Anderson A. Rocha

Extraction induced by emulsion breaking for metals determination in diesel oil by ICP-MS

This present work proposes a new approach for diesel oil preparation for metals determination by ICP-MS. The proposed methodology is based on the extraction of the elements of interest into an aqueous phase employing the extraction induced by emulsion breaking procedure. In this approach, the diesel oil was emulsified with an acid surfactant (Triton X-114) solution in order to form a stable water-in-oil emulsion. Further, the emulsion was broken by centrifugation for 60 min at 3200 rpm, yielding two separated phases: (i) the upper organic phase, containing the diesel oil mixed with the surfactant and (ii) the lower acidic aqueous phase, containing the elements of interest that were extracted from oil. Then, the lower phase was collected, diluted and the analytes were determined by ICP-MS using the internal standardization method. The optimization of the methodology was carried out by analyzing the effect of several parameters that could affect the extraction efficiency such as the concentrations of HNO3 and Triton X-114 in the solution used for emulsification (and extraction), the extraction and collection times and the calibration strategy. The limits of detection and quantification for the elements of interest (Al, Cu, Mn, Ni, Sn and V) were in the range of 26–88 ng L−1 and 86–295 ng L−1, respectively. The accuracy of the methodology was tested by the analysis of spiked samples, since there are no certified samples of diesel oil available in the market. The recovery percentages were in the range of 84–113%. The developed methodology was successfully applied in the metals determination in five commercial diesel oils of different brands.

Determination of inorganic mercury in petroleum production water by inductively coupled plasma optical emission spectrometry following photochemical vapor generation

A photochemical vapor generation system coupled to an inductively coupled plasma optical emission spectrometer (ICP-OES) was used for the determination of inorganic mercury in high salinity water arising from offshore petroleum exploration platforms, i.e., production water (PW). The system comprised a 17 W UV grid lamp for photogeneration along with two gas/liquid separators functioning in tandem to minimize aerosol transport into the plasma. Analytical conditions, including the type and concentration of low molecular weight organic acid, UV exposure time and solution pH, were optimized. Continuous-flow processing of a sample containing 1.63 mol L−1 formic acid at pH 1.5 for a UV irradiation time of 30 s permitted Hg(II) to be determined based on the method of addition. Procedural limits of detection and quantification of 1.2 and 4.0 μg L−1, respectively, were achieved. In the absence of a suitable certified reference material with which the methodology has to be validated, recoveries of 10–40 μg L−1 Hg(II) spikes added to real samples were examined and ranged from 79 to 121%.

Synthesis and evaluation of D-gluconamides as green mineral scales.

A series of 13 D-gluconamides were synthesized in moderate to good yields and evaluated as green scale inhibitors. The crystal structures of two compounds were determined by X-ray crystallography. The compounds 6c and 6d showed a reasonable inhibition of BaSO(4) precipitation from aqueous solution (47% and 51%, respectively) that indicated the potential for these derivatives of δ-gluconolactone.

CF-LIBS analysis of frozen aqueous solution samples by using a standard internal reference and correcting the self-absorption effect

The aim of this paper is to present an innovative procedure to determine the composition of a liquid sample using Laser Induced Breakdown Spectroscopy without calibration curves, or the so-called CF-LIBS (Calibration Free-Laser Induced Breakdown Spectroscopy). Our results of CF-LIBS for the elemental composition were compared with the sample standard concentration determined by Microwave Plasma-Atomic Emission Spectroscopy (MP-AES). In this work, a controlled amount of an internal standard, an extra chemical element, is placed into a liquid sample that is afterward frozen to produce a solid target. The plasma of the target material is produced at atmospheric pressure by focusing a Nd:YAG laser on the frozen target surface. Time-resolved emission spectra are acquired and used for quantitative analysis. An extraordinary increase in the accuracy of elemental concentration is achieved when the spectroscopic data are corrected through an analytical elimination of the self-absorption effect. The corrected data plotted in a Boltzmann diagram show that CF-LIBS can provide good analytical sensitivity and accurate and reliable elemental concentrations when the local thermodynamic equilibrium conditions are experimentally fulfilled and the self-absorption effect on the line intensities is corrected. In the case analyzed here, the concentration results obtained by the improved CF-LIBS procedure give relative deviations of 3.3% maximum when compared with those of MP-AES.

