AVANCESCuantificación de cationes metálicos en agua con LIBS por deposición sobre una superficie de acero rayada con lápiz HB Diego Jijón 1 * César Costa Vera
AbstractThe use of laser-induced breakdown spectroscopy (LIBS) together with a pencil lead substrate for the quantitative analysis of salts dissolved in liquids provides is introduced as a very efficient and sensitive analytical method. In this work we have compared five substrates over which aqueous solutions of salts were left to dry, and then submitted for analysis with LIBS. The comparison was based in analytical parameters such as the sensitivity and linearity of each substrate. We found that from these, the surfaces of graphite and a steel surface scratched with pencil HB gave the best results. The concentration of the salt (cation) in the solution was made to correspond to the areas of specific peaks for each corresponding atom. In this work, we used a method introduced by Jijón et al. [1] for data handling. This spectra selection method produces better linearity in calibration curves and much smaller errors that translate into correlation coefficients closer to 1, in this work correlations index up to 0.98 were determined. We introduced an experimental setup with mirrors to study the self-absorption effect, showing in this work the lost of linearity in the peak areas at high concentrations. We observed an indentation in the center of the Cs and K peaks, and the lost of signal LIBS of the spectrum of each peak analyzed with mirrors. In the last part of this work, we applied the methodology for quantification introduced to quantification of arsenic dissolved in water, as a real life application for concentrations until 1000 ppm. The non linear calibration curve for the whole range in this case was fitted to an exponential function with 0.993 of correlation index. The detection limit calculated for the arsenic in water was 3.2 ppm and this result is very satisfactory compared with those reported on literature for LIBS.
Keywords. LIBS, quantitative analysis, LIBS quantification, liquid analysis.
ResumenEn este trabajo se introduce la aplicación de LIBS(Laser-induced Breakdown Spectroscopy) junto con un substrato novedoso de acero rayado con lápiz HB para el análisis cuantitativo de sales disueltas en líquidos provistas como un método analítico eficiente y sensitivo. Para esto, se han comparado cinco substratos sobre los cuales se dejaron secar soluciones en agua de sales, cuyos depósitos se analizaron posteriormente con LIBS. Las comparaciones se basaron en parámetros analíticos tales como sensitividad y linealidad. Se encontró que de éstas, las superficies de grafito y la de acero rayado con lápiz HB dieron los mejores resultados. La concentración de la sal (catión) en la solución se hizo corresponder con áreas de picos específicos para cada átomo. En este trabajo se utilizó un método estadístico introducido por Jijón et al.[1] para el tratamiento de los datos. Este método de selección de espectros produce una mejor linealidad en las curvas de calibr...
