Self-Assembled Nanomaterials for Enhanced Chemical Separations

May 01, 2011

This installment focuses on advanced analytical separations that incorporate nanomaterials for improved chemical selection. These new nanomaterials are based on bioinspired and polymeric self-assembled aggregates. Capillary electrophoresis and chromatographic methods were harnessed for the separation of a wide variety of samples. Compelling applications include rapid separations of 100 DNA fragments and separations of enantiomers, aptamers, small molecules, and glycans. The implementation, performance, and fundamental properties of these new media are discussed.

The Pittsburgh Conference of Analytical Chemistry and Applied Spectroscopy (Pittcon), was held March 12–18, 2011, at the World Congress Center in Atlanta, Georgia. The Pittcon 2011 technical program boasted a number of exciting advances in analytical chemistry, including a number of leading edge technologies in the area of separation science. A session sponsored by the American Chemical Society's (ACS) Subdivision of Chromatography and Separations Chemistry on self-assembled nanomaterials for enhanced chemical separations was organized by Professor Lisa Holland of the Department of Chemistry, West Virginia University (Morgantown, West Virginia).

Presentations in this Pittcon session outlined enhanced separations and diverse applications with techniques based on new materials for thin-layer chromatography (TLC), solid-phase microextraction (SPME), and capillary electrophoresis (CE). Some separation media discussed in this session emanated from fabrication techniques such as photolithography and chemical vapor deposition. A new "spin" on fabrication was nanofiber electrospinning. Self-assembly of biomolecules inspired by natural systems was a prominent theme. Generally, these biological selectors were effective for the separation of biopolymers such as DNA, aptamers, and glycans, as well as biologically relevant small molecules. Classical self-assembled surfactant micelles were adapted to improve electrically driven separations.

The purpose of this installment of "Column Watch" is to summarize some of the key techniques presented in this session and discuss future directions that new self-assembled nanomaterials may take in separation science.

Background in Self-Assembled Nanomaterials for Separation Science

Traditional separation media such as chromatographic packing material or open-tubular chromatography columns are fabricated through the covalent modification of a polymeric or inorganic (silica, for example) surface. With new advances in material science, newer strategies arise that result in sophisticated architecture for chemical separations based on molecular self-assembly. These processes result from spontaneous molecular interactions to control the size, shape, or surface characteristics of the assembly, often resulting in what is a highly ordered and unique structure. A benefit of this approach is that reduced chemical modification results in a greatly simplified fabrication protocol of what is a complex final product. Assembled structures may be made from components that are inorganic or organic (or both) or biological in nature. Frequently, such materials originate from or are inspired by biological systems, such as cellular membranes. The resulting supramolecular assembly can occur through a variety of mechanisms such as ionic, hydrophobic, or hydrophilic interactions, as well as adsorption. Although individual interactions may be weak, the summative force from these interactions stabilizes the entire assembly. These molecular assemblies may possess nanoscale features as well as unique properties that macroscale materials often lack.