MÉTODO DE SÍNTESE DE AZIDAS AROMÁTICAS USANDO VINAGRE

The present paper describes a simple and low-cost procedure for preparation of aryl azides from anilines using vinegar as an unusual solvent/reagent. We observed the sequence of diazotation followed by diazo displacement with sodium azide can be carried out in aqueous solution of acetic acid

NOVO SORVENTE DE HIDROFOBICIDADE REDUZIDA PARA EXTRAÇÃO EM FASE SÓLIDA: PREPARAÇÃO E CARACTERIZAÇÃO

C18 chemically bonded sorbents have been the main materials used in solid phase extraction (SPE). However, due their high hydrophobicity some hydrophobic solutes are strongly retained leading to the consumption of larger quantities of organic solvent for efficient recoveries. This work presents a sorbent with lower hydrophobicity but similar selectivity to the C18 sorbent, prepared by thermal immobilization of poly(dimethylsiloxane-co-alkylmethylsiloxane) (PDAS) on silica. PDAS has organic chains with methyl groups alternating with octadecyl or hexadecyl groups in its monomeric unities. For the Si(PDAS) sorbent presented, the polymeric layer was physically adsorbed on the silica surface with 12% carbon load. Although the coating of silica with the polymeric layer was incomplete, the PDAS provided better protection for the silica surface groups, promoting mostly hydrophobic interactions between analytes and the sorbent. Sorption isotherm studies revealed that the retention of hydrophobic solutes on Si(PDAS) was less intense than on conventional sorbents, confirming the lower hydrophobicity of the lab-made sorbent. Additional advantages of Si(PDAS) include simplicity and low cost of preparation, making this material a potential sorbent for the analysis of highly hydrophobic solutes.

VALIDAÇÃO INTRALABORATORIAL DA DETERMINAÇÃO DE METILTESTOSTERONA EM ÁGUAS NATURAIS POR VOLTAMETRIA USANDO ELETRODO DE GOTA PENDENTE DE MERCÚRIO

17α-methyltestosterone (17α-MT) is a hormone used in medicine and aquaculture which can be found in natural waters. It is considered an emerging organic pollutant and its accurate and precise analysis is required. Therefore, this study presents the in-house validation of a new voltammetric methodology for 17α-MT analysis in natural waters. A hanging mercury drop electrode and NaOH 5.0×10-3 mol L-1 solution as the electrolyte were employed in the voltammetric determinations. To confirm the presence of 17α-MT in water samples quantitative analysis was performed by ESI-MS/MS. The methodology exhibited good selectivity, linearity, accuracy (recovery of between 100.4 and 108.8%) and precision (RSDs for repeatability of 2.85% and for intermediate precision of 14.10%, with n = 5, respectively). LOD and LOQ were 3.07 µg L-1 and 10.78 µg L-1, respectively. The methodology was suitable for determination of 17α-MT in natural waters due to low-cost, good performance and no sample pre-treatment required.

EXTRAÇÃO ASSISTIDA POR ULTRASSOM PARA DETERMINAÇÃO COLORIMÉTRICA DE FERRO EM SOLO: UMA COMPARAÇÃO COM ESPECTROMETRIA DE MASSA COM PLASMA INDUTIVAMENTE ACOPLADO

A simple procedure for ultrasound-assisted extraction and colorimetric determination of iron in soil samples was developed. The iron concentration in the analyzed samples was determined by the colorimetric method and the results compared with inductively coupled plasma mass spectrometry (ICP-MS). Fifteen soil samples were analyzed and the iron concentration results compared with those obtained by ICP-MS using microwave-assisted sample digestion. The proposed procedure showed good efficiency for iron extraction and the results obtained by colorimetric determination exhibited good agreement with ICP-MS. Moreover, ultrasound-assisted extraction and colorimetric determination is a simple, fast and low-cost procedure for application in routine analysis.

RECENTES APLICAÇÕES EM SÍNTESE ORGÂNICA DE CATÁLISE FOTO REDOX MEDIADA POR LUZ VISÍVEL

In the past few years, photoredox catalysis has become a powerful tool in the field of organic synthesis. Using this efficient method, it is possible to excite organic compounds from visible light and attain alternative mechanistic pathways for the formation of chemical bonds, a result which is not obtainable by classical methods. The rapid growth of work in the area of photoredox catalysis is due to its low cost, broad chemical utility protocols, and, especially, its relevancy from the green and sustainable chemistry viewpoints. Thus, this study proposes a brief theoretical discussion of and highlights recent advances in visible-light-induced photoredox catalysis through the analysis of catalytic cycles and intermediates.

