To prevent column plugging, it is reasonable to filter the samples and the eluent through a filter with 2 µm pore size before usage. Furthermore the compatibility of the mobile phase is an important factor. Standard RP phases are stable within a pH range 2-8. Under certain conditions (presence of buffers) the stationary phases are even chemically stable until pH 12. When using buffered mobile phases it is necessary to flush the silica-based column with pure solvents to avoid precipitation of buffer salt. As prophylaxis KNAUER offers a universal UHPLC precolumn filter with 0.5 µm pore size.