Automation of liquid-liquid extraction procedure in the DV-SIA system - Determination of thiocyanate

CAROLINA ACEBAL; IVANA SRÁMKOVÁ; HANA SKLENÁROVÁ; JANA SKRLÍKOVÁ; VASIL ANDRUCH; IOSEPH S. BALOGH; PETR SOLICH

Cracovia

Conferencia; 17th International Conference on Flow Injection Analysis; 2011

Liquid-liquid extraction (LLE) is one of the most widely used sample pre-treatment techniques in analytical chemistry. The search for alternatives to the conventional LLE, using small volumes of organic solvent, ensuring high precision, repeatability of measurements and the minimum number of steps as possible still remains a challenge and innovations in this topic are attractive [1]. In this sense, a simple, user-friendly and universal dual-valve sequential injection (DV-SIA) system [2] with the online incorporation of LLE cell into the SIA manifold have been constructed. One of the advantages of this system variability of samples and organic solvents that could be used and analysed in the same system. In this work, the optimization of the physical and chemical parameters for the extraction and the spectrophotometric determination of thiocyanate ions, in batch conditions and using the previously reported DV-SIA manifold, was carried out. The method is based in the reaction between thiocyanate ions and astraphloxine dye to form a coloured complex that is extracted with amylacetate. In automated DV-SIA system an air-assisted LLE [3], not commonly applied in analytical chemistry, was presented for this system. The air is introduced into the system like any other reagent, at the beginning of the aspiration sequence, and then delivered into the extraction cell to carry out the mixing and extraction. For thiocyanate determination, 50 µL of astraphloxine 2x10-3 M, 10 µL of ammonium/ acetate buffer pH 3, 50 µL of sample and 350 µL of amylacetate were aspirated and delivered into the extraction cell with 700 µL of air. The detection of the complex was done at 550 nm. The optimal values were chosen taking into account the highest value of the analytical signal and the lowest RSD value obtained. Optimized reaction procedure in batch and flow conditions were compared with respect to analysis time, solvent consumption, precision, repeatability, limit of detection and quantitation. This work has been supported by the Charles University in Prague (Project SVV 263 002), and the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences VEGA (Grant No. 1/0226/11). C. Acebal has acknowledged financial support of her scholarship in research fellowship program between Ministries of Education of Argentina and the Czech Republic. References [1] C. Silvestre, J. L. M: Santos, J. L. F. C. Lima, E. A. G: Zagatto, Analytica Chimica Acta 652 (2009) 54. [2] J. ?krlíková, V. Andruch, H. Sklenářová, P. Chocholou?, P. Solich, I.S. Balogh, Anal. Chim. Acta 666 (2010) 55. [3] J. ?krlíková, V. Andruch, H. Sklenářová, P. Chocholou?, P. Solich, I.S. Balogh, Anal. Methods 2 (2010) 1134.