Trace level vanadium determination is reported using a dual beam thermal lens spectrometer. The t... more Trace level vanadium determination is reported using a dual beam thermal lens spectrometer. The thermal lens was generated using an argon ion beam laser (pump beam) which was focused into a sample cuvette. The thermal lens signal (TLs) was monitored with a He-Ne laser beam and a photodiode detector. Multichannel averager software was developed for processing the transient TLs. The optimal set up, ensuring maximum sensitivity and linear calibration graphs was obtained using experimental design techniques. Under optimized conditions, the detection limits for aqueous and ethanol-water (2+3 v/v) and (4+1 v/v) vanadium complex solutions were, respectively, 0.0071 mg/l, 0.0065 and 0.0039 mg/l.
Nanoparticles with optical and magnetic responses are of great applicability in different fields.... more Nanoparticles with optical and magnetic responses are of great applicability in different fields. In this work, zero valent iron nanoparticles were prepared by laser ablation and stabilized in a surfactant solution to keep particles dispersed and protected in the solution. Optical and magnetic properties of nanoparticles were measured, by UV and Mössbauer spectroscopy. The results show the formation of nanoparticles of a-Fe (ferromagnetic). Our method of preparation, which uses a high H + concentration in the medium, diminishes the zero valent iron oxidation, producing iron nanoparticle with a core of a-Fe and a small shell probably composed of iron oxides.
Nanoparticles with optical and magnetic responses are of great applicability in different fields.... more Nanoparticles with optical and magnetic responses are of great applicability in different fields. In this work, zero valent iron nanoparticles were prepared by laser ablation and stabilized in a surfactant solution to keep particles dispersed and protected in the solution. Optical and magnetic properties of nanoparticles were measured, by UV and Mössbauer spectroscopy. The results show the formation of nanoparticles of α-Fe (ferromagnetic). Our method of preparation, which uses a high H + concentration in the medium, diminishes the zero valent iron oxidation, producing iron nanoparticle with a core of α-Fe and a small shell probably composed of iron oxides.
The present work studied the effects of crude oil solution concentration, reservoir temperature, ... more The present work studied the effects of crude oil solution concentration, reservoir temperature, and n-heptane addition flow rate on asphaltenes flocculation onset by using an automatic titration system. These effects were evaluated through the application of a central composite design that allows the simultaneous evaluations of the experimental parameters under study. Results showed that the onset measurements were strongly affected by the crude oil solution concentration, mainly on unstable crude oil samples. This phenomenon can be used to estimate the crude oil stability. On the other hand, temperature of the sample reservoir and precipitant addition showed a slight effect on the flocculation onset.
This work presents a new surface plasmon resonance (SPR) instrument based on Kretschmann configur... more This work presents a new surface plasmon resonance (SPR) instrument based on Kretschmann configuration. This device acquires and processes the reflected SPR image of the sample by using a webcam together with an image processing algorithm that transforms the RGB image in numeric values and correlates the integrated intensity with the refractive index of the solution. Experimental signals were compared with theoretical values and it was found an excellent agreement. In addition, the applicability of the instrument was tested by measuring the refractive index of solutions in a continuous flow mode. Excellent stability and sensitivity of the signal were found in the presence of small changes of the refractive index.
Biochemical analysis and clinical tests like glucose, hemoglobin, cholesterol, iron, etc. are cru... more 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.
In this work, we measure the refractive index of crude oils and asphaltene in toluene solutions u... more In this work, we measure the refractive index of crude oils and asphaltene in toluene solutions using a fiber optic refractometer designed to work with high-viscosity and high optical density samples. The data of the samples were analyzed using the Lorentz−Lorenz theory and ...
Trace level vanadium determination is reported using a dual beam thermal lens spectrometer. The t... more Trace level vanadium determination is reported using a dual beam thermal lens spectrometer. The thermal lens was generated using an argon ion beam laser (pump beam) which was focused into a sample cuvette. The thermal lens signal (TLs) was monitored with a He-Ne laser beam and a photodiode detector. Multichannel averager software was developed for processing the transient TLs. The optimal set up, ensuring maximum sensitivity and linear calibration graphs was obtained using experimental design techniques. Under optimized conditions, the detection limits for aqueous and ethanol-water (2+3 v/v) and (4+1 v/v) vanadium complex solutions were, respectively, 0.0071 mg/l, 0.0065 and 0.0039 mg/l.
Nanoparticles with optical and magnetic responses are of great applicability in different fields.... more Nanoparticles with optical and magnetic responses are of great applicability in different fields. In this work, zero valent iron nanoparticles were prepared by laser ablation and stabilized in a surfactant solution to keep particles dispersed and protected in the solution. Optical and magnetic properties of nanoparticles were measured, by UV and Mössbauer spectroscopy. The results show the formation of nanoparticles of a-Fe (ferromagnetic). Our method of preparation, which uses a high H + concentration in the medium, diminishes the zero valent iron oxidation, producing iron nanoparticle with a core of a-Fe and a small shell probably composed of iron oxides.
Nanoparticles with optical and magnetic responses are of great applicability in different fields.... more Nanoparticles with optical and magnetic responses are of great applicability in different fields. In this work, zero valent iron nanoparticles were prepared by laser ablation and stabilized in a surfactant solution to keep particles dispersed and protected in the solution. Optical and magnetic properties of nanoparticles were measured, by UV and Mössbauer spectroscopy. The results show the formation of nanoparticles of α-Fe (ferromagnetic). Our method of preparation, which uses a high H + concentration in the medium, diminishes the zero valent iron oxidation, producing iron nanoparticle with a core of α-Fe and a small shell probably composed of iron oxides.
The present work studied the effects of crude oil solution concentration, reservoir temperature, ... more The present work studied the effects of crude oil solution concentration, reservoir temperature, and n-heptane addition flow rate on asphaltenes flocculation onset by using an automatic titration system. These effects were evaluated through the application of a central composite design that allows the simultaneous evaluations of the experimental parameters under study. Results showed that the onset measurements were strongly affected by the crude oil solution concentration, mainly on unstable crude oil samples. This phenomenon can be used to estimate the crude oil stability. On the other hand, temperature of the sample reservoir and precipitant addition showed a slight effect on the flocculation onset.
This work presents a new surface plasmon resonance (SPR) instrument based on Kretschmann configur... more This work presents a new surface plasmon resonance (SPR) instrument based on Kretschmann configuration. This device acquires and processes the reflected SPR image of the sample by using a webcam together with an image processing algorithm that transforms the RGB image in numeric values and correlates the integrated intensity with the refractive index of the solution. Experimental signals were compared with theoretical values and it was found an excellent agreement. In addition, the applicability of the instrument was tested by measuring the refractive index of solutions in a continuous flow mode. Excellent stability and sensitivity of the signal were found in the presence of small changes of the refractive index.
Biochemical analysis and clinical tests like glucose, hemoglobin, cholesterol, iron, etc. are cru... more 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.
In this work, we measure the refractive index of crude oils and asphaltene in toluene solutions u... more In this work, we measure the refractive index of crude oils and asphaltene in toluene solutions using a fiber optic refractometer designed to work with high-viscosity and high optical density samples. The data of the samples were analyzed using the Lorentz−Lorenz theory and ...
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