The present work demonstrates the application
of modified multiwall carbon nanotubes (MMWCNTs) as a
new selective and stable solid sorbent for the preconcentration
of trace amounts of Cd(II) and Pb(II) ions in aqueous
solutions. Multiwall carbon nanotubes are oxidized with
concentrated HNO3 and modified with cyanuric-SH. Cd(II)
and Pb(II) ions are quantitatively retained by the modified
multiwall carbon nanotubes. The adsorbed ions are
then eluted from the modified MWCNTs with 3.0 mL of
0.050 mol L−1 HNO3 solution and flame atomic absorption
spectrometry (FAAS) is used to measure the eluted Cd(II)
and Pb(II) ions. The linear range for the determination of
Cd(II) is maintained between 0.3 and 2,000 ng mL−1, while
for Pb(II) it remains within 1.0–2,000 ng mL−1 (in initial
solution) with detection limits of 0.1 ng mL−1 Cd(II) and
0.3 ng mL−1 Pb(II) in the initial solutions. The enrichment
factor of the modified solid phase is determined as
660 for Cd(II) and Pb(II) ions. The sorption capacity of
the modified MWCNTs for Cd(II) and Pb(II) are 11.2 and
18.6 mg g−1, respectively. The relative standard deviations
for separation and measurement of the ions in ten 100-mL
solutions containing 50 ng mL−1 Cd(II) and Pb(II) and
in 500-mL solutions containing 5.0 ng mL−1 Cd(II) and
Pb(II) were 4.2 and 4.5 % for Cd(II) and 3.4 and 3.5 % for
Pb(II), respectively. Finally, the proposed method will be
employed for the separation and determination of Cd(II) and Pb(II) in different real samples to confirm its accuracy
and validity.