To remove the solid debris almost immediately after it has been deposited, this newly installed filter was back-flushed by diverting the flow of the mobile phase from the column (350 bar) to the filter (20 bar) using a T-connector (Valco part ZT1C) (Figure ). This simple technique of diverting the flow through a low pressure filter line taking advantage of the high back pressure of the column by adding a T-connector between these two lines has not to the best of our knowledge been previously reported. The automated back-flushing of the filter continues for approximately one minute after each injection thus preventing both debris build-up and sample carry over.