How does ZB-guardian/ Z-guard enhance the peak shape in an on column injection?

In an on column injection, the analytes and the sample are introduced as a liquid in the head of the column. Introducing a liquid directly to the head of the analytical column would show increased solvent interference and distorted peak shape for initial peaks.

As the oven program begins, the solvent vapor starts to move through ZB guardian/Z-guard, analytical column and reaches the detector. In the mean time, the analyte travels the ZB guardian/Z-guard and focuses as a sharp band on the head of the analytical column. Since the analytes are focused as sharp band in the analytical column head, much sharper peaks are observed. Thus the ZB guardian/Z-guard acts as a retention gap in an on column injection and separates analytes peak well from the solvent.