Silica gel is the most common stationary phase in TLC and HPTLC of herbicides but reversed-phases (silica gel modified with C8, C 18, e.g., RP-18 W, Nano-Sil C 18 -100, silica gel impregnated with paraffin oil) can also be used. Silica gel impregnated with diethylene glycol is suitable for triazine herbicides.