Ultrasound-assisted solid-phase extraction using multiwalled carbon nanotubes for determination of cadmium by flame atomic absorption spectrometry

Ultrasound-assisted solid-phase extraction (SPE) with multiwalled carbon nanotubes (MWCNTs) as a solid sorbent and 1-(2-pyridylazo)-2-naphthol (PAN) as a chelating agent was developed for the determination of trace and ultratrace amounts of Cd(II) ions in aqueous samples. The solution containing Cd(II) complexed with PAN was passed through the syringe filter with a PVDF membrane loaded with 25 mg of MWCNTs. The elution process was performed with 2.0 mL of 2.0 mol L-1 HNO3 with assistance of sonication. In order to obtain the high recovery of the Cd(II) ions, the proposed procedure was optimized for various analytical parameters such as pH, amounts of PAN, sample volume, and elution conditions such as volume and concentration of eluent and influence of sonication and temperature. The investigation shows that sonication considerably improves the recovery, whereas temperature does not influence the elution process. Under optimized conditions Cd(II) ions can be determined with very good recovery (99 +/- 3%), precision (RSD = 3.2%) and detection limit (0.3 ng mL(-1)) for an enrichment factor of 50. The effect of common coexisting ions was also investigated. Cd(II) can be determined in the presence of heavy metal ions and alkali metals. The proposed ultrasound-assisted SPE was applied for the determination of Cd(II) in water samples and biological samples (Lobster Hepatopancreas).