Anderson Schwingel Ribeiro

Bio: Anderson Schwingel Ribeiro is an academic researcher from Universidade Federal de Pelotas. The author has contributed to research in topics: Certified reference materials & Sample preparation. The author has an hindex of 19, co-authored 83 publications receiving 1191 citations. Previous affiliations of Anderson Schwingel Ribeiro include State University of Campinas & Universidade Federal de Santa Catarina.

Determination of total mercury and methylmercury in biological samples by photochemical vapor generation.

Abstract: Cold vapor atomic absorption spectrometry (CV-AAS) based on photochemical reduction by exposure to UV radiation is described for the determination of methylmercury and total mercury in biological samples. Two approaches were investigated: (a) tissues were digested in either formic acid or tetramethylammonium hydroxide (TMAH), and total mercury was determined following reduction of both species by exposure of the solution to UV irradiation; (b) tissues were solubilized in TMAH, diluted to a final concentration of 0.125% m/v TMAH by addition of 10% v/v acetic acid and CH3Hg+ was selectively quantitated, or the initial digests were diluted to 0.125% m/v TMAH by addition of deionized water, adjusted to pH 0.3 by addition of HCl and CH3Hg+ was selectively quantitated. For each case, the optimum conditions for photochemical vapor generation (photo-CVG) were investigated. The photochemical reduction efficiency was estimated to be ∼95% by comparing the response with traditional SnCl2 chemical reduction. The method was validated by analysis of several biological Certified Reference Materials, DORM-1, DORM-2, DOLT-2 and DOLT-3, using calibration against aqueous solutions of Hg2+; results showed good agreement with the certified values for total and methylmercury in all cases. Limits of detection of 6 ng/g for total mercury using formic acid, 8 ng/g for total mercury and 10 ng/g for methylmercury using TMAH were obtained. The proposed methodology is sensitive, simple and inexpensive, and promotes “green” chemistry. The potential for application to other sample types and analytes is evident.

Determination of Trace Elements in Vegetable Oils and Biodiesel by Atomic Spectrometric Techniques—A Review

Abstract: The determination of trace elements in edible oils and biodiesel using atomic spectrometric methods is reviewed. Problems related to sample pretreatment for appropriate sample introduction and calibration are addressed as well as the strategies to overcome them. Recent trends aimed at simplifying sample manipulation are presented. The applications and scope of atomic absorption spectrometry (AAS), flame optical emission spectrometry (F-OES), inductively coupled plasma–optical emission spectrometry (ICP-OES), and inductively coupled plasma–mass spectrometry (ICP-MS) techniques for the determination of trace metals in edible oils and biodiesel are discussed, as well as some current instrumental new developments.

Determination of inorganic and total mercury in biological samples treated with tetramethylammonium hydroxide by cold vapor atomic absorption spectrometry using different temperatures in the quartz cell

Abstract: A very simple procedure is proposed for the determination of total and inorganic Hg in biological materials. Organic Hg (methylmercury) can be obtained from the difference. After treating the sample at room temperature with tetramethylammonium hydroxide (TMAH), inorganic Hg is obtained by cold vapor atomic absorption spectrometry (CV-AAS), keeping the quartz cell at room temperature, while total Hg is obtained by the same technique, heating the quartz cell in an air–acetylene flame. By analyzing several biological certified materials, it was evident that the difference between the mentioned concentrations corresponds to methylmercury. Cold vapor graphite furnace atomic absorption spectrometry (CV-GF-AAS) with retention of the vapor in a heated Au-treated graphite tube was used to optimize the vapor generation conditions and also to determine total Hg. In a general way, the concentrations obtained by both techniques were in agreement with the certified values or with differences of the certified values for total, Hg2+ and CH3Hg+, according to the t-test for a 95% confidence level. Total Hg results obtained by the two techniques were also in agreement. The relative standard deviations were lower than 10% for most of the results. The detection limits in the sample were: 0.13 μg g−1 for total Hg and 0.025 μg g−1 for Hg2+ by CV-AAS. The detection limit for total Hg by CV-GF-AAS was 0.001 μg g−1. It is amazing how this very simple method is able to provide very important information on mercury speciation.

