Carboxylated Multiwalled Carbon Nanotubes as Dispersive Solid-Phase Extraction Sorbent to Determine Eighteen Polychlorinated Biphenyls in Vegetable Samples by Gas Chromatography-Mass Spectrometry

Figure 2

Optimization of major factors affecting extraction and cleanup efficiency (): (a) extraction solvent; (b) extraction time; (c) volume of toluene; (d) amount of MWCNTs-COOH; (e) cleanup time.

(a)

(b)

(c)

(d)

(e)