have been applied to direct determination of heavy
metal ions. ICP-MS has some advantages such as accuracy, speed,
multi-elemental determination, wide linear range, and low determination
limits [13–15]. However, low concentrations of metal
ions and matrix interference in samples make direct determination
using ICP-MS very difficult. Therefore, the determination of very
low levels of heavy metal ions has become increasingly very
important in environmental chemistry. It is generally impossible
to determine trace metal ions in environmental samples directly
because of interfering species in the surrounding matrix, or the
concentration of the analyte being below the detection limit of
the instrument. So preconcentration and separation procedures
are necessary to improve the sensitivity in trace-metal determination.
The widely used techniques for the separation and preconcentration
of trace amounts of heavy metals from environmental
samples include cloud point extraction (CPE) [16–18], solid-phase
extraction (SPE) [19–21], solid phase microextraction (SPME) [22],
dispersive liquid-liquid microextraction (DLLME) [23,24].