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  • Author or Editor: J. R. Estévez Álvarez x
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Abstract  

The aim of this work consisted on the implementation of sufficiently accurate and sensitive analytical procedure for the analysis of metal concentration in rainwater. Different sample preparation procedures were tested to achieve the required concentration prior to direct total reflection X-ray fluorescence (TXRF) analysis. TXRF and anodic stripping voltammetry (ASV) were compared in regard to achieved detection limits, precision and accuracy.

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Abstract  

“Cut-off” reflectors, which allow obtaining a reflected beam with almost no high energy radiation, as well as different monochromator devices that reflect a beam of monoenergetic and polarized radiation are the most widely employed artifacts to perform the excitation radiation improvement in analytical “non-expensive” TR spectrometers. The aim of this work consisted in testing several monochromator devices: a multilayer structured mirror for soft X-rays (0.7–12.5 nm), as well as different bent and flat crystals of wavelength dispersive spectrometers. The achieved instrumental detection limits for the selected monochromator device are compared with the values obtained using a Suprasil Cut-off reflector and a C-W multilayer (d∼5 nm). Several human corporal fluid samples were analyzed to compare the spectral characteristics when using the Cut-Off Reflector and the RAP flat crystal, respectively.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Montero Alvarez, J. R. Estévez Alvarez, H. Iglesias Brito, O. Pérez Arriba, D. López Sánchez, and H. T. Wolterbeek

Summary  

An epiphytic lichen (Physcia alba sp.) grown over Roystonea regia tree was used as biomonitor of air quality in the Havana City west side. During the survey, 81 sampling sites were selected according to traffic and industry conditions. The concentration for 14 elements (Mg, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Cd and Pb) was determined by flame atomic absorption spectrometry (FAAS) and anodic stripping voltammetry (ASV). Contents of Cu, Zn, Cd and Pb obtained by both techniques were compared. Several biological reference materials (RM's) were analyzed in order to assure the quality of analytical results. Some pollution sources were identified using principal component analysis. A total of 5 factors were achieved, of which 4 could be interpreted in terms of anthropogenic pollution sources. However, the expected correlation between traffic influence and lead concentration in lichen could not be demonstrated. The factor values patterns are presented.

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Abstract  

Several studies on the influence of heavy metals to the growth of vegetables have been carried out in Cuba by the Ministry of Agriculture in order to evaluate the effects resulting of the continuous application of fertilizers and other materials to the soils. The analysis of metal contents in soil and vegetable samples is often troublesome due to the low concentration levels to be determined. In the the present work EDXRF, AAS and ASV methods were applied and compared for the evaluation of Cr, Ni, Cu, Zn, Cd and Pb contents in red ferralitic soil and Sorghum samples. Several certified reference materials (CRM) (inorganic and organic matrixes) were analyzed in order to evaluate the performance of the analytical procedures and the bias and precision of the results. A study was performed with growing Sorghum in several series of pots where different quantities of metals were added to the soil substrate. The observed correlation between the metal contents in soil and plants as well as the influence of different additions of each metal on the plant growth is also presented.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: N. Alberro Macias, I. Pupo González, L. Valcárcel Rojas, D. Frías Fonseca, J. R. Estévez Álvarez, D. López Sánchez, A. Montero Álvarez, D. Simón Pérez, M. A. Isaac Tejera, and J. F. Pérez Oliva

Summary  

The quality of the potable and purified for haemodialysis waters used in the National Institute of Nephrology was evaluated since 2002 up to now. A total of 20 chemical components were analyzed. The analytical results were compared with the admissible maximum concentrations according to the Cuban Standard NC 92-02:85 for potable water and with the Spanish Standard UNE 111-301-90, related to the quality of water for use in haemodialysis. The quality of both types of water was found to comply with the Standards regulations. The CEADEN analytical chemistry laboratory operates a quality management system since 1992, that was credited according to ISO/IEC 17025 requirements.

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