption spectrometry is described. The on-line treatment of the metallic samples was obtained by anodic electrodissolution in a flow injection system. Lead was determined by flame atomic absorption spectrometry (FAAS) and tin by graphite furnace atomic absorption spectrometry (GFAAS). A computer program managed the current source and the solenoid valves that direct the fluids. Good linear correlations between absorbance and current intensity for lead and tin were observed. Results were in agreement with the certified values. Precision was always better than 5%. The recommended procedure allows the direct determination of 60 or 30 elements/h using FAAS or GFAAS, respectively.

An automatic dispenser based on a flow-injection system used to introduce sample and analytical solution into an inductively coupled plasma mass spectrometer through a spray chamber is proposed. Analytical curves were constructed after the injection of 20 to 750 µL aliquots of a multielement standard solution (20.0 µg L-1 in Li, Be, Al, V, Cr, Mn, Ni, Co, Cu, Zn, As, Se, Sr, Ag, Cd, Ba, Tl, Pb) and the acquisition of the integrated transient signals. The linear concentration range could be extended to ca. five decades. The performance of the system was checked by analyzing a NIST 1643d reference material. Accuracy could be improved by the proper selection of the injected volume. Besides good precision (r.s.d. < 2%), the results obtained with the proposed procedure were closer to the certified values of the reference material than those obtained by direct aspiration or by injecting 125 µL of several analytical solutions and samples.