Carbon dioxide based chromatography systems including multiple carbon dioxide pumps

A CO2-based chromatography system comprising:

• a first CO2 pump disposed to deliver CO2 to a chromatography column;
• a liquid modifier pump;
• a second CO2 pump located downstream of the column and disposed to operate independently of the first CO2 pump to introduce CO2 into a flow stream at an output of the column, the second CO2 pump operating in constant pressure mode in order to maintain a target pressure;
• and
• an active splitter disposed to receive a liquid modifier from the liquid modifier pump, the active splitter disposed to deliver liquid modifier to the chromatography column according to a gradient, and further disposed to introduce liquid modifier into the flow stream at the output of the column according to a reverse gradient compared to the gradient entering the chromatography column.

A CO2 based-pump system comprising:

• a CO2 pump;
• a liquid modifier pump;
• a first active splitter disposed to receive a liquid modifier from the liquid modifier pump, introduce the liquid modifier to a chromatography column according to a gradient, and introduce the liquid modifier into a flow stream downstream of the chromatography column according to a reverse gradient compared to the gradient entering the chromatography column;
• and
• a second active splitter disposed to receive CO2 from the CO2 pump, introduce CO2 to the chromatography column, and introduce CO2 into the flow stream downstream of the chromatography column to maintain a target pressure.