Single-walled carbon nanohorn (SWCNH) was developed as new adsorbent for solid-phase extraction
using 4-nitrophenol as representative. The unique exoteric structures and high surface area of SWCNH
allow extracting a large amount of 4-nitrophenol over a short time. Highly sensitive determination of
4-nitrophenol was achieved by linear sweep voltammetry after only 120 s extraction.