Ionic liquid-assisted speciation studies of cobalt in nutritional supplements by temperature-controlled dispersive liquid phase microextraction prior to electrothermal atomic absorption spectrometry

P. BERTON; L. B. ESCUDERO; R. G. WUILLOUD

São Paulo

Encuentro; 16th ANALYTICAL CHEMISTRY NATIONAL MEETING (160ENQA); 2011

Universidad Nacional de Sao Paulo

One of the most important molecules occurring in food and medicine is vitamin B12. Although the availability of numerous analytical methods for vitamin B12 determination, several drawbacks, such as laboriousness, time-consuming, low selectivity, unsafe, high cost and low sensitivity, are usually mentioned in the literature. Therefore, continuous efforts are required to overcome these limitations. Ionic liquids (ILs) bring beneficial properties compared to organic solvents like nonflammability and nonvolatility. However, the high viscosity of the IL phase could induce denaturation during extraction/separation of biomacromolecules using simple IL/water biphasic systems. State-of-the-art techniques based on application of ILs in aqueous two-phase systems (IL-ATPSs) have been recently proposed by some research groups for high recovery and purification of several biomolecules. In the present work, a novel and simple microextraction technique based on ATPS, involving 1-hexyl-3-methylimidazolium chloride, a hydrophilic IL, and K2HPO4 was developed for simultaneous separation, and enrichment of vitamin B12 in nutritional and biological samples. After microextraction procedure, the vitamin B12-enriched RTIL upper phase was directly injected into the high performance liquid chromatography (HPLC) system for analysis. All variables influencing the IL-based ATPS approach (e.g., the composition of ATPSs, pH and temperature values) were evaluated. Average extraction efficiency was higher 95% under optimum conditions. Only 5.0 mL of sample and a single hydrolysis/deproteinization/extraction step were required, followed by direct injection of the IL-rich upper phase into HPLC system for vitamin B12 determination. A detection limit of 0.09 µg/mL, a relative standard deviation (RSD) of 4.5% (n = 10) and a linear range of 0.4-8 µg/mL were obtained. The proposed method was satisfactorily applied to the analysis of samples with highly complex matrices, such as urine and supplemented beverages. The suggested IL-ATPS technique could be considered therefore as a potential watersoluble vitamin extraction system.