Background: Cobalt is one of the most important essential trace metals of human nutrition.
Low doses of cobalt are needed for many humans and animals to stay healthy. Cobalamine (named vitamin
B12) is a cobalt-containing essential vitamin. The direct detection of metal ions in various matrices
by AAS may be difficult due to matrix interferences and extremely low levels of metal ions. Thus, a
preconcentration and separation step is normally demanded. In this report, a two-step microextraction
technique, combining room temperature ionic liquid based dispersive liquid-liquid microextraction (ILDLLME)
and dispersive magnetic solid-phase microextraction (MSPME) was prepared for the flame
atomic absorption spectrometric determination (FAAS) of trace cobalt ions in water samples.
Methods: In this study, a two-step microextraction technique based on a new combined approach of ILDLLME/
M-SPME was discussed and the proposed method was applied to the rapid determination of
trace cobalt ions in various water samples. In this study, room temperature IL-1-ethyl-2,3- dimethylimidazolium
bis(trifluoromethyl sulfonyl)imide [EMIM][Tf2N] was employed as an extractant in the first
extraction step (i.e. DLLME). This combined technique offers low limits of detection and high preconcentration
factors resulting in high sensitivity. The reported method described an amazing and innovative
approach of combining different microscope sample preparation methods to solve some analytical
Results: In the first microextraction step, room temperature ionic liquid (RTIL) was employed to extract
cobalt-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) complexes from aqueous solution
with ultrasound. In the second step, magnetic Fe3O4 NPs was added as an adsorbent and employed to
collect the analytes in the organic solvent. After magnetic solid phase separation, the concentrated analyte
complexes were eluted with 0.1 M HCl. As a consequence, the linear working range was 0.1-250
µg/L, and the detection limit of the method (LOD) was estimated to be 0.05 µg/L. The proposed twostep
extraction procedure was employed by analysis of a certified reference and real water samples.
Conclusion: In the current study, a simple two-step extraction method, namely ionic liquid DLLME
combined with magnetic SPME was developed. The magnetic Citrate-Fe3O4 (Cit-Fe3O4) nanocomposite
was synthesized and can be easily separated by a powerful magnet. In addition, this technique does not
require clean-up steps and the magnetic sorbent material (i.e. after extraction, IL adsorbed onto the
magnetic material) can often be easily regenerated and reused. This new extraction methodology offers
various features such as sensitivity, cost-effective, easy to operate, short extraction time, low detection
limit, and use less-toxic organic solvents. In fact, the preconcentration method was successfully applied
for Co determination in water samples, with good accuracy and good reproducibility. The calibration
graph of two-step microextraction method was linear in the range of 0.1-250 µg/L and the percent recovery
of Co was in the range of 95-102%. This is an applicable method for cobalt trace assay in various
types of matrices in order to diminish its hazardous effects on ecosystem and environment.