Magnetic Multi-Walled Carbon Nanotubes Modified with Polythiophene as a Sorbent for Simultaneous Solid Phase Microextraction of Lead and Cadmium from Water and Food Samples

Polythiophene (PT) coated magnetic multi-walled carbon nanotubes (MMWCNTs) as a magnetic sorbent was synthesized and characterized by FT-IR, SEM, XRD, and VSM. The sorbent was applied for simultaneous solid-phase microextraction of trace amounts of lead and cadmium ions from various matrices. The retained analytes were eluted using nitric acid solution (0.5 mol L-1) and quantified by flame atomic absorption spectrometry. The main factors affecting the extraction of lead and cadmium such as pH, type and concentration of eluent, amount of the sorbent, ionic strength and sample volume were investigated and optimized. Under the optimized conditions, the detection limits (based on 3Sb/m) of 0.54 and 0.03 µg L-1 and the enhancement factors of 197.6 and 195.5 were obtained for lead and cadmium, respectively. The relative standard deviations of 1.5% (n = 6) at 50.0 µg L-1 of lead and 2.1% at 5.0 µg L-1 of cadmium were achieved. The method was found to be effective, selective, rapid, and simple for the determination of trace amounts of lead and cadmium and was successfully applied to the determination of lead and cadmium in water, black tea, rice, and milk samples without evident interference from the complex matrix. Furthermore, the sorbent showed high capacity, and the precision and accuracy of the method were satisfactory. The validity of the method was examined through the recovery experiments and independent analysis by electrothermal atomic absorption spectrometry.