Determination of Cobalt in Food and Water Samples by Ultrasound-assisted Surfactant-enhanced Emulsification Microextract
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Determination of Cobalt in Food and Water Samples by Ultrasound-assisted Surfactant-enhanced Emulsification Microextraction and Graphite Furnace Atomic Absorption Spectrometry Pei Liang & Juan Yu & Enjian Yang & Yajuan Mo
Received: 16 September 2013 / Accepted: 28 November 2013 # Springer Science+Business Media New York 2013
Abstract A novel method based on ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) has been developed for the preconcentration of cobalt prior to its determination by graphite furnace atomic absorption spectrometry. In the UASEME technique, chloroform was used as the extraction solvent, sodium dodecyl sulfate was adopted as emulsifier, and ultrasound was applied to assist emulsification. There is no need of using organic dispersive solvent which is typically required in conventional dispersive liquid–liquid microextraction method. Several parameters that affect the extraction efficiency, such as the kind and volume of the extraction solvent, the type and concentration of the surfactant, pH of sample solution, concentration of the chelating agent, and extraction time and temperature were investigated and optimized. Under the optimal conditions, the linearity of calibration curve was in the range of 0.1– 5 ng mL−1 with a correlation coefficient (R 2) of 0.9992. An enrichment factor of 58 was achieved with a sample volume of 5.0 mL. The detection limit of this method for Co was 15.6 ng L−1, and the relative standard deviation (RSD) was 4.3 % at 1.0 ng mL−1 concentration level of Co. The accuracy of the developed method was evaluated by analysis of the certified reference materials GBW07605 tea leaf and GBW10015 spinach. The method was successfully applied to determine trace cobalt in food and water samples with satisfactory results.
P. Liang (*) : J. Yu : E. Yang : Y. Mo Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, People’s Republic of China e-mail: [email protected]
Keywords Ultrasound-assisted surfactant-enhanced emulsification microextraction . Graphite furnace atomic absorption spectrometry . Cobalt . Food and water samples
Introduction Cobalt (Co) is an essential element for human health because it is an important co-factor in vitamin B12dependent enzymes and an indispensable component in a number of enzymes (Battersby 1993; Kobayashi and Shimizu 1999). Being a component of vitamin B 12 (cyanocobalamin), it plays an important role in the production of erythropoietin and has been used medically for the treatment of anemia (Barceloux 1999). However, exposure to high levels of Co can result in lung and heart effects and dermatitis, as was shown in several outbreaks of cardiomyopathy among heavy drinkers of beer to which Co had been added (Alexander 1972). Food and drinking water are the largest sources of exposure to Co for the general population. The maximum recommended concentration of Co in fresh water for livestock is 110 μg L−1 (http://www.env.gov.bc.ca
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