I am running an lcms SIM for etg in H20 (5mM Ammonium Acetate) and MeOH/ACN (1:1). after the ETG comes off I ramp up the flowrate and run 100% h2o phase, but it takes about a minutes and half of this to fully remove residual ETG from the column (biphenyl column). If I run a high conc ETG sample followed by a blank, without such an agressive flush, I get resisidual ETG in the blank sample.

Can you provide any suggestions to help flush out the ETG faster? The goal is to shorten the method as much as possible. Maybe suggest a different stationary phase or bring in an even more polar solvent (nitromethane?) to flush the column? Any experience with this problem with this compound?