Biomedical subjects

Andrea Buzády

Publications and source records attributed to Andrea Buzády.

4 recordsLinked to original sources

PubMed2006

Determination of uranine tracer dye from underground water of Mecsek Hill, Hungary.

The underground water system of Mecsek Hill, Hungary was studied using spectrofluorometry. A quantitative dye-tracing technique was used to map the connections between ground water recharge points and the springs and wells. Excitation-emission matrices were used to establish optimal spectroscopic parameters for spectral measurements. Only an EEM gives full spectrofluorimetric information about the sample and makes possible the determination of the optimal wavelength parameters. The uranine concentration was determined by measuring the synchronous excitation spectra of water samples. It was found that under the 4 microg/L uranine concentration, no special chemical treatment was necessary if the pH values remained between 7 and 8. However, above this concentration, the solution should be diluted to avoid spectral distortion from the increasing absorbance of the sample. Long-term concentration measurements were conducted based on spectrofluorometry.

Fluorescein↗

PubMed2006

Comparative study of integrating cavity absorption meters.

Integrating spheres (IS) are widely used for recording spectra of scattering samples by placing the specimen inside or outside the sphere. An unusual application of integrating spheres has been also demonstrated earlier where the liquid sample completely filled the spherical cavity; such a device is often called an integrating cavity absorption meter (ICAM). In the present work, integrating cavities with different coatings are compared. The spheres were made of glass, covered by metal or white paint, and their surfaces were prepared for diffuse or specular reflectance. The spheres were evaluated by recording kinetic traces following a short light pulse with the aid of time-correlated single photon counting (TCSPC), and by recording steady-state spectra through single-photon counting (SPC) detection. The relative efficiencies of the spheres were determined by comparing the steady-state spectra. Possible reasons for differences in the performance are discussed.

Absorption↗

PubMed2006

Relation between fluorescence decays and temporal evolution of excited states.

A differential equation system describing the temporal evolution of excited substates and fluorescence emission were tested using a DOPRI algorithm. The numerical solutions show that there is significant difference in the measurable parameters according to the type of connectivity among the excited substates. In the globally connected case, the fluorescence emission exhibits a double exponential behavior, and the first moment of the emitted spectrum decays with stretched exponential characterized by beta < 1. In the diffusive case the fluorescence emission cannot be always fitted with double exponential, and the first moment of the emitted spectrum may decay with stretched exponential characterized by beta > 1. Details of modeling and the possibilities of drawing conclusions are also presented.

Journal Article↗

PubMed2005

Quantitative spectrophotometry using integrating cavities.

Absorption spectrophotometry, a standard tool for quantitative analysis, suffers from two major drawbacks: lack of sensitivity and vulnerability to scattering. It has been pointed out earlier that the solution to these problems lies in using a reflecting cavity as a sample holder. Due to multiple reflections at the cavity wall, the effective pathlength becomes considerably larger than the diameter of the cavity, and scattering losses are eliminated because scattered light is prevented from escaping the detector. Though much effort has been spent in analysing and improving the performance of such a device, often called an integrating cavity absorption meter (ICAM), a simple strategy for deducing the absorbance of the sample is still lacking. It is shown here that the absorbance A' measured by using an ICAM exhibits a sublinear increase with the solute concentration C. The physical reason for this departure from linearity is explained, and a straightforward procedure for converting A' to the true absorbance A (proportional to C) is established. The reliability of the procedure is demonstrated by comparing the ICAM absorption spectrum of dilute dye solutions with the spectra of more concentrated solutions recorded in a conventional spectrophotometer. The ability of the device to cope with scattering was tested by filling the ICAM with a suspension of chloroplasts, and the spectrum was found, as expected, to be free from scattering artefacts.

Calibration↗