Study on the performance of micro-flow injection preconcentration method on-line coupled to thermospray flame furnace AAS using MWCNTs wrapped with polyvinylpyridine nanocomposites as adsorbent

This work describes the synthesis and characterization of a new adsorbent nanocomposite based on multiwalled carbon nanotubes (MWCNTs) and polyvinylpyridine and its use in the development of a highly sensitive micro-flow injection preconcentration method coupled to TS-FF-AAS for the determination of very low levels of Cd. The characterization of the nanocomposite was performed by FT-IR, TGA, SEM, TEM and textural data measurements using the BET and BJH methods. The optimized conditions of the micro-flow injection preconcentration method involved a preconcentrated sample (8.8 mL) at pH 8.0 flowed through 50.0 mg of nanocomposite packed into a mini-column at a flow rate of 4.4 mL min(-1). The on-line elution of Cd(II) ions towards the TS-FF-AAS detector was carried out in countercurrent at a flow rate of 0.6 mL min(-1) using 1.0 mol L-1 HCl. The analytical curve ranged from 0.12 to 6.0 mg L-1 (r = 0.997), and an enhancement factor of 19.5, sample throughput of 15 h(-1) and consumptive index of 0.45 mL were achieved. In terms of sensitivity, the uniquely high adsorption capacity of the nanocomposite was confirmed by the low limit of detection (36 ng L-1) achieved after implementing the preconcentration step in TS-FF-AAS. In terms of selectivity, the proposed method was shown to be tolerable to several foreign ions and applicable to different kinds of waters (tap, mineral, lake, and synthetic seawater), cigarettes, a food sample (powder chocolate), a medicinal herb (Ginkgo biloba) and a certified reference material (fish protein DORM-3).