Search

Foi desenvolvido um metodo de preparo de amostras de pao do tipo bisnaguinha utilizando o TMAH para a solubilizacao alcalina. O objetivo desse trabalho foi avaliar a concentracao de Cu, Fe, K, Mg, Na e Zn apos a solubilizacao das amostras a temperatura ambiente, em overnight. A solubilizacao alcalina se apresentou como um metodo simples e rapido, alem de ser uma melhor alternativa frente aos procedimentos de mineralizacao convencional, permitindo a solubilizacao completa das amostras usando pequenas quantidades de TMAH. Utilizou-se um metodo de decomposicao acida e adicao de analito para avaliar a exatidao do metodo. Obtiveram-se baixos limites de deteccao 0,073; 0,051; 0,021; 0,008; 0,003 e 0,043 mg kg-1 para Cu, Fe, K, Mg, Na e Zn, respectivamente, alem de bons valores de recuperacao, variando de 80 a 120 % para os analitos. Dentre os resultados obtidos todos apresentaram concentracoes de acordo com a legislacao pra Na e abaixo do DRI para os demais mais elementos. A comparacao de metodo nao apresentou diferenca significativa, assim o metodo se mostrou adequado para as analises.

EVALUATION OF THE TOTAL CONCENTRATION AND THE BIOACCESSIBLE FRACTION OF METALS IN SAMPLES OF GRAPE SKINS OF CULTIVARS TANNAT AND CABERNET SAUVIGNON BY MIP OES. This paper describes the evaluation of the total concentration of Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Mn, Pb e Zn and the bioaccessible fraction of Ba, Cu, Fe, Mn, Pb and Zn in samples of grape skins from different cultivars (Vitis Viníferas Tannat and Cabernet Sauvignon) by MIP OES. For the determination of total concentration, acid decomposition with a reflux system adapted to the digestion tubes in the oxidizing medium of HNO3 and H2O2 were used. The accuracy of the method was verified by recovery tests, whose values ranged from 80 to 120%, as well as through a comparative method in closed system. Bi, Cd and Cr showed values for total content below the LOD or below the values acceptable for health while Pb is higher than 0.2 mg kg-1, for both cultivars. To evaluate the bioacessible fraction, the gastrointestinal system was simulated using an in vitro procedure, and its performance was assessed considering the bioaccessible fraction (supernatant) and the non-bioaccessible fraction, whose sum should be closed to the total concentration, and the results obtained were between 81 and 120%. Both cultivars showed similar values for the bioaccessible fractions (~13.5 – 53% of the total content).

This study presents information about the total concentration and bioaccessible fraction of barium (Ba), calcium (Ca), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), potassium (K), lithium (Li), magnesium (Mg), manganese (Mn), molybdenum (Mo), lead (Pb) and zinc (Zn) in different cultivars of tomato (Gaucho, Paulista, Italiano and Cherry) and their derivatives (sauce and tomato extract). The determinations were performed by microwave induced plasma optical emission spectrometry (MIP OES). The bioaccessible fraction of the elements was evaluated through in vitro digestion process and the concentrations varied between 25 and 100 % ​for Cu, Fe, Mn and Zn, depending on the type of tomato sample and its derivatives. The total concentrations for all the elements studied were below the recommendation of dietary guidelines. For Ba, only the Italiano sample presented 22 % of bioaccessibility. For Pb, the highest percentage of bioaccessible fraction was found in sauces and tomato extracts. The elements Cd, Hg, Li and Mo presented concentrations lower than the limit of detection for the bioaccessibility method.

