Metodologia analítica baseada em µPAD para determinação simultânea do Hg(II) e Pb(II) em águas naturais do rio São Francisco da cidade de Penedo

Abstract

In recent years, there has been a growing ecological and global public health concern associated with environmental contamination by potentially toxic metals, as metal ions such as Hg2+ and Pb2+ enter ecosystems as chemical species dissolved in water systems and fall into the category of human carcinogens, and non-biodegradable pollutants, resulting in harmful effects on health, genetics, nutrition and ecosystems. Therefore, the development of a device capable of identifying and quantifying the concentration of these analytes is of paramount importance. Thus, in this work, an analytical device based on in loco test paper for the simultaneous determination of Hg2+ and Pb2+ in samples of natural waters from the São Francisco River in the riverside town of Penedo is presented. Paper-based analytical microdevices (µPADs) were associated with colorimetric detection, based on the reaction between the analytes in question and the dithizone colorimetric probe, generating a color proportional to the concentration of these metals. It was observed that the system behaves better at pH=9.0, with a boric acid buffer solution. In this work, the influence of the color channels of the RGB scale (Red, Green and Blue) was studied, it was observed that for the method proposed in this work the red channel presented the best result for both metals. The stability of the color presented in the devices was verified, with a variation of only 5% and 10% in a time interval of 4h in the presence of Hg2+ and Pb2+, respectively. In addition, low interference was obtained from potentially toxic metals (Na+ , K + , Fe3+ ,Mn2+, Zn2+ and Cu2+) that can be found in water samples, which indicates good selectivity for both analytes. Of the four types of layouts discussed in this work, the device 04 stood out, as it presented the best result due to its width, drying time and volume of reagents. In the evaluation of linearity, the values of the red channel had a correlation greater than 0.989 for mercury and 0.991 for lead. The detection limit determined was LOD=0.82 µg/mL and quantification was LOQ= 1.12 µg/mL, with a linear range of 1 – 20 µg/mL for mercury, and for lead the values found were of LOD= 0.89 µg/mL; LOQ= 5.35 µg/mL and linear range of 5 - 30 µg/mL. Therefore, this methodology proved to be suitable for application in natural water samples. It is a simple, cheap and fast alternative for the determination of Hg2+ and Pb2+. .