Effect of carbon nanotube functionalization in micro-solid-phase extraction (μ-SPE) integrated into the needle of a syringe

In this paper, we report the implementation of polar and nonpolar functionalized multiwalled carbon nanotubes (MWCNTs) as sorbent in μ-SPE integrated into the needle of a syringe. Excellent preconcentration of diverse pharmaceutical analytes was possible without the need for specific pH adjustments using just 300 μg of functionalized nanotubes. Enrichment factors were as high as 6.4, extraction efficiencies were as high as 25.6%, and detection limits as low as 0.08 ng/ml were obtained. The sorption on nanotubes followed Freundlich isotherms, and it was seen that polar analytes adsorbed more strongly on carboxylated MWCNTs, while amphoteric, relatively less polar and basic analytes had greater affinity for MWCNT and those with octadecylamine functionalization.