Effect of dentifrice containing fTCP, CPP-ACP and fluoride in the prevention of enamel demineralization

Abstract Objective: To evaluate the effect of different fluoride- and calcium- and/or phosphate-containing products on their ability to prevent enamel demineralization under pH cycling conditions. Material and methods: Enamel bovine specimens were assigned to the following groups: G1-MPP (MI Paste Plus, 0.2% NaF, Recaldent™, GC Corporation Tokyo, Japan); G2-FD (Crest™ Cavity Protection, 0.243% NaF, Procter & Gamble, USA); G3-CLP (Clinpro™ 5000, 1.1% NaF, 3M ESPE, USA); and G4-CO (Control without fluoride, Silica-based dentifrice; Daudt Ltda, Brazil). The specimens were soaked in demineralizing solution for 6 h and remineralizing solution for 18 h alternatively for 10 days. The toothpaste was prepared with deionized water in a 1:3 ratio (w/v) for three minutes daily. The solutions were renewed every 48 h. After cycling, enamel changes were analysed by percentage change of SMH (%SMH) and energy-dispersive X-ray spectroscopy (EDS). The %SMH value observed for G3-CLP (2.9 ± 39.2) was higher than that found in G4-CO (−13.0 ± 20.7), G1-MPP (−8.9 ± 20.9) and G2-FD (−3.9 ± 27.1). The %SMH was similar for all treatment groups (one-way ANOVA and Tukey’s HSD; p < .05). The pH, Ca2+ and Ptotal in the remineralization solutions were not different among all groups (Kruskal–Wallis; p < .05). At 24 h, the Ca2+ concentration in the demineralization solution was significantly lower in G1-MPP. Ca2+ concentration increased in all groups after 48 h, except for G3-CLP. The EDX quantitative analysis showed that the atomic % of elements is lower level at G4-CO. Conclusions: The Clinpro™ 5000 demonstrated having the most protective effect against demineralization; however, the % SMH was similar for all groups.

Recuperação Avançada de Petróleo: Potencialidades da Injeção WAG (Water Alternating Gas)

The increase in the recovery factor in an oil reservoir is an essential goal in the oil industry and in this sense, complementary and alternative methodologies have been developed, for example, the alternating injection of water and gas (WAG), which has been used ever as a more advanced method of recovering oil. This method combines the best gas displacement and swept the water efficiencies. Recent discoveries of oil reserves in the Pre-Salt layer, with a significant amount of gas whose CO 2 content is in the range 8-12%, the use of CO 2 gas in WAG injection (WAG-CO 2 ) has emerged as an opportunity for Brazil. Besides the good prospect of increased oil recovery factor of these reservoirs, this process is in line with mitigation actions by greenhouse emissions CO 2 . This article is a compilation of WAG application projects in the literature, as well as issue related to Brazilian initiatives that focuses on numerical simulations using reservoir models, since the carbonate rocks common to the pre-salt reservoirs are reactive the injected fluids . DOI: 10.5935/1984-6835.20160055

Mineral scale deposition in surfaces: Problems and opportunities in the oil industry

The deposition or mineral scaling on surfaces is caused by the accumulation of inorganic salts. When it occurs in oil and gas production equipment, it causes major operational problems and severe damage to the pipes. Besides oil wells at sea, this phenomenon also occurs on the surface of membranes used in filtration, treatment and sulphate removal of sea water. Its origins lie in the incompatibility between the chemical composition of the formation and injection water or in the thermodynamic changes of system. These of the disadvantage can be prevented by the use of chemicals that act as scale inhibitors. This article discusses the origin of scale and its implications, and addresses the chemical classes, natural and synthetic, which are used as anti-fouling, as well as promising substances for this purpose.