I am currently routine using a C18 method with LCMS Ion Trap (ESI) to screen for my sample. The mobile phase is gradient . Mobile phase 1 is 0.1% TFA in water . The gradient is from 99% to 30% in 30minutes. I need to develop a column test mix containing void marker, neutral probe , acidic probe and basic probe. The Mw of my compounds range from 90 to 250. Please advice on the type of compounds which l can use

Thanks and Regards
Drew