In this work, two sample preparation procedures for subsequent determination of Na, K, Ca and Mg by techniques of atomic spectrometry in samples of Brazilian cream cheese were evaluated. The determinations were performed on two equipments, F AAS and MIP OES, which presented similar results, being evident the advantages of MIP OES since it is a multielementar technique with low operational cost and high efficiency. The first procedure was carried out by acidic decomposition (HNO3/H2SO4) in a reflux system, and the second used the alkaline solubilization with tetramethylammonium hydroxide. The accuracy was verified by recovery tests and the results were between 80 and 104% for both procedures. A comparison with a reference procedure was also performed and no significant differences have been observed at the 95% confidence level. The evaluated elements were not in accordance with the values indicated on the labels of all products, showing the importance for monitoring these products. The methods of sample preparation proposed showed to be simple, inexpensive, providing accurate and precise results, and are a promising alternative to be used for the quality control of these routine test samples.

An analytical method for the determination of mineral elements in fresh and processed meat samples using inductively coupled plasma optical emission spectrometry (ICP OES) was developed. The samples were introduced into the ICP OES equipment after alkaline sample solubilization with 25% (m/v) tetramethylammonium hydroxide for 2–3 h, at room temperature, and dilution with water. The instrumental parameters were optimized using plasma robustness and the signal-to-background ratio. The species studied were Fe, Mg, Mn, P and Zn and the accuracy of the method was evaluated by analyzing different certified reference materials (bovine liver, meat homogenate and bovine muscle); recovery percentages ranged from 85% to 118%. The results obtained showed good agreement at a confidence level of 95% with the certified values, presenting RSD values

This paper describes the optimization of a sample preparation method using response surface methodology for Al, Cd, Cu, Fe, Mg, Mn, Mo, Na, Ni and Ti determinations in samples of rice husk and rice husk ash by MIP OES. Sample preparation was performed using a reflux system adapted to the digestion tubes. This system allowed the decomposition of the samples without the necessity of replacement of the acids during this step without any loss of volatile elements. The decompositions were performed with 3.6 mL of HNO3 and 1.4 mL of H2SO4 for 205 min in a digester block at 225 ºC. The detection limit for determination of respective analytes in both samples were satisfactory. The RSDs for the analytes were less than 10%. Moreover, the accuracy of the method can be verified by recovery tests, whose values ranged from 82 to 115% for husk samples and 82 to 120% for ashes. The proposed method was presented as a simple, safe and low cost procedure being suitable for sample preparation and subsequent determination of metals by MIP OES.

This paper presents a study involving the development of a new mini polytetrafluoroethylene (PTFE) vessel project for biological sample preparation in micro scale in closed system with microwave radiation for subsequent determination of Cd, K, Mg and Na by atomic spectrometry techniques. All experiments were carried out in micro quantities of samples (up to 20 mg) and reagents (300 µL of HNO3) for 5 min at 350 W. Certified reference materials of biological samples (bovine muscle and liver) were used to evaluate the accuracy of the proposed system and the results obtained were in agreement with the certified value at 95% of confidence (t -test). Relative standard deviations (RSD) were lower than 8.0% for all elements. The proposed method is not only easy and fast, but it is also based on the use of an inexpensive system for sample digestion.

Chrysobalanus icaco L. is a medicinal plant, used to treat diabetes and dyslipidemia in Brazil. The biological effects may vary depending on the source of plant. Experiments were performed to assess these effects from plants collected in the field and those obtained from dried herbs market. Glycemia, cholesterol and triglycerides serum concentrations were measured in healthy and diabetic rats treated with aqueous extract of leaves. Diabetic rats treated with the extract showed lower serum triglycerides, but there was no significant difference (P>0.05) in glycemia and cholesterol levels, compared to the control group without diabetes. Also, the genotoxic effects of these extracts were evaluated using the comet assay in total blood cells obtained from healthy rats ingested with extracts instead of drinking water. This assay showed that the extracts from either free market or endemic area were genotoxic. However, the extract obtained from the popular market was more genotoxic than that prepared from field plants. This study demonstrates that though the extract has therapeutic property that lowers the rate of triglycerides, it is not free of deleterious effects; this calls for precaution in its use as a phytotherapeutical agent. Key words: Chrysobalanus icaco, cholesterol, comet assay, genotoxic potentiality, triglycerides, diabetes.

