A solution (15 mL) containing sample or standards of cadmium
and lead ions and DT (3 mg L1
) at pH of 7.0 was poured into a
glass screw-cap conical-bottom centrifuge tube. Then 0.5 mL of
methanol solution (as disperser solvent) containing benzophenone
(0.02% (w/v)) (as sorbent) was rapidly injected into a sample solution
by using 1.0 mL syringe. A cloudy solution formed in the test
tube (the cloudy state was stable for a long time). This cloudy state
resulted from the dispersion of fine particles of benzophenone in
the bulk aqueous sample. Then, the mixture was centrifuged at
4500 rpm for 3 min. Accordingly, after centrifuge, the dispersed
fine particles of benzophenone were sedimented in the bottom of
the conical test tube. The aqueous phase was then separated completely
by a syringe. Later, the sedimented phase was dissolved and
made up to 1.0 mL by adding ethanol. The resultant solution was
introduced into the flame by conventional aspiration. The scheme
for extraction and determination steps is illustrated .