Análisis de especiación ultrasensible de especies inorgánicas de antimonio en muestras de agua mediante microextracción líquido-líquido dispersiva con la implementación de un líquido iónico magnético y detección por espectrometría de absorción atómica ele

FIORENTINI, EMILIANO F.; OVIEDO, MARÍA N.; WUILLOUD, RODOLFO G.; LEMOS, ALDANA A.

DF

Congreso; LatinXChem (Congreso de Química en Twitter); 2020

Cinvestav Unidad Mérida

Antimony is a toxic element present in the environment from natural (e.g. volcanic activity) and anthropogenic sources (e.g. industry)1. It is well known that the toxicity of inorganic Sb species is higher than organic Sb compounds. Moreover, Sb(III) is at least 10 times more toxic than Sb(V) species, therefore, speciation analysis of this element is very important. The natural concentration of total Sb in surface water is usually less than 5 µg L-1, while the concentrations of the different Sb species are in order of ng L-1. However, these low concentrations are not compatible with the limits of detection (LODs) reached by some detectors based on atomic spectrometry. Therefore, the development of sensitive analytical methodologies for preconcentration and speciation of Sb at trace levels is required. Ionic liquids (ILs) have been widely used as solvents in liquid-liquid microextraction techniques (LLME). Recently, a new group of ILs known as magnetic ionic liquids (MILs) has become the subject of interest in several analytical applications because they strongly respond to external magnetic fields and show the unique and tunable physicochemical properties of ILs3.In the present work, a novel analytical method based on the DLLME technique using the MIL trihexyl(tetradecyl)phosphonium tetrachloroferrate ([P6,6,6,14]FeCl4) was developed for selective extraction and preconcentration of Sb(III). Ammonium diethyldithiophosphate (DDTP) was used as complexing agent and detection of Sb was performed by electrothermal atomic absorption spectrometry (ETAAS). In this method, Sb(III) was complexed with DDTP adjusting the acidity of aqueous samples at 2 mol L-1 HCl, followed by the extraction of Sb(III)-DDTP complex with 45 µL of the MIL, and the addition of acetonitrile and NaCl to disperse the extractant phase and to increase the ionic strength, respectively. After vortex stirring, the MIL phase was collected with a magnetic rod and diluted in 140 µL of CHCl3. Then, 15 µL of this solution was injected into the graphite furnace of ETAAS for Sb determination. A multivariate study was performed to obtain the optimal extraction conditions. Selective reduction of Sb(V) to Sb(III) species was performed before pre-concentration to determine total inorganic Sb. Thus, the concentration of Sb(V) was obtained by the difference between total inorganic Sb and Sb(III) concentration. The analytical performance of the method developed in this work included extraction efficiencies of 98% for Sb(III) and 92.6% for Sb(V), LODs of 0.02 µg L-1 for Sb(III) and 0.05 µg L-1 for Sb(V) and relative standard deviations of 3.1% for Sb(III) and 3.5% for Sb(V) (for a 7 µg L-1 Sb(III) and Sb(V) solutions, n=10). The proposed methodology was successfully applied to natural water samples (lake and river).