The aim of this study was to evaluate the performance of a reflux system adapted in the digestion tubes in sample preparation of xanthan gum for subsequent determination of Ca, Cu, K, Mg, Na and Zn by using spectrometric techniques. Through the proposed method, the samples were digested with HNO3 for 3 h in a digester block at 220 °C. The accuracy of the method was evaluated by comparing the results with another sample preparation method and by using recovery tests, which results vary between 83 and 103%. The efficiency of digestion was assessed and significant results were verified through residual carbon values, which were five times lower compared to conventional acid digestion in open system, with use of HNO3 and HClO4. The proposed methodology is a simple and accurate analytical strategy, which does not require the use of special equipment, neither a mixture of strong oxidizing acid in the sample preparation.

A simple alternative decomposition procedure for the determination of Na, K, Ca, and Mg in xanthan gum was proposed. The samples were treated in the presence of HNO 3 and HClO 4 , ensuring complete digestion. After decomposition, Na and K content were determined by flame atomic emission spectrometry and Ca and Mg content by flame atomic absorption spectrometry. The accuracy of the method was verified by comparing the results with those obtained from the conventional decomposition by calcination method, and there were no significant differences between the results at the 95% confidence level. The limits of detection in the sample were 0.011, 0.004, 0.45 and 0.001 mg g −1 for Na, K, Ca and Mg, respectively. The relative standard deviations were lower than 10%. The method proposed is simple, fast, reproducible, and requires less sample than calcinations method.

A systematic study was performed to evaluate the performance of a multiple microflame (MM) quartz tube atomizer (QTA) for minimizing interferences and to improve the extent of the calibration range using a batch system for hydride generation atomic absorption spectrometry (HG AAS). A comparison of the results with conventional QTA on the determination of antimony, arsenic, bismuth and selenium was performed. The interference of As, Bi, Se, Pb, Sn and Sb was investigated using QTA and MMQTA atomizers. Better performance was found for MMQTA, and no loss of linearity was observed up to 160 ng for Se and Sb and 80 ng for As, corresponding to an enhancement of two times for both analytes when compared to QTA (analyte mass refers to a volume of 200 μl). For Bi, the linear range was the same for QTA and MMQTA (140 ng). With the exception of Bi, the tolerance limits for hydride-forming elements were improved more than 50% in comparison to the conventional QTA system, especially for the interferences of As, Sb and Se. However, for Sn as an interferent, no difference was observed in the determination of Se and Sb using the MMQTA system. The use of MMQTA-HG AAS complied with the relatively high sensitivity of conventional QTA and also provided better performance for interferences and the linear range of calibration.

Citric acid was used as a chemical modifier for Pb determination by graphite furnace atomic absorption spectrometry in dietary supplement samples (calcium carbonate, dolomite and oyster shell samples) and its efficiency was compared to the use of palladium. Pyrolysis and atomization curves were established without use of chemical modifier, with the addition of 20, 100 and 200 μg of citric acid, and with 3 μg of palladium. The citric acid modifier made possible the interference-free Pb determination in the presence of high concentrations of Ca and Mg nitrates. Acid sample digestion involving closed vessels (microwave-assisted and conventional heating) and acid attack using polypropylene vessels at room temperature were compared. All digestion procedures presented similar results for calcium carbonate and dolomite samples. However, for oyster shell samples accurate results were obtained only with the use of closed vessel systems. Analyte addition and matrix-matched standards were used for calibration. The characteristic mass for Pb using citric acid and palladium were 16 and 25 pg, respectively. The relative standard deviation (RSD) was always less than 5% when citric acid was used. The relative and absolute limits of detection were 0.02 μg g − 1 and 8 pg with citric acid and 0.1 μg g − 1 and 44 pg with the Pd modifier, respectively ( n = 10, 3σ). The recovery of Pb in spiked calcium supplement samples (10 μg l − 1 ) was between 98% and 105%. With the use of 100 μg of citric acid as chemical modifier, problems such as high background absorption and high RSD values were minimized in comparison to the addition of 3 μg of palladium.

