4. Conclusion
A solid-phase extraction procedure based on DPC-MWCNT is very simple, fast, reproducible and selective for the determination of cadmium ions. Compared with other solid phases, DPC-MWCNT has the advantages of a high-capacity factor, a low limit of detection and a high enrichment factor. Due to the relatively high preconcentration factor, trace metal ions at ng mL−1 level in high-volume samples can be determined and separated by functionalized multiwall carbon nanotube.