Construção de uma cela de fluxo de longo caminho óptico para medidas espectrofotométricas

A simple and low-cost flow cell with 30 cm optical path for spectrophotometric measurements is described. It presents desirable characteristics such as low attenuation of the radiation beam and internal volume (75 µL) comparable to that of a 1-cm conventional cell (80 µL). Despite the increase in optical path, the effect on sample dispersion was also similar to that attained in the commercial cell. The performance of the cell was assessed by the determination of phosphate based on the molybdenum blue method, yielding a linear response range between 0.05 and 0.8 mg L-1 phosphorus (r=0.999). The increase in sensitivity (30.4-fold) in comparison with that obtained with a conventional 1-cm flow cell agreed with that estimated by the Lambert-Beer law.

Sensor Fusion of Proprioception, Force and Vision in Estimation and Robot

Sensor-based robot control allows manipulation in dynamic environments with uncertainties. Vision is a versatile low-cost sensory modality, but low sample rate, high sensor delay and uncertain measurements limit its usability, especially in strongly dynamic environments. Force is a complementary sensory modality allowing accurate measurements of local object shape when a tooltip is in contact with the object. In multimodal sensor fusion, several sensors measuring different modalities are combined to give a more accurate estimate of the environment. As force and vision are fundamentally different sensory modalities not sharing a common representation, combining the information from these sensors is not straightforward. In this thesis, methods for fusing proprioception, force and vision together are proposed. Making assumptions of object shape and modeling the uncertainties of the sensors, the measurements can be fused together in an extended Kalman filter. The fusion of force and visual measurements makes it possible to estimate the pose of a moving target with an end-effector mounted moving camera at high rate and accuracy. The proposed approach takes the latency of the vision system into account explicitly, to provide high sample rate estimates. The estimates also allow a smooth transition from vision-based motion control to force control. The velocity of the end-effector can be controlled by estimating the distance to the target by vision and determining the velocity profile giving rapid approach and minimal force overshoot. Experiments with a 5-degree-of-freedom parallel hydraulic manipulator and a 6-degree-of-freedom serial manipulator show that integration of several sensor modalities can increase the accuracy of the measurements significantly.

Desenvolvimento de um procedimento biamperométrico para determinação de sacarina em produtos dietéticos

In this work was developed a method for the determination of saccharin in dietary products by a biamperometric titration, using two silver electrodes as working electrodes and silver nitrate as titrant. It were used products as juices (light) and sweeteners with saccharin in concentrations ranged from 8.73 x 10-5 mol L-1 to 1.0 x 10-2 mol L-1, and the results were in close agreement with those data found using a HPLC method at a confidence level of 95%. The main advantages of the proposed method are its simplicity, rapid and low cost.

Determinação de metil-etil-cetona em amostras de urina com amostragem por micro extração em fase sólida (MEFS) em headspace associada à cromatografia gasosa com detector de ionização de chama (CG-DIC)

Methyl ethyl ketone (MEK) is a solvent commonly used in chemical, paint and shoe industry. The aim of this study was to develop and validate a method for urinary quantification of MEK, employing headspace solid phase micro extraction sampling (SPME) coupled to gas chromatography with flame ionization detection (GC-FID). The calibration curve (y=4.6851x-0.0011) presented good linearity with r²=0.9993. Accuracy (94-109%), intra-assay precision (4.07-5.91%) and inter-assay precision (3.03-5.62%) were acceptable. The quantification limit was 0.19 mg/L. This low cost method can be used routinely in the biological monitoring of occupational exposure to MEK, according to the requirements of the Brazilian legislation.

Construção de um sistema simples e compacto de recirculação d'água sob pressão para trompa d'água

Vacuum pumps are very useful in physical, chemical and biological experiments. In this communication it is described the design of a compact and low cost water recirculating system employing a water-jet aspirator pump as the vacuum source. The system requires only a water pump, water-jet aspirator pump, commercial PVC water tubes and a drain connection.

Validation of a simple and rapid UV spectrophotometric method for dexamethasone assay in tablets

This work reports the validation of an analytical UV spectrophotometric method to assay dexamethasone in tablets (assay and dissolution studies). The method was linear in the range between 1 and 30 µg mL-1 presenting a good correlation coefficient (r = 0.9998, n = 7). Precision and accuracy analysis showed low relative standard deviation (< 2.00%) and good percentual recoveries (95-105%). The procedure was linear, accurate, precise, and robust. The method is simple, and it has low cost. It does not use polluting reagents and can be applied in dissolution studies, being an adequate alternative to assay dexamethasone in tablets.

Cromatografia de afinidade por íons metálicos imobilizados (IMAC) de biomoléculas: aspectos fundamentais e aplicações tecnológicas

Immobilized Metal Ion Affinity Cromatography - IMAC - is a group-specific based adsorption applied to the purification and structure-function studies of proteins and nucleic acids. The adsorption is based on coordination between a metal ion chelated on the surface of a solid matrix and electron donor groups at the surface of the biomolecule. IMAC is a highly selective, low cost, and easily scaled-up technique being used in research and commercial operations. A separation process can be designed for a specific molecule by just selecting an appropriate metal ion, chelating agent, and operational conditions such as pH, ionic strength, and buffer type.

Extração e purificação de fármacos anti-inflamatórios não esteroidais ciclo-oxigenase-2 seletivos

Celecoxib (CB) and lumiracoxib (LM) are potent COX-2 inhibitors widely marketed for the treatment of rheumatoid arthritis and osteoarthritis. Nevertheless, it is difficult to obtain because it are protected under patents. The aim of this work was to develop an extraction method of drugs, CB and LM, in order to obtain the drug with a purity degree appropriated for use in research projects. The developed method showed to be effective of both drugs, becoming interesting due to its low cost, easy and speed of execution, application to different dosage forms (capsules and tablets) and drugs with different physicochemical properties.

Aplicação de espectroscopias raman e infravermelho na identificação e quantificação de plastificantes em filmes comerciais de PVC esticável

This paper reports the use of Raman and infrared techniques for the qualitative and quantitative analysis of plasticizers in polyvinylchloride (PVC) commercial films. FT-Raman marker bands were indentified for di-2-ethyl-hexyl adipate (DEHA) and di-2-ethyl-hexyl phthalate (DEHP), allowing for the rapid identification of these species in the commercial film. Quantitative analysis by FT-IR resulted in plasticizers concentrations ranging from 11 to 27% (w/w). Considering the little sample preparation and the low cost of the techniques, FT-IR and FT-Raman are viable techniques for a first assessment of plasticizers in commercial samples.

Remoção de metais de solução aquosa usando bagaço de caju

The metal ions removal on cashew bagasse, a low-cost material, has been studied by batch adsorption. The parameters chemical treatment, particle size, biosorbent concentration, and initial pH were studied. In this study the maximum ions removal was obtained on the cashew bagasse treated with 0.1 mol/L NaOH/3 h, at optimum particle size (20-59 mesh), biosorbent concentration (50 g/L) and initial solution pH 5. The kinetic study indicated that the adsorption metal follows pseudo-second order model for a multielementary system and equilibrium time was achieved in 60 min for all metal ions.

Determinação condutométrica de cloridrato de metformina em formulações farmacêuticas empregando nitrato de prata como titulante

A simple, precise, rapid and low-cost conductometric titration method for the determination of metformin hydrochloride (MET) in pharmaceuticals using silver nitrate as titrant is proposed. The method was based on the chemical reaction between the chloride of metformin hydrochloride molecule and Ag(I) ions, yielding the precipitate AgCl(s). The method was applied for MET determination in three pharmaceuticals and the obtained results with proposed method were in close agreement with those results obtained using an official method of the British Pharmacopoeia, at a 95% confidence level.

Construção e caracterização de um detector eletroquímico para análises em fluxo

The present work describes a low-cost electrochemical "wall-jet" detector for flow analysis. The electrolytic solution enters into the cell through a tube of stainless steel (200 to 300 µm i.d), reaching to the center of the working electrode perpendicularly and then being mixed to the remaining solution in the cell, which flows under atmospheric pressure into a waste reservoir. The proposed electrochemical detector can be used with any type of working electrode, from commercial to home-made, such as glassy carbon and metallic electrodes (modified or unmodified), which enlarge the applications of the electrochemical detector.

Determinação espectrofotométrica de hexametilenotetramina (HMT) em medicamentos, utilizando ácido cromotrópico e forno de micro-ondas

This paper proposes a methodology for spectrophotometric determination of hexamethylenetetramine (HMT) by using chromotropic acid in a phosphoric acid media employing a domestic microwave oven as a source of heating. The reddish-purple soluble product is quantitatively formed after 30 s of irradiation and obeys the Beer´s law in the range between 0.1-1.2 mg L-1 HMT (r = 0.99925). The method was applied successfully in commercial pharmaceutical preparations containing dyes in their composition. The results showed that the method proposed is feasible for simplicity, speed, low cost, precision and accuracy when compared with United States Pharmacopeia official method.

Desenvolvimento e aplicação de sistema passivo de coleta de poluentes atmosféricos para monitoramento de Cd, Cr, Pb, Cu, Fe, Mn, Zn e particulados totais

The objective of this study was to assess a new monitoring technique of particulate and trace metals in the atmosphere via the use of a passive sampler of air pollutants in the city of Goiânia. The average particulate weight and average concentrations of metals Fe, Cr, Zn, Pb, Cu, Mn, and Cd were 0.1104 g and 257.5; 23.4; 17.8; 6.7; 1.9; 0.8; 0.2 μg/m²/day, respectively. Higher Pb and Cr concentrations were obtained in areas with intense traffic. This study revealed that it is possible to monitor trace metals with passive sampling, developed at a low cost and operational facility.

Em busca da sustentabilidade: células solares sensibilizadas por extratos naturais

The present work reports the use of anthocyanins extracted from mulberry (Morus Alba L.), raspberry (Rubus Idaeus L.) and blueberry (Vaccinium myrtillus L.) as sensitizers in dye-sensitized solar cells. The conversion efficiency of these devices is dependent on the extracts employed and can be rationalized in terms of their composition and spectral properties. Solar cells sensitized by the mulberry extract showed the highest efficiency among the fruits investigated. Moreover, a 16 cm² active area solar cell with the mulberry extract has presented fair good efficiency of conversion for natural dye-based solar cells, besides stability over twenty weeks, showing perspectives for developing these low cost devices with a commercial viability.