Desenvolvimento de uma metodologia analítica em fluxo para determinação espectrofotométrica de fluoreto em águas naturais pelo método de SPADNS

Abstract

An environmentally-friendly flow system was developed for the determination of fluoride in natural waters, based on its reaction with zirconium ions and trisodium salt of acid 1,8-dihydroxy-2-(4-sulfophenylazo)-3,6-naphthalene-disulfonate (SPADNS). The flow system was designed with solenoid valves in order to increase the versatility and improve the analytical performance, since each device handles the solution independently leading to more efficient use of reagents. The minimization of reagent consumption and waste generation favors the development of a system based on the principles of Green Chemistry. Under optimized conditions, a linear response was observed within the range of 0.1 2.2 mg L-1, with the detection limit, coefficient of variation and sampling rate estimated as 0.02 mg L-1, 4.1% and 60 determinations per hour, respectively. In comparison with other methods, the proposed system offers advantages such as wider analytical range (1.7 to 2.2 times), higher sample throughput (1.5 to 4.0 times), and quantification limit (by a factor of 5 to 68). Along with the consumption of reagents being 20 to 55 times lower and the generation of wastes is 1.2 to 3.0 times lower, which contributes to the development of a greener system. This method is fast, amenable to automation, environmentally-friendly and of low-cost, and it could be successfully applied to the determination of fluoride in water samples, the results obtained being in agreement with those of the ion selective electrode (ISE) method.