Problem with column Acquity UPLC BEH
We have troubles with our columns’ lifetime (Acquity UPLC BEH C18 1.7 µm 2.1x150mm).The mobile phase is a 25 mM phosphate buffer at pH 3,6 with acetonitrile (85/15). During the run, a gradient go up to 75% acetonitrile and 25% mobile phase (NaH2PO4/ACN 85/15). Column manager is at a temperature of 30 °C. We use a VanGard precolumn.The column is cleaned every day for 500 min with water, then 10 min water/acetonitrile (50/50), and then 10 min acetonitrile.Before each using, the column is rinsed with water before it is equilibrated with mobile phase.We used two columns Acquity UPLC BEH C18 1.7 µm 2.1x150mm; one had about 300 injections, and the other reached 550 injections. For both of them, the problem is the same: peaks become deformed, with shoulders or splitting.We changed column and pre-column frits; we washed the column with water, water/acetonitrile 50/50, and 100% acetonitrile, upside down, without result. The cleaning sequence with water, methanol and THF did not improve the chromatography.What can we do to have longer lifetimes? Can we save our columns, or are they dead?