WUILLOUD Rodolfo German
congresos y reuniones científicas
Application of a design of experiments for the optimization of a microextraction procedure based on ionic liquid as ion-pairing agent for chromium species separation and determination in water samples
BERTON, PAULA; VERA-CANDIOTI, LUCIANA; GOICOECHEA, HECTOR C.; WUILLOUD, RODOLFO G.
Foz do Iguaçu
Simposio; TWELFTH RIO SYMPOSIUM ON ATOMIC SPECTROMETRY; 2012
TWELFTH RIO SYMPOSIUM ON ATOMIC SPECTROMETRY
The two oxidation states of chromium (Cr) most commonly present in aqueous solution, i.e. Cr(III) and Cr(VI), differed drastically in its physiological and toxicological effects, its chemical transformations as well as its distribution and transport in the environment.1 Moreover, since concentration of total Cr in surface waters can be very low, considerable emphasis has been given to the development of analytical methodologies for Cr species separation and determination. Ionic liquids (ILs) are a new generation of fluids, considered as green solvents which, among other applications, have been proposed for separation processes.2 Recently, the IL trihexyl(tetradecyl)phosphonium chloride (CYPHOS® IL 101) has been proposed as ion-pairing reagent for metal extraction from aqueous phases.3, 4In the present work, a novel methodology for speciation analysis was developed with initial ion-pairing of Cr(VI) with CYPHOS® IL 101. After ion-pair formation, a simple and rapid microextraction procedure named ultrasound-assisted emulsification-microextraction (USAEME) was employed for Cr species separation and preconcentration. Determination of Cr was performed by direct injection of the organic phase into the electrothermal atomic absorption spectrometer (ETAAS). Selectivity among Cr species was achieved by pH control. Total Cr was determined after oxidation of Cr(III) to Cr(VI) by hydrogen peroxide. A Plackett?Burman screening design and a central composite design were used to optimize the operational conditions for the procedure. The combination of microextraction and chemometrics significantly simplify sample processing, and also addresses problems related to improvement in detectability and method validation.5 Under optimum conditions, the analyte extraction efficiency was higher than 99% and yielded a preconcentration factor of 250 with only 10 mL of sample. The limit of detection obtained was 2.4 ng L−1 and the relative standard deviation for 10 replicate determinations at the 0.1 µg L−1 Cr level was 4.8%, calculated at peak areas. A correlation coefficient of 0.9983 was achieved. The method was successfully applied for ultratrace determination of Cr species in tap and river water samples.1. Metze, D., et al., Speciation of Chromium. In Handbook of Elemental Speciation II - Species in the Environment, Food, Medicine and Occupational Health, Cornelis, R., Ed. John Wiley & Sons, Ltd: Chichester, 2005; p 768.2. Han, D., et al., Molecules,15(4):2405,2010.3. Escudero, L. B., et al., Talanta,88(1):2012.4. Stojanovic, A., et al., Quaternary Ammonium and Phosphonium Ionic Liquids in Chemical and Environmental Engineering. In Ionic Liquids: Theory, Properties, New Approaches, Kokorin, A., Ed. InTech: 2011; pp 657-680.5. Stalikas, C., et al., J Chromatogr A,1216(1):175,2009.