Automation and miniaturization of liquid-liquid extraction applied for determination of thiocyanate in human saliva

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

Santa Fe

Congreso; VI Congreso Argentino de Química Analítica; 2011

Asociación Argentina de Químicos Analíticos

Liquid-liquid extraction (LLE) is one of the most widely used sample pre-treatment techniques in analytical chemistry. However, the manual application of this technique demands long analysis time and requires the use of large volumes of solvent which increases costs, besides being harmful to the user and the environment [1]. Therefore, the search for new alternatives to conventional LLE, using small volumes of organic solvent, ensuring high accuracy, repeatability of measurements and short pre-treatment remains a challenge and innovations in this area are attractive [2]. In this sense, a new dual-valve sequential injection (DV-SIA) system [3] with the online incorporation of a LLE cell into the SIA manifold has been constructed. The SIA system is simple and it easy implements precise manipulation of the solutions in the flow system. One of its main advantages is its versatility for the determination of different analytes in different types of samples and using different solvents. In this work, the extraction and spectrophotometric determination of thiocyanate ions concentration in human saliva samples using the SIA methodology was carried out. The method was based on the reaction of thiocyanate ions with astraphloxine in acidic medium (pH 3) and the subsequent extraction of the coloured associate ion with amylacetate. The measurements of absorbance were done at 550 nm. The physical and chemical variables of the SIA system were optimized. The results were compared with those obtained in batch conditions, in terms of analysis time, solvent consumption, accuracy, repeatability, detection and quantitation limits. The method was applied to thiocyanate determination in human saliva samples obtained from different day times, and validated by a recovery study. This work has been supported by 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 acknowledged financial support of her scholarship in research fellowship program between Ministries of Education of Argentina and the Czech Republic, and CONICET. [1] Miro, M.; Hansen, E. Advances in Flow Methods of Analysis, Wiley-VCH, Weinhem (2008). [2] Silvestre, C.; Santos, J.; Lima, J.; Zagatto, E. Anal. Chim. Acta 652 (2009) 54. [3] ?krlíková J.; Andruch V.; Sklenářová, H.; Chocholou?, P.; Solich, P.; Balogh, I. Anal. Chim. Acta 666 (2010) 55.