Analysis of Powdered Coffee and Milk by ICP OES after Sample Treatment with Tetramethylammonium Hydroxide

Abstract: A simple method for the solubilization of powdered milk and soluble coffee using tetramethylammonium hydroxide (TMAH) is proposed. While 500 µL of the reagent was used for the solubilization of 350 mg of coffee samples, milk samples required 1000 µL of TMAH. Solubilization at 80 °C takes place within 10, 20 and 30 min for soluble coffee, whole and skim powdered milk, respectively. Subsequently, the volume was topped up to 25 mL with deionized water. Thereafter, the concentrations of Ca, Cu, Fe, K, Mg, Mn, Na, P, Se, Sn and Zn were determined by inductively coupled plasma optical emission spectrometry (ICP OES). When applied to standard reference material and to commercial samples the proposed method showed good results, and it was also compared with two other preparation methods. Limits of detection calculated for Ca, Cu, Fe, K, Mg, Mn, Na, P, Se, Sn and Zn were 2.1, 0.065, 0.11, 103, 0.088, 0.011, 1.5, 2.1, 1.1, 0.66 and 0.11 µg g−1, respectively. The RSD values were less than 10% for the certified reference materials (IAEA A-11 and BCR 63R). Statistical tests showed that the results for the metal concentrations do not vary significantly with the different methods or with the certified reference values, considering a confidence limit of 95%.

A standardised static in vitro digestion method suitable for food – an international consensus

Abstract: Simulated gastro-intestinal digestion is widely employed in many fields of food and nutritional sciences, as conducting human trials are often costly, resource intensive, and ethically disputable. As a consequence, in vitro alternatives that determine endpoints such as the bioaccessibility of nutrients and non-nutrients or the digestibility of macronutrients (e.g. lipids, proteins and carbohydrates) are used for screening and building new hypotheses. Various digestion models have been proposed, often impeding the possibility to compare results across research teams. For example, a large variety of enzymes from different sources such as of porcine, rabbit or human origin have been used, differing in their activity and characterization. Differences in pH, mineral type, ionic strength and digestion time, which alter enzyme activity and other phenomena, may also considerably alter results. Other parameters such as the presence of phospholipids, individual enzymes such as gastric lipase and digestive emulsifiers vs. their mixtures (e.g. pancreatin and bile salts), and the ratio of food bolus to digestive fluids, have also been discussed at length. In the present consensus paper, within the COST Infogest network, we propose a general standardised and practical static digestion method based on physiologically relevant conditions that can be applied for various endpoints, which may be amended to accommodate further specific requirements. A frameset of parameters including the oral, gastric and small intestinal digestion are outlined and their relevance discussed in relation to available in vivo data and enzymes. This consensus paper will give a detailed protocol and a line-by-line, guidance, recommendations and justifications but also limitation of the proposed model. This harmonised static, in vitro digestion method for food should aid the production of more comparable data in the future.

Determination of the bioactive compounds, antioxidant activity and chemical composition of Brazilian blackberry, red raspberry, strawberry, blueberry and sweet cherry fruits

Abstract: This study aimed to evaluate the chemical composition, identify the bioactive compounds and measure the antioxidant activity present in blackberry, red raspberry, strawberry, sweet cherry and blueberry fruits produced in the subtropical areas of Brazil and to verify that the chemical properties of these fruit are similar when compared to the temperate production zones. Compared with berries and cherries grown in temperate climates, the centesimal composition and physical chemical characteristics found in the Brazilian berries and cherries are in agreement with data from the literature. For the mineral composition, the analyzed fruits presented lower concentrations of P, K, Ca, Mg and Zn and higher levels of Fe. The values found for the bioactive compounds generally fit the ranges reported in the literature with minor differences. The greatest difference was found in relation to ascorbic acid, as all fruits analyzed showed levels well above those found in the literature.

The Science And Engineering Of Materials

Abstract: Thank you for downloading the science and engineering of materials. Maybe you have knowledge that, people have search hundreds times for their chosen readings like this the science and engineering of materials, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some malicious bugs inside their desktop computer. the science and engineering of materials is available in our book collection an online access to it is set as public so you can download it instantly. Our book servers hosts in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the the science and engineering of materials is universally compatible with any devices to read.