I determine biodiesel produced from vegetable oils (triglycerides) by TLC method. I use a solvents system comprising of Petroleum ether:Diethyl ether:Acetic acid in the ratio of 80:30:1. The biodiesel (FAME) comes on the top i.e. near the solvent front. Just below the biodiesel there is a spot of leftover triglycerides, which is very close to the FAME spot. I want a sufficient gap between the spots of FAME and triglycerides. Please suggest a solvent system for that.