Ultra-Trace Determination of Co (ІІ) in Real Samples Using Ion Pair-Based Dispersive Liquid-Liquid Microextraction Followed by Electrothermal Atomic Absorption Spectrometry

Author:
, , , , ,
Year
: 2016
Abstract: Ion pair-based dispersive liquid-liquid

microextraction technique was used for preconcentration and

determination of ultra-trace levels of Co (ІІ) followed by electrothermal

atomic absorption spectrometry (ETAAS). Thiocyanate

(SCN−) forms an anionic complex with Co (ІІ) followed

by addition of cetylpyridinium chloride (CPC) as a positive

counterion to produce hydrophobic cobalt-thiocyanate-CPC

complex. The resulting hydrophobic complex was extracted

into the fine droplets of carbon tetrachloride by dispersive

liquid-liquid microextraction (DLLME). In DLLME, a mixture

of 1.5 mL of acetone (as disperser solvent) containing

40 μL of carbon tetrachloride (as extraction solvent) was rapidly

injected into the sample solution to extract the hydrophobic

cobalt-thiocyanate-CPC complex. Under the optimum

conditions, the calibration curve was linear in the range of

0.08–1.5 μg L−1 of Co (ІІ) with a correlation coefficient of

0.9997. The relative standard deviation (RSD, %) based on six

replicate analyses of 0.5 μg L−1 of Co (ІІ) was 3.7 %, and the

limit of detection (LOD) was 0.02 μg L−1. The accuracy of the

proposed method was evaluated by the analysis of a certified

reference material and spike method. The proposed method

was successfully applied for determination of ultra-trace levels

of Co (ІІ) in different water samples and spinach leaves.
Keyword(s): Cobalt,Preconcentration,Thiocyanate anion,

Ion pair-based dispersive liquid-liquid microextraction
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