DESENVOLVIMENTO DE UMA TÉCNICA ULTRASSÔNICA PARA AVALIAR TEORES DE ÓLEO E GRAXA EM EFLUENTES DE BIOCOMBUSTÍVEIS

Ultrasound as a metrology tool has many applications in health care, industrial, and chemical analyses. Ultrasonic techniques are rapid, low-cost, non-invasive, and highly repeatable. Although ultrasound can be used to measure emulsions, no effort had been made thus far to optimize its sensitivity for metrological analysis. In this work, a technique for analyzing oil in water was validated. The wave velocity and attenuation were chosen as the ultrasonic parameters. The technique was implemented in the boundary region established by law for effluents from industrial plants involved with biofuel manufacturing. A technical effort of this study was to establish stable emulsions in concentrations close to the desired limit of study. The phase behaviours of pseudo-ternary oil, sodium chloride, and sodium lauryl sulphate were studied. The composition in the widest region of the diagram allowed for the formation of a stable emulsion, from which the ultrasound measurement was carried out. An analytical curve was obtained using ultrasonic attenuation to determine the content of oils and greases in wastewater ranging 15–240 ppm. The speed of sound did not appear to be an applicable parameter for this application. The technique was demonstrated to be an important alternative solution for the continuous monitoring of wastewater with regard to oil concentrations.

PREPARAÇÃO DE PONTOS DE CARBONO E SUA CARACTERIZAÇÃO ÓPTICA: UM EXPERIMENTO PARA INTRODUZIR NANOCIÊNCIA NA GRADUAÇÃO

Carbon dots (CDs) constitute a new class of carbon-based nanomaterials that measure less than 10 nm and display attractive physical and chemical features such as fluorescence. CDs have been considered the new “power” carbon nanomaterials since their accidental discovery in 2004. This study reports a simple, easy, and accessible experiment for undergraduate courses. The experiment involves the preparation of CDs by pyrolysis using commercial gelatin as a low cost precursor as well as CD purification and optical characterization. The optical properties of CDs such as absorption and emission properties make them a promising material for teaching the basic concepts and techniques used for characterization of nanomaterials. Also, the reactants and final product are suitable for undergraduate courses since they are non-toxic materials. The prepared CDs can be used in such applications as bioimaging, solar cells, and photocatalysis.

DEVELOPMENT AND VALIDATION OF ANALYTICAL METHOD FOR PALM OIL DETERMINATION IN MICROCAPSULES PRODUCED BY COMPLEX COACERVATION

The microencapsulation of palm oil may be a mechanism for protecting and promoting the controlled release of its bioactive compounds. To optimize the microencapsulation process, it is necessary to accurately quantify the palm oil present both external and internal to the microcapsules. In this study, we developed and validated a spectrophotometric method to determine the microencapsulation efficiency of palm oil by complex coacervation. We used gelatin and gum arabic (1:1) as wall material in a 5% concentration (w/v) and palm oil in the same concentration. The coacervates were obtained at pH 4.0 ± 0.01, decanted for 24 h, frozen (−40 ºC), and lyophilized for 72 h. Morphological analyzes were then performed. We standardized the extraction of the external palm oil through five successive washes with an organic solvent. We then explored the best method for rupturing the microcapsules. After successive extractions with hexane, we determined the amount of palm oil contained in the microcapsules using a spectrophotometer. The proposed method was shown to be of low cost, fast, and easy to implement. In addition, in the validation step, we confirmed the method to be safe and reliable, as it proved to be specific, accurate, precise, and robust.

DESENVOLVIMENTO DE EXPERIMENTO DIDÁTICO DE ELETROGRAVIMETRIA DE BAIXO CUSTO UTILIZANDO PRINCÍPIOS DA QUÍMICA VERDE

In this paper, we describe the development of low-cost teaching experiments of electrogravimetry for undergraduate students using principles of green chemistry. Copper was electrochemically deposited on brass under an electrical current density of 50 mA cm−2 from acidic solutions containing nitrate anions. Color changes at the brass electrode and of the solution were observed, indicating that the reduction of copper ions had occurred. The deposition efficiency values were between 92.8% and 93.8%, and the electrochemical efficiency values were between 85.6% and 86.5%. There was no significant contribution from parallel reactions. These experimental conditions facilitated the didactic exploration of gravimetric and electrochemical concepts. Following the principles of green chemistry, the experiments produced no toxic substances, all the materials could be recycled, and the energy consumption was the lowest. For this reason, this experiment was considered to be very interesting for didactical purposes.

Trolley R&D project for a small portal log yard crane

This master’s thesis was done for Andritz Inc. Atlanta Georgia. The purpose of the thesis was to develop a new trolley for a small portal log yard crane. In the beginning of the thesis the basic principles of the systematic design processes have been described, along which the design work of the trolley has proceeded. The second literature part consists of the design and dimensioning of the welded steel structures under fatigue loading. The design work of the trolley consists of the engineering and the selection of the mechanical components and the design of the load carrying structure for the trolley. The realization of the steel structure of the trolley is based on the fatigue and static dimensioning. The fatigue dimensioning is grounded in the life expectations estimated for the trolley and the static dimensioning is based on the CMAA guidelines. The computer aided element method was utilized in the design of the steel structure. The effective notch method and the hot spot method were used in the fatigue calculations. The trolley structure was carried out by using the sheet metal parts in order to manufacture the structure as effective and low cost way as possible. The corner stone of the dimensioning of the trolley structure was the utilization of the open profiles made of welded or cold formed sheet metals, which provide better weldability, weld inspection, access for repairs and corrosion protection. As a last part of the thesis a new trolley traveling system was developed. The distribution of the wheel loads of the trolley bogies on the main girder was also studied, which led to an innovative suspension arrangement between the trolley leg and the bogie. The new bogie solution increases the service life of the main girder of the crane and improves the stability of the bogies. The outcome of the thesis is an excellent trolley structure from the weight and the service life point of view.

Uses of natural zeolite in the removal of Pb2+ from contaminated water

In this paper, we carry out a study on the process of sorption of lead in polluted waters usingnatural zeolites, with the objective of analyzing their behavior in the purification of water.Experiments are carried out under static and dynamic conditions to determine the influence of other metal ions, such as: Ca (II), Mg (II), K (I) and Na (I), on this process. We demonstrate that the affinity of Pb (II) with regard to zeolite is higher than that of the ions mentioned above. It allows us to use this material in the capture of lead in residual waters. A lineal model of regression was obtained using a computer program called Eureka which relates the capacity of interchange of zeolite with respect to the concentration of the metal ions present in waters. We also studied the selectivity of zeolite in the process of sorption of Pb (II) compared with other heavy metals like Zn (II) and Cd (II).The results achieved in both cases increase the expectancy about the usage of zeolite as a low cost material for purifing waters.

Quality and analysis of administration processes in server operations

IT outsourcing refers to the way companies focus on their core competencies and buy the supporting functions from other companies specialized in that area. Service is the total outcome of numerous of activities by employees and other resources to provide solutions to customers' problems. Outsourcing and service business have their unique characteristics. Service Level Agreements quantify the minimum acceptable service to the user. The service quality has to be objectively quantified so that its achievement or non-achievement of it can be monitored. Usually offshoring refers to the transferring of tasks to low-cost nations. Offshoring presents a lot of challenges that require special attention and they need to be assessed thoroughly. IT Infrastructure management refers to installation and basic usability assistance of operating systems, network and server tools and utilities. ITIL defines the industry best practices for organizing IT processes. This thesis did an analysis of server operations service and the customers’ perception of the quality of daily operations. The agreed workflows and processes should be followed better. Service providers’ processes are thoroughly defined but both the customer and the service provider might disobey them. Service provider should review the workflows regarding customer functions. Customer facing functions require persistent skill development, as they communicate the quality to the customer. Service provider needs to provide better organized communication and knowledge exchange methods between the specialists in different geographical locations.

Potentiometric determination of captopril in pharmaceutical formulations

A simple, precise, rapid and low-cost potentiometric method for captopril determination in pure form and in pharmaceutical preparations is proposed. Captopril present in tablets containing known quantity of drug was potentiometrically titrated in aqueous solution with NaOH using a glass pH electrode, coupled to an autotitrator. No interferences were observed in the presence of common components of the tablets as lactose, microcrystalline cellulose, croscarmellose sodium, starch and magnesium stearate. The analytical results obtained by applying the proposed method compared very favorably with those obtained by the United States Pharmacopoeia Standard procedure. Recovery of captopril from various tablet dosage formulations range from 98.0 to 102.0%.

Spectrophotometric determination of diclofenac in pharmaceutical preparations assisted by microwave oven

In this work, an effective and low-cost method for the determination of sodium or potassium diclofenac is proposed in its pure form and in their pharmaceutical preparations. The method is based on the reaction between diclofenac and tetrachloro-p-benzoquinone (p-chloranil), in methanol medium. This reaction was accelerated by irradiating of reactional mixture with microwave energy (1100 W) during 27 seconds, producing a charge transfer complex with a maximum absorption at 535 nm. The optimal reaction conditions values such as reagent concentration, heating time and stability of the reaction product were determined. Beer's law is obeyed in a concentration range from of 1.25x10-4 to 2.00x10-3 mol l-1 with a correlation coefficient of 0.9993 and molar absorptivity of 0.49 x10³ l mol-1 cm-1. The limit of detection (LOD) was 1.35x10-5 mol l-1 and the limit of quantification (LOQ) was 4.49x10-5 mol l-1. In the presence of the common excipients, such as glucose, lactose, talc, starch, magnesium stearate, sodium sulphite, titanium dioxide, polyethyleneglycol, polyvinylpirrolidone, mannitol and benzilic alcohol no interferences were observed. The analytical results obtained by applying the proposed method compare very favorably with those given by the United States Pharmacopeia standard procedure. Recoveries of diclofenac from various pharmaceutical preparations were within 95.9% to 103.3%, with standard deviations ranging from 0.2% to 1.8%.