Colloidal crystals enter period of trial separation

Colloidal crystals made of self-assembling silica particles are highly effective at separating a variety of different compounds on a very small scale, report US chemists. The particles use separation mechanisms associated with both electrophoresis and chromatography.

’We decided to investigate the separation ability of the colloidal crystals because they are composed of pure silica, which has been the most successful substrate for high performance separations,’ said lead researcher Mary Wirth from the University of Arizona, Tucson. 

Wirth’s team synthesised a 20?m-thick crystal made of 200nm-diameter silica particles, and covered it with a polymer sheet. They inserted three dye molecules into the silica crystal through holes in the sheet, and applied an electric current. They then conducted the same experiment with three peptides. 

The crystal separated the dye molecules and peptides within only a few seconds. The researchers found that the dye molecules were mainly separated as a result of different rates of adsorption onto the silica crystal. The peptides were separated based on their different rates of electrically-driven migration through the crystal.

Wirth’s team showed that the separation ability of the crystal was superior to that of high performance liquid chromatography, and the researchers are now testing its potential for separating more complex mixtures of peptides and proteins.

Shaorong Liu, an analytical chemist from Texas Tech University, Lubbock, says that exploring some of the implications of this work could lead to new separation principles and techniques ’that will have significant impact on chemical separations’.

Jon Evans

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