LP phases are designed for use at low pH conditions and consists of two very bulky hydrophobic protective groups to prevent the siloxane bond from hydrolysis at low pH conditions. So Ultisil LP is extremely stable in very low pH mobile phases and at high temperatures, making it the most stable phase for low pH applications in the market. Because it is not endcapped and has more surface silanols, LP phase has more retention for some early eluted polar compounds, and provides different selectivities.