This paper describes the evaluation of a method for determination of Cd and Pb in xanthan gum samples by Graphite Furnace Atomic Absorption Spectrometry (GF AAS) using NH4H2PO4 as the chemical modifier. The sample preparation was performed using a reflux system adapted in the digestion tubes. With this system it was possible to increase the temperature of the digester block above the boiling point of the reaction medium, preventing loss of analyte and excessive evaporation of acids during heating. Samples were digested with HNO3 for 3 h in a digester block at 220 oC. The limits of detection for Cd and Pb were 2.2 and 33.8 ng g-1, respectively. The RSDs for both analytes were, on average, lower than 5.0% and accuracy was verified by recovery tests, yielding values in the 83-100% range.

This paper describes the evaluation of a new method of sample preparation using a cold finger system with continuous water flow for rice analysis by flame atomic absorption spectrometry. The limits of detection for Cu, Fe, Mn and Zn for the proposed method were 0.36, 1.84, 2.12 and 0.16 mg kg-1, respectively. The RSDs were lower than 6.0% for all elements and the CRM analyzed showed values with 95% agreement. The proposed method is simple and safe for the proposed objective and does not require the use of mixtures of acid or special equipment for sample preparation.

Two different sample preparation methods were evaluated for meat samples employing the solubilization in alkaline or acidic media. The aim of this study was to determine Na and K levels after sample solubilization with tetramethylammonium hydroxide (TMAH) at room temperature, and with formic acid and heating in a digester block at 50 ºC for ca. 2 h. The alkaline solubilization showed to be a simple and robust method and the better alternative in relation to the mineralization conventional procedures, allowing the complete solubilization of the samples even when small quantities of TMAH were used. The method was validated by using certified reference material as well as by comparing with samples digested with nitric acid. The limits of detection obtained were 0.8 and 2.0 μg g-1 for Na and K, respectively, and showed to be adequate for the analysis purposes. Foram avaliados dois métodos diferentes de preparo de amostras de carnes baseados na solubilização em meios alcalino ou ácido. O objetivo deste estudo foi determinar os teores de Na e K após solubilização com hidróxido de tetrametilamônio (TMAH) temperatura ambiente, e com ácido fórmico e aquecimento em bloco de digestão a 50 ºC por cerca de 2 h. A solubilização alcalina se apresentou como uma metodologia simples e robusta e a melhor alternativa frente aos procedimentos de mineralização convencional, permitindo a solubilização completa das amostras usando pequenas quantidades de TMAH. O método foi validado empregando-se materiais de referência certificada assim como pela comparação com método de digestão convencional com ácido nítrico. Os limites de detecção obtidos foram de 0,8 e 2,0 mg g-1 para Na e K, respectivamente, e se mostraram adequados para o objetivo das análises.

Um metodo simples para o tratamento de amostras de carne fresca e processada com hidroxido de tetrametilamonio (TMAH) e proposto para a determinacao de Ca, Fe e Mg por espectrometria de absorcao atomica com chama (FAAS) e Cu por espectrometria de absorcao atomica com forno de grafite (GFAAS). A exatidao foi avaliada por comparacao dos resultados usando outros dois procedimentos de preparo de amostra e por analise de materiais de referencia certificados. Nao houve diferenca significativa entre os resultados obtidos, em um nivel de confianca de 95%. Os limites de deteccao para Ca, Cu, Fe e Mg foram 45,0, 0,2, 16,0 e 0,3 µg g -1 , respectivamente. A espectrometria de absorcao atomica de alta resolucao com fonte continua em forno de grafite (HR-CS GFAAS) foi empregada para avaliar as interferencias espectrais na determinacao de Cu. Entretanto, nenhuma interferencia foi encontrada. O metodo proposto e simples, rapido e confiavel para analise de produtos carneos e nao requer o uso de equipamentos especiais nem de acidos fortes no preparo das amostras. A simple method for treating fresh and processed meat with tetramethylammonium hydroxide (TMAH) is proposed for the determination of Ca, Fe and Mg by flame atomic absorption spectrometry (FAAS) and Cu by graphite furnace atomic absorption spectrometry (GFAAS). The accuracy was evaluated by comparison of the results by using two other sample preparation procedures and by the analysis of certified reference materials. No significant differences between the results were found at the 95% confidence level. Limits of detection for Ca, Cu, Fe and Mg were 45.0, 0.2, 16.0 and 0.3 µg g -1 , respectively. High-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) was employed to evaluate the spectral interference in the determination of Cu. However, no interference was found. The proposed method is simple, fast and reliable for meat products analysis and does not require especial equipment, neither strong acid for sample preparation.

The aim of this study was to present three sample preparation methods for the determination of Cd, Pb and Sn in meat by Graphite Furnace Atomic Absorption Spectrometry (GFAAS): acid digestion, solubilization with tetramethylammonium hydroxide and formic acid. For the digestion with HNO3, a conventional open system with a cold finger was used. This system helped to avoid losses of analytes and reagents by volatilization, permitting to operate at high temperatures applied at a digester block and reducing the digestion time (∼1 h). Solubilizations were performed at room temperature. The slurry was left standing overnight and remained closed until achieving complete solubilization. The temperature program of the graphite furnace was optimized for each element in the different means of preparation samples using a mixture of Pd–Mg. The figures of merit were similar for all sample preparation methods evaluated. The limits of detection obtained for the acid digestion procedure were 0.0006, 0.0164 and 0.0520 μg g−1 for Cd, Pb and Sn, respectively. In order to evaluate the accuracy of the results obtained by the three sample preparation methods, recovery tests for four real meat samples were performed and the recoveries ranged from 93.7 to 109%, supporting the accuracy of the method. Also, different certified reference materials of meat were analyzed and the results obtained were in agreement with the certified value at 95% of confidence (t-test). The best results were obtained by the acid digestion procedure with the cold finger system. This procedure is faster, the system is semi-closed with no significant contamination or loss of analytes by volatilization and it provides a better signal/noise ratio.

A new procedure based on exposure of ethanol biofuel samples to UV radiation in the presence of low molecular weight organic acids was developed for the determination of total Hg (inorganic and organometallic species: Hg2+, CH3Hg+ and CH3CH2Hg+) by photochemical vapor generation coupled with atomic absorption spectrometry (photo-CV-AAS). For each species, the optimum conditions for photochemical generation were investigated, including the effects of medium composition, exposure time to the UV radiation and transfer gas flow rate. The accuracy was evaluated by assessing the recoveries of species-specific spikes (91–107%) as well as by assessing recovery from a mixture of all species of the mercury added to the ethanol biofuel samples based on calibration standards prepared in high purity bidistilled ethanol. The limits of detection ranged from 0.05 to 0.09 μg L−1 for all addition and recovery tests, enabling the determination of total Hg. The proposed method is sensitive, simple (no sample pretreatment) and provides a direct approach to the generation of mercury vapor from ethanol biofuel samples while promoting “green” chemistry.

This paper describes the method optimization using response surface methodology for Cu, Fe, Zn and Na determinations in coal and ash samples by spectrometry techniques. The sample preparation was performed using a recirculation system adapted in the digestion tubes. This system allowed increase of temperature in the digester block above the boiling point of the reaction medium, avoiding acid evaporation during the heating. The digestions were realized with HNO3 and H2O2 for 1 h in a digester block at 145 °C. The limits of detection for determination of Cu, Fe, Zn and Na in both samples were satisfactory. The RSD for the analytes were lower than 6.0%. Statistical tests showed that results for all analytes do not vary significantly with official method (ASTM), considering a confidence limit of 95%. Besides, the accuracy was verified by recovery tests, whose values ranged from 92.7 to 104.7% in coal, and 98.7 to 115.3% in ash.