Apparatus and method for liquid chromatography
First Claim
1. A method of rapidly bringing a chromatographic column through a transitory period from starting to equilibrium pressure comprising the steps of:
- setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow;
measuring the pressure of the fluid;
measuring the rate of flow of the fluid;
determining the difference between the equilibrium pressure and the measured pressure to obtain a pressure error;
increasing the rate of flow from the pumping system under the control of at least a function of said pressure error and measured rate of flow until the equilibrium value of pressure is reached;
reducing said rate of flow from the pumping system to said predetermined rate of flow;
the step of increasing the rate of flow until said estimated equilibrium value of pressure is reached including the step of controlling the rate of flow with a feedback signal that causes the pumping speed to increase substantially proportionally to the change in the difference between the set pressure and the measured pressure substantially independently of the rate of flow wherein the feedback signal is formed from the pressure error and a function that increases at a decreasing rate as the rate of flow increases.
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Abstract
To stabilize flow rate in a single-stroke, syringe-type high pressure pump at a constant value after turn-on, a control system increases the pump speed until equilibrium conditions are reached and then pumps at the present rate. In one embodiment, the system is operated in a constant pressure mode under the control of a feedback system to a point at which the pressure is estimated to provide the desired flow rate, with feedback being provided from a pressure measurement and from a flow rate measurement. The feedback from the flow measurement is increased logarithmically with the rate of pumping prior to being compared with the pressure error signal and the comparison between the previous error signal and the logarithmic flow rate signal is used to control the speed of pumping.
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Citations
51 Claims
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1. A method of rapidly bringing a chromatographic column through a transitory period from starting to equilibrium pressure comprising the steps of:
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setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; measuring the pressure of the fluid; measuring the rate of flow of the fluid; determining the difference between the equilibrium pressure and the measured pressure to obtain a pressure error; increasing the rate of flow from the pumping system under the control of at least a function of said pressure error and measured rate of flow until the equilibrium value of pressure is reached; reducing said rate of flow from the pumping system to said predetermined rate of flow; the step of increasing the rate of flow until said estimated equilibrium value of pressure is reached including the step of controlling the rate of flow with a feedback signal that causes the pumping speed to increase substantially proportionally to the change in the difference between the set pressure and the measured pressure substantially independently of the rate of flow wherein the feedback signal is formed from the pressure error and a function that increases at a decreasing rate as the rate of flow increases. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. Apparatus for rapidly bringing a chromatographic means to equilibrium pressure comprising:
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pumping system means; feedback signal means for controlling said pumping system means; means for setting a pressure for fluid from the pumping system; means for measuring the pressure of said fluid, being transferred from the pumping system means to the chromatographic means; means for measuring the rate of flow of fluid from the pumping system means and generating a flow rate signal; means for finding the difference between the set pressure and the measured pressure and generating a pressure error signal therefrom; and said feedback signal means including means for controlling the flow rate with a feedback signal formed from the pressure error signal and a function that increases at a decreasing rate as the pumping speed increases to cause the pumping speed to increase substantially proportionally to the pressure error signal substantially independently of the rate of flow. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. Apparatus comprising:
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pumping system means; feedback signal means for controlling said pumping system means; means for setting a pressure for fluid from the pumping system; means for measuring the pressure of said fluid being transferred from the pumping system means to a chromatographic means; means for measuring the rate of flow of fluid from the pumping system means and generating a flow rate signal; means for finding the difference between the set pressure and the measured pressure and generating a pressure error signal therefrom; and said feedback signal means including means for controlling the flow rate with a feedback signal formed from the pressure error signal and a function that increases at a decreasing rate as the pumping speed increases to cause the pumping speed to increase substantially proportionally to the pressure error signal substantially independently of the rate of flow. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
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48. A method comprising the steps of:
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setting a pumping speed for pumping fluid from a pumping system into a chromatographic column at a predetermined rate of flow; measuring the pressure of the fluid; measuring the rate of flow of the fluid; determining the difference between the equilibrium pressure and the measured pressure to obtain a pressure error; increasing the rate of flow from the pumping system under the control of at least a function of said pressure error and measured rate of flow until the equilibrium value of pressure is reached; reducing said rate of flow from the pumping system to said predetermined rate of flow; the step of increasing the rate of flow until said equilibrium value of pressure is reached including the step of controlling the rate of flow with a feedback a feedback signal that causes the pumping speed to increase substantially proportionally to the change in the difference between the set pressure and the measured pressure substantially independently of the rate of flow wherein the feedback signal is formed from the pressure error and a function that increases at a decreasing rate as the rate of flow increases. - View Dependent Claims (49, 50, 51)
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Specification