Pumpless system for gradient buffer production

A pumpless method for gradient elution, comprising:

• providing two or more flowpaths connected at a mixing point;
• for each of the two or more flowpaths, flowing a liquid component down the flowpath by:
• pressurizing the liquid component;
• metering a flow rate of the liquid component using a closed-loop flow control apparatus including a dome-loaded diaphragm valve, a flow transducer, and an electronic flow controller operably coupled to the flow transducer and the dome-loaded diaphragm valve;
• combining the liquid components at the mixing point to form a mixture;
• using a sensor to evaluate a composition of the mixture;
• and
• using an electronic master controller, receiving input from the sensor and independently controlling the closed-loop flow control apparatus of each of the two or more flowpaths so as to vary the composition of the mixture over time.