2.3. Procedure
2.3.1. Column method
Hundred milligrams of DPC-SBA-15 was packed in a glass column
with dimensions 120 mm in length and 20 mm in diameter,
and blocked by two polypropylene filters at the ends to prevent
loss of the nanoporous material during sample loading. Prior to
extraction, the column was preconditioned successively with 5 mL
absolute ethanol, 5 mL toluene, and 5 mL absolute ethanol and then
washed with double-distilled water until it became free of organic
solvent. A 25 mL of standard solution containing 1 mg L−1 cadmium
and copper ions, after adjusting the pH of sample to 6.0 by adding
HNO3 or NaOH solution, was passed through the column at a flow
rate of 10 mL min−1 using a peristaltic pump. The sorbed cadmium
and copper ions were eluted from the column with HCl (2 mol L−1)
at a flow rate of 2 mL min−1. Afterwards, the analytes in the eluent
were determined by FAAS.