However, it is easy to diagnose if your ghost peak is from the mobile phase. Simply run a blank gradient. It’s better if you can do this without performing an injection (to rule out the injection as the source of the ghost peak). In Empower, it is called ‘condition column’. If the peak is coming from the mobile phase then increasing the equilibration time at the beginning of the gradient will increase the size of the peak. For example, you could compare holding at the starting conditions for 5 minutes to holding at 10 minutes. The ghost peak will double in size if it is coming from the mobile phase.