MONOLITHIC COLUMNS FOR SEPARATION OF LOW-MOLECULAR COMPOUNDS

Crosslinking monomers with various lengths of methylene or oxyethylene chains between two methacrylate units were applied for preparation of polymethacrylate monolithic columns suitable for isocratic separation of low-molecular compounds, using lauryl methacrylate as the functional monomer for reversed-phase chromatography. The crosslinking monomers included ethylene-, tetramethylene-, hexamethylene-, dioxyethylene-, trioxyethylene-, and tetraoxyethylene dimethacrylates. The replacement of generally used ethylene dimethacrylate as a crosslinking monomer by monomers with longer methylene and oxyethylene chain led to significant increase in the column efficiency. For example, a column prepared with tetraoxyethylene dimethacrylate shows the column efficiency of 71 000 theoretical plates per meter and offers fast isocratic separation of six low-molecular alkylbenzenes in 2 minutes. This confirms the significant effect of the length of the oxyethylene chain in the crosslinking monomer on the efficiency of polymethacrylate capillary columns.