Carbon nanotubes (CNTs) are cylindrical allotrope nanostructures of carbon with unique structures and unusual properties.
The adsorption capacity of CNTs — along with their thermal and chemical stability — make them suitable candidates for new
stationary phases, pseudostationary phases, and also for sorbents in solid-phase extraction (SPE) and solid-phase microextraction
(SPME). This article outlines the latest applications for CNTs in chromatography and sample preparation.
Carbon nanotubes (CNTs) were officially discovered in 1991 by Sumio Iijima when an arc discharge method, previously used for
fullerene synthesis, formed needle-like structures on the negative electrode (1). Microscopy studies revealed concentric tubes
formed by two to 50 graphene sheets and these structures were named multi-walled carbon nanotubes (MWCNTs). A few years later,
researchers discovered that on the addition of iron (Fe) or cobalt (Co) to one of the electrodes single graphite tubes known
as single-walled carbon nanotubes (SWCNTs) were formed (2,3).
The controlled and specific synthesis of SWCNTs and MWCNTs in relatively high amounts is possible by techniques such as arc-discharge
(4), laser ablation (5), or chemical vapor deposition (CVD) (6). These processes are, in general, difficult and expensive
even before taking purification into account. Cost-effective methods to produce CNTs in larger volumes are still required.
However, the unique properties of CNTs make them potentially very useful in practice. The tensile strength and elastic modulus
of CNTs makes them the strongest and hardest materials known because of the sp2 covalent bonds between carbon atoms. But these two properties are only part of their appeal. In general, they show other
unique physical, chemical, thermal, and mechanical properties that make them useful for an extensive range of applications,
primarily in electronics and electrochemistry. However, they are also used in other fields including gene therapy, drug delivery,
neuroengineering, biosensor technology, and biomedical and tissue engineering. As a result, CNTs are probably one of the most
intensively studied nanostructured materials (7).
CNTs are also playing a significant role in analytical chemistry (Figure 1). This short review attempts to summarize the most
important applications relevant to chromatographers.
Figure 1: Principal applications of CNTs in analytical chemistry.