2.4. Dispersive liquid–liquid microextraction procedure
A volume of 25.0mL of ultra pure water was placed in a
40mL screw-cap glass test tube with conical bottom and
spiked at the level of 50g L−1 of lead. A 2.50 of methanol
(disperser solvent), containing 52L of carbon tetrachloride
(extraction solvent) and 50L of DDTP (chelating agent), were
injected rapidly into a sample solution using a 2.50-mL syringe
(Gastight, Hamilton). A cloudy solution (resulting from the
dispersion of the fine droplets of carbon tetrachloride in the
aqueous sample) was formed in the test tube. In this step, the
lead ions react with DDTP (Fig. 2) and extract into the fine
droplets of carbon tetrachloride. The mixture was then centrifuged
at 3800 rpm for 2min. After this process, the dispersed
fine droplets of carbon tetrachloride were sedimented at the
bottom of the conical test tube (25 ± lL).
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