The application of silica monolith for solid phase extraction

Abstract

Silica monolith had been in existence for more than a decade and the application of silica monolith for separation is well established. The monolith has been fabricated for separation in the form of columns. In a monolithic column, monolith represents a continuous single rod of porous material. It is characterized by high permeability due to uniform distribution of macropores and mesopores throughout the network enabling separation of many analytes. The macropores present provide the permeability for solvents to flow through, whereas mesopores provide the high surface area for separation. As the formed network fills the column volume completely, inter-particulate voids are absent, resulting in 100% flow of mobile phase through the column. Although monolith has been explored for other applications in analysis, surprisingly the application of unmodified silica monolith for solid phase extraction has never been thoroughly investigated. In this thesis, the feasibility of applying silica monolith for solid phase extraction has been demonstrated in examples of extracting various hydrophilic analytes such as catecholamines, metanephrine, opiates, cocaine and ketamine from urine. Furthermore, the developed silica monolithic cartridge was tested for desalination purpose. Attempts have also been made to enhance the surface properties of the silica monolith. The findings in this thesis could shed some light on the potentials of applying silica monolith as a tool for solid phase extraction. In this thesis, only the inorganic silica monolith was investigated. There are many other organic or inorganic-organic hybrid monoliths existing or under development. These monoliths could be matrices suitable for solid phase extraction of analytes of different physicochemical properties.