Rafael Arromba de Sousa

Automatic microemulsion preparation for metals determination in fuel samples using a flow-batch analyzer and graphite furnace atomic absorption spectrometry.

The principal thermodynamic advantages of using microemulsions over standard emulsions for flow metal analysis are the greatly increased analyte stability and emulsive homogeneity that improve both the ease of sample preparation, and the analytical result. In this study a piston propelled flow-batch analyzer (PFBA) for the determination of Cu, Cr and Pb in gasoline and naphtha by graphite furnace atomic absorption spectrometry (GF AAS) was explored. Investigative phase modeling for low dilution was conducted both for gasoline and naphtha microemulsions. Rheological considerations were also explored including a mathematical flow derivation to fine tune the systems operational parameters, and the GF AAS coupling. Both manual and automated procedures for microemulsion preparation were compared. The results of the paired t test at a 95% confidence level showed no significant differences between them. Further recovery test results confirmed a negligible matrix effect of the sample on the analyte absorption signals and an efficient stabilization of the samples (with metals) submitted to microemulsion treatment. The accuracy of the developed procedure was attested by good recovery percentages in the ranges of 100.0±3.5% for Pb in the naphtha samples, and 100.2±3.4% and 100.7±4.6% for Cu and Cr, respectively in gasoline samples.

Determination of metals in Brazilian coconut water using an inductively coupled plasma optical emission spectrometer

The metal content of coconut water was investigated in samples from different Brazilian states. Ca, Mg, Mn, Fe, Zn and Cu were determined without a mineralization step using the ICP OES technique. Employing optimized instrumental parameters, RSD usually lower than 2% and good accuracy were obtained. LOD values (mg L-1) were: Ca 0.06, Mg 0.004, Mn 0.02, Fe 0.16, Zn 0.008 and Cu 0.006. The concentration ranges (mg L-1) of the analytes in the samples studied were: Ca (107 - 237), Mg (50 - 88), Mn (1 - 5) and Zn (0.04 - 0.18). Considering the Reference Daily Intakes for Minerals (RDI) it was estimated that the nutritional contribution from the ingestion of 400 mL of the beverage corresponds to approximately 7% of the RDI for Ca and Mg and 58% for Mn.

Classificação de água de coco processada e natural por meio de HCA, PCA e teores de íons metálicos determinados por ICP OES

Inductively Coupled Plasma Optical Emission Spectrometry was used to determine Ca, Mg, Mn, Fe, Zn and Cu in samples of processed and natural coconut water. The sample preparation consisted in a filtration step followed by a dilution. The analysis was made employing optimized instrumental parameters and the results were evaluated using methods of Pattern Recognition. The data showed common concentration values for the analytes present in processed and natural samples. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) indicated that the samples of different kinds were statistically different when the concentrations of all the analytes were considered simultaneously.

Analysis of liquid stevioside and cyclamate-saccharin dietetic sweeteners by inductively coupled plasma optical emission spectrometry without sample treatment

An analytical method for the determination of inorganic species in liquid cyclamate-saccharin and stevioside sweeteners is presented. The method is based on inductively coupled plasma optical emission spectrometry and allowed analysis without prior sample treatment. Instrumental parameters were optimized according to plasma robustness and the signal to background ratio. The accuracy of the method was evaluated for As, Ca, Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb, and Zn employing analyte addition and recovery experiments. The recovery values were between 90 and 110% for the majority of the analytes, the RSDs obtained were, in general, lower than 5% and the limits of detection were in the range 0.7 (Mg) - 71 (Pb) µg L-1. The analyses of different samples indicated that the average values of many of the analytes studied were different for the two types of samples. Copper and Zn concentrations were in the same range and As, Co, and Pb were not detected in any samples.

Aproveitamento sustentável de biomassa e de recursos naturais na inovação química

Increased production of biomass is currently the only immediately accessible alternative for large-scale carbon sequestration and it can produce large amounts of food, fuel and raw materials for the chemical industry that can in turn growingly replace oil as a source of organic building blocks and also of hydrogen and sulfur. Development of processes for biomass and abundant minerals transformation into chemical raw materials should now benefit from large inputs from nanotechnologies, biotechnologies, information and micro-reactor technologies. Success in R&D&Innovation along this line can yield new products and processes needed to perform desirable functions within a sustainable development paradigm.

Tratamento dos resíduos gerados na síntese de polianilina em escala pré-piloto

Polyaniline (PAni) is one of the most studied conducting polymer. It can be synthesized by two methods: electrochemical or chemical oxidation. The chemical oxidation is more adequate to produce large quantities of polymer. Regardless of the synthesis scale, the treatment of the residues before its final destination is very important and necessary because it contains toxic aniline derivatives (carcinogens in some cases), acids and inorganic salts, both with low toxicity. In this work we discuss the methods used to treat these residues and to eliminate and discard the toxic substances. These were extracted from the reaction residues by using activated coal and the pH of the residue was neutralized.