Developments in detection methods and use of superheated water as an eluent for liquid chromatography

A system has been developed to link superheated water liquid chromatography with flame ionisation detection. The system has been demonstrated to be robust, sensitive and have a linear response, therefore having advantages over existing commercial universal detectors, such as refractive index and evaporative light scattering detectors. A wide variety of compounds, such as non-volatiles and volatiles, with and without chromophores have not only been detected by flow injection analysis, but also separations have been demonstrated. The columns used have been polystyrene divinylbenzene, various ion exchange columns, Zirconia-PBD and porous graphitic carbon, all of which have been proven to be stable at the conditions required to produce superheated water. The separation of various mixtures have required pH control and the use of buffers, all of which have been found to be compatible with the system. The results obtained from the system using sugars, amino acids and polysaccharides, which cannot traditionally detected directly by FID or UV without derivatisation, have proven that detection is linear and detection limits are better than existing universal detectors. Also it has been demonstrated that compounds which are not detected by flame ionisation detection, such as ammonia, formaldehyde, dichloromethane and ionic compounds such as sodium nitrite, can be detected by the new system.