Liquid chromatography method

A method of operating liquid chromatography apparatus including a first liquid pump having a first pumping chamber, a first inlet valve for passing liquid into said first pumping chamber, a first outlet valve for discharging liquid from said first pumping chamber, a first piston for drawing liquid through said first inlet valve during a backstroke and discharging liquid through said first outlet valve during a forward stroke, and a first pressure sensor for sensing the pressure in the first pumping chamber;

• a second liquid pump having a second pumping chamber, a second inlet valve for passing liquid into said second pumping chamber, a second outlet valve for discharging liquid from said second pumping chamber, a second piston for drawing liquid through said second inlet valve during a backstroke and discharging liquid through said second outlet valve during a forward stroke;
• the method comprising the steps of:
• stopping said first piston in a mid-portion of said forward stroke;
• monitoring the pressure in said first pumping chamber with said first piston stopped in said mid-portion of said forward stroke;
• and
• controlling the operation of said first and second pumps in response to said monitoring step.

A method of operating liquid chromatography apparatus including a liquid pump having a pumping chamber, an inlet valve for receiving liquid, an outlet valve for discharging liquid to a separation column, a piston for drawing liquid through said inlet valve during a backstroke and discharging liquid through said outlet valve during a forward stroke, and a pressure sensor for sensing the pressure in the pumping chamber;

• the method comprising the steps of:
• monitoring with said pressure sensor the pressure in said pumping chamber during said forward stroke of said piston to detect the presence of air in said pumping chamber;
• determining the deficiency in liquid flow produced by said pump because of said detected air in said pumping chamber;
• and
• adjusting the operation of said pump to compensate for said deficiency.

A method of operating liquid chromatography apparatus including a first liquid pump having a first pumping chamber, a first inlet valve for passing liquid into said first pumping chamber, a first outlet valve for discharging liquid from said first pumping chamber to a separation system, a first piston for drawing liquid through said first inlet valve during a backstroke of said first piston and discharging liquid through said first outlet valve during a forward stroke thereof, and a first pressure sensor for sensing the pressure in the first pumping chamber and a first motor coupled to said first piston;

• and a second liquid pump having a second pumping chamber, a second inlet valve for passing liquid into said second pumping chamber, a second outlet valve for discharging liquid from said second pumping chamber to said separation system, a second piston for drawing liquid through said second inlet valve during a backstroke of the second piston and discharging liquid through said second outlet valve during a forward stroke thereof;
• a second motor coupled to said second piston, and a second pressure sensor for sensing the pressure in said second pumping chamber;
• the method comprising the steps of:
• monitoring with said pressure sensor the pressure in said first pumping chamber to detect an end of said forward stroke by said first piston;
• initiating said forward stroke of said second piston in response to said monitoring step;
• sensing with said second pressure sensor the pressure in said second pumping chamber to detect an end of said forward stroke by said second piston;
• and
• initiating said forward stroke of said first piston in response to said sensing step.