Feasibility of calcium alginate beads to preconcentrate lead in river water samples prior to determination by flame atomic absorption spectrometry.

Lead (Pb) is a potentially toxic element with significant environmental interest. Simple and sensitive analytical methods are necessary to allow determination of this element at trace levels using sample preparation procedures related to green chemistry. For this, calcium alginate beads (CA-beads), a low-cost and environmentally friendly biopolymer, have been proposed for extraction and preconcentration of Pb in river water samples and determination by flame atomic absorption spectrometry (FAAS). CA-beads were prepared and applied to extract and preconcentrate Pb in river water samples, providing an enrichment factor (EF) of 50, enhancement factor (E) of 54, a detection limit of 2 μg L, and a relative standard deviation < 5%. The extraction of Pb in CA-beads achieved good selectivity, with recoveries from 94.8 to 100.2% in real samples, demonstrating the good accuracy of the proposed method. The results were also compared to those obtained by ICP-MS. The reuse of CA-beads was evaluated for six cycles, and under these conditions, the extraction and preconcentration efficiency of Pb were not significantly affected. The developed methodology was applied to determine Pb in water samples from rivers that are part of the hydrographic areas of Tibagi and Pitangui Rivers, in which the Pb concentration was less than 2 μg L, a concentration lower than that established by Brazilian legislation for class I and II rivers.