Aline Lisbôa Medina

USE OF MIP OES AND F AAS/AES FOR DETERMINATION OF Ca, K, Na AND Mg IN BRAZILIAN CREAM CHEESE

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.

New Design of Mini PTFE Vessels for Sample Preparation in Micro Scale: Determination of Cd, K, Mg and Na in Biological Sample

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.

Evaluation of the Concentration of Cu, Zn, Pb and Cr in Different Fish Species from the São Gonçalo Channel in Pelotas-RS, Brazil

The objective of this study was to evaluate the concentration of Cu, Zn, Cr and Pb in different species of fish collected in the estuarine and limnic regions of the São Gonçalo channel, located in the Patos-Mirim lagoon complex in the coastal plain of Rio Grande do Sul State (Southern Brazil) during 2013 (autumn, winter and spring) and 2014 (summer). Fish samples were decomposed in a digester block with a reflux system under conditions optimized using a central composite design as it follows: 250 mg of fish sample, 5 mL HNO3, 2 mL H2O2 during 2 h at 150 °C. The concentrations obtained ranged from 6.7 to 12.0 mg kg for Cu; 1.8 to 23.6 mg kg for Zn; 37 to 487 μg kg for Pb; and 40 to 1268 μg kg for Cr. The highest concentrations of Cu, Zn and Pb, were observed in fishes collected at locations in the estuarine region and Cr showed high levels, especially in the limnic region. The samples of the species Loricariichthys anus (viola) showed the highest concentrations of all analytes investigated.

Beer sample decomposition using a reflux system for the monoelementar determination by F AAS/AES and multielementar determination by MIP OES

Abstract This study describes the development of an analytical method for the analysis of beer samples by atomic spectrometric techniques. The samples were prepared by acid decomposition using a reflux system, and the determinations carried out by F AAS (Fe, Mg and Zn), F AES (Na) and MIP OES (Ca, Fe, K, Mg, Mn, Na, Ni and Zn). The best conditions for sample decomposition were obtained by way of studies using a central rotational compound design: 10.0 mL of degassed beer followed by the addition of 5.0 mL of HNO3 and 2.0 mL H2O2 and a heating step in the digester block at 160 °C for 93 min. The quantification limits of the method were ≤ 0.100 mg L-1 for all the analytes investigated, regardless of the analytical technique used, values below those established by the Brazilian Health Surveillance Agency for Zn and Ni, for example. The comparative study of the different techniques showed that, according to the t-test at a 90% level of confidence, there was no significant difference for the determinations of Fe, Mg, Na and Zn in the beer samples. The sample preparation method was shown to be simple, fast, low-cost and reliable for the analysis of beers by the different atomic spectrometry techniques.

DETERMINAÇÃO DE METAIS POR TÉCNICAS DE ESPECTROMETRIA ATÔMICA EM AMOSTRAS DE CARVÃO MINERAL E CINZAS UTILIZANDO METODOLOGIA DE SUPERFÍCIE DE RESPOSTA

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.