Apparatus for liquid chromatography
First Claim
1. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
- means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow;
means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid;
means for estimating the equilibrium value of pressure from said measurements of said characteristic made at said low value of pressure;
means for increasing the pumping rate of flow until said estimated equilibrium value of pressure is reached; and
said means for estimating including means for taking the time derivative of the pressure;
means for measuring the pressure at a predetermined fraction of the difference between the maximum time derivative of the pressure and zero; and
means for multiplying the pressure at that point by a factor which is the reciprocal of the predetermined fraction; and
reducing said rate of flow from the pumping system to said predetermined rate of flow.
1 Assignment
0 Petitions
Accused Products
Abstract
To stabilize flow rate in a single-stroke, syringe-type high pressure pump to a constant value after turn-on, a control system increases the pump speed until equilibrium conditions are reached and then pumps at the preset rate. In one embodiment, the control system senses the maximum rate of change of pressure, detects a pressure when the rate of change is two-thirds of the maximum, increases the pump rate until the pressure is three times that at the value of the detected pressure and begins pumping at the preset constant flow rate. In other embodiments: (1) a pumping system is operated at a flow rate ten times the preset flow rate and, when the time derivative of the pressure has dropped to nine tenths of its maximum, the pump motor speed is reduced to the preset flow rate; (2) the outflow of the column is measured under no load conditions at the desired flow rate and when a column is connected, the pumping speed is increased until the same outflow results before reducing the pumping rate; and (3) the system is operated in a constant pressure mode to a point at which the pressure is estimated to provide the desired flow rate, the flow rate measured, and if the flow rate is not the preset one, a new pressure measurement is set and the procedure repeated.
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Citations
41 Claims
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1. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for estimating the equilibrium value of pressure from said measurements of said characteristic made at said low value of pressure; means for increasing the pumping rate of flow until said estimated equilibrium value of pressure is reached; and said means for estimating including means for taking the time derivative of the pressure;
means for measuring the pressure at a predetermined fraction of the difference between the maximum time derivative of the pressure and zero; and
means for multiplying the pressure at that point by a factor which is the reciprocal of the predetermined fraction; and
reducing said rate of flow from the pumping system to said predetermined rate of flow. - View Dependent Claims (2, 3, 4)
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5. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; said means for measuring, at a time of low value of pressure, a characteristic of fluid including means for measuring the pressure of fluid being transferred from the pumping system to the chromatographic column at a low value of pressure; said means for increasing the rate of flow includes means for estimating the equilibrium value of pressure from said characteristic; and
means for increasing the pumping rate of flow until said estimated equilibrium value of pressure is reached;said means for measuring a characteristic including the means for measuring the derivative with respect to time of the pressure of fluid being transferred from the pumping system to the chromatographic column at a low value of pressure;
said means for increