Fig. 2. Single value control chart of acetaldehyde versus times. A, HS (21 psi)/GC
(16 psi); B, HS (25 psi)/GC (16 psi). HS (25 psi) and (21 psi) represented the pressure
of the injector in HS was 25 psi and 21 psi, respectively; GC (16 psi) represented
that the pressure of the capillary column inlet in GC was 16 psi. 1 psi = 6.895 kPa.