Métodos automáticos para a especiação de antimônio inorgânico em águas e determinação de antimônio total em sucos de uva por espectrometria de fluorescência atômica

Abstract

This research paper addresses the development of automatic methods for inorganic antimony speciation and total antimony determination. Unpublished coupling of the flow-batch system, hydride generation and atomic fluorescence spectrometry was named the FBA-HG-AFS method. The first methodology was developed for inorganic Sb speciation in aqueous samples. The method was optimized using a full factorial design and Box-Behnken matrix. The factors involved in the optimization were the carrier gas flow and the concentrations of hydrochloric acid (HCl) and sodium borohydride (NaBH4). The optimized experimental conditions allowed the determination of Sb between 100 and 2.000 ng L-1, where the detection and quantification limits were 6 and 20 ng L–1, respectively. The accuracy of the proposed method was confirmed by analysis of certified reference material (SRM 1643e) and recovery tests for Sb(III) and Sb(V) (90 - 114%). The method for water analysis showed sample throughput of 54 speciation per hour, accompanied by low consumption of samples and reagents as well as low waste generation. The proposed method was applied to three samples of mineral water, one tap water, one pond water and one sea water in the city of Maceió, Alagoas. The results of the analyzes showed that the concentrations ranged from 140 ± 20 to 430 ± 30 ng L-1 for Sb (III), from 210 ± 30 to 990 ± 90 ng L–1 for Sb (V) and from 350 ± 20 to 1.410 ± 90 ng L–1 for total Sb. The second method proposes the automatic direct determination of total Sb in grape juice samples using the FBA-HG-AFS system. The HCl was more suitable for the extraction of Sb, providing extraction in a time of 5,0 s. The optimization step was carried out employing a Box-Behnken matrix where the concentration of HCl, NaBH4 and argon flow were the factors studied. Under the optimized conditions, an analytical curve of 0,1 to 2,0 μg L–1 was constructed and presented detection and quantification limits of 0,02 and 0,066 μg L–1, respectively. The accuracy of the method was confirmed with recovery tests, which ranged from 88,8 ± 1,5 to 116,2 ± 1,2 % for total Sb. The method showed no significant difference at a level of 95% confidence compared to the reference procedure. The total antimony concentrations found ranged from 1,23 ± 0,05 to 4,58 ± 0,1 μg L–1 in samples of grape juices acquired in the city of Maceió, Alagoas, presenting lower relative standard deviation (RSD %) less that 3.7%. Finally, the system presented an analytical frequency of 87 h-1 and low residue generation.