Carbon nanotubes as the sorbent for integrating μ-solid phase extraction within the needle of a syringe

In this research we report the implementation of micro-solid-phase extraction (μ-SPE) in the needle of a syringe for integrating sampling, analyte enrichment and sample introduction into a single device. Both single- and multi-walled carbon nanotubes (CNTs) were explored as high performance sorbents for μ-SPE in packed and self assembled formats. The need for such a sorbent was critical because the needle probe could hold only a small amount of material (around 300 μg). Conventional C-18 and self-assembled CNTs were found to be ineffective with enrichment factors less than one. However, packed beds of CNTs were found to be excellent sorbent phases, where high extraction efficiencies (as high as 27%) as well as enrichment factors (close to 7) could be achieved. The overall method showed excellent linearity, reproducibility, and low method detection limit (0.1-3 ng/mL for MWNTs). The sorption on CNTs followed Freundlich isotherms, and the functionalized CNTs were more effective for enriching the polar compounds.