Biochemical analysis and clinical tests like glucose, hemoglobin, cholesterol, iron, etc. are crucial for early illness diagnosis like diabetes, anemia and coronary deceases. These tests usually are done in state of the art instruments in well equipped laboratories in health centers. In some cases, these instruments are not portable, so they are not recommended for clinical field studies in remote areas. The present work shows a portable low-cost prototype of multi-well plates reader designed for clinical analysis. A Light Emission Diodes (LEDs) array is used as excitation source and an inexpensive webcam as detector. The light source illuminates the 96 well plates and the webcam take the image with 640x480 pixels. The data is acquired and processed by using a portable computer. 96 samples can be read including blanks and calibration standards simultaneously. Light absorption data are processed using a MatLab software designed in our laboratory to obtain calibration curves, standards lectures and samples concentration. The system was evaluated using different analytes series solutions: Neutral Red, Cooper (II) Ammonia Complex and Methyl Orange. The results shows that it is possible to measure few micro liters of solutions with adequate exactitude and precision of less than 3%. As possible analytical clinical application, iron determination was performed using Fe(III) Thiocyanate complex. This method is usually applied in serum samples analysis. The sensibility achieved with the proposed instrumentation configurations allows the analysis of iron in serum samples in the references values normal range (0.75 - 1.5 mg/L) in human.
The asphaltenes flocculation process in heavy crude oils is a subject of great interest for the oil industry due to the negative effect of this process in the oil extraction. In this work we present the application of the Confocal Microscopy to the study of the aggregation process of asphaltene in crude oils. The advantages of the technique for study of the particles in surface and in the dispersed phase are shown. Confocal images of different shows changes in the behavior of the differents solutions. The results can be related with the stability and the prediction of asphaltene precipitation in crude oils.
Fluorescence spectroscopy provides a powerful method in studies investigates complex molecules. In this work we present some fluorescence studies about molecular aggregation of asphaltenes in toluene and tethahidrofuran (thf) solution were carried out. The fluorescence was induced by a CW Ar+ laser (λexc = 514.5 nm). At low concentration (< 500 mgL-1) no red shift was observed in fluorescence spectra, but the dependence of the fluorescence intensity with the solution concentration have a linear increase below 50 mgL-1, then, for higher samples concentration a dramatical dismished as the concentration increased is observed, which can attributed to the asphaltene aggregation.
Molecular absorption and fluorescence studies of Asphaltenes in toluene solution and thin films absorbed onto glass plates were carried out. The fluorescence was induced by two different type of laser: a CW Ar+ and Nd-Yag laser. A red shifted was observed in both: fluorescence and absorption spectra, which can be attributed to asphaltenes aggregation. Experiments made with sample films in glass plate with the 532 nm Nd-Yag laser, shows a very narrow band at 566.1 nm (1126 cm-1) but with higher relative intensity compare to those obtained with CW laser, which is attributed to a Raman line. This signal can be employed to perform adsorption studies onto solid surfaces.
In this work we present an application of the forward-angle light scattering (FAST) for the flocculation point determination in asphaltene-toluene solutions. This technique allows to obtain an accurate and precise flocculation point determination compare to those obtained by traditional techniques. Estimations of flock dimensions based in the FAST measurements are presented.
In the present work an application of z-scan technique to the study of asphaltenes is presented in order to determine their nonlinear properties. For asphaltenes toluene solution a high value of nonlinear refraction index (n2 equals 6.04 X 10-12) it is obtained. Strong dependence of the two photon absorption coefficient ((beta) ) with the input intensity was observed for higher solutions concentration, which can be explained by molecular aggregation.
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