Diamonds show potential as column packing for high-performance liquid chromatography.

Pavel Nesterenko and colleagues at Lomonosov Moscow State University, Russian Federation, have achieved efficient separations of mixtures of aromatic hydrocarbons using nano-sized diamonds as the stationary phase in high-performance liquid chromatography (HPLC).

An ongoing challenge in chromatography has been to improve the properties of the column packings to get better separation efficiency and selectivity. Many different materials have been tested as stationary phases but only a few fulfil both the mechanical and chemical stability requirements.

Diamonds are an ideal choice of material for column packings because they offer excellent stability, so they can be used at high temperatures and pressures in the presence of strong alkalis, acids, and organic solvents. 'However, natural diamonds are too expensive and synthetic nanodiamonds, although they are cheap, have too fine particles to be of use,' explained Nesterenko.

To solve the problems of cost and particle size, Nesterenko developed a sintering technology that enabled him to obtain nanodiamonds suitable for HPLC applications. He prepared polycrystalline porous diamond particles of micron size by sintering nanodiamonds at high pressures, up to 12,000 MPa, and temperatures of 1200ºC.

Commenting on the sintered nanodiamonds, Paul Haddad of the Australian Centre for Research on Separation Science in Tasmania said 'These are an interesting new class of stationary phase because they show specific analyte interactions yet retain many important diamond properties, such as pH tolerance.'

Haddad predicts that the challenge with these materials will be to find ways to control the synthesis of suitable particles so that the chromatographic efficiency can be improved to levels similar to conventional packings, such as silica.

Janet Crombie