Multi-walled carbon nanotubes as sorbent for flow injection on-line microcolumn preconcentration coupled with flame atomic absorption spectrometry for determination of cadmium and copper

Multi-walled carbon nanotubes (MWNTs) were used as sorbent for flow injection (FI) on-line microcolumn preconcentration coupled with flame atomic absorption spectrometry (FAAS) for determination of trace cadmium and copper in environmental and biological samples. Effective preconcentration of trace cadmium and copper was achieved in a pH range of 4.5-6.5 and 5.0-7.5, respectively. The retained cadmium and copper were efficiently eluted with 0.5 mol L-1 HCl for online FAAS determination. The MWNTs packed microcolumn exhibited fairly fast kinetics for the adsorption of cadmium and copper, permitting the use of high sample flow rates up to at least 7.8mL min(-1) for the FI on-line microcolumn preconcentration system without loss of the retention efficiency. With a preconcentration time of 60 sec at a sample loading flow rate of 4.3 mL min(-1), the enhancement factor was 24 for cadmium and 25 for copper at a sample throughput of 45 h(-1). The detection limits (3 sigma) were 0.30 and 0.11 mgL(-1) for Cd and Cu, respectively. The precision ( RSD) for 11 replicate measurements was 2.1% at the 10-mgL(-1) Cd level and 2.4% at the 10-mgL(-1) Cu level. The developed method was successfully applied to the determination of trace Cd and Cu in a variety of environmental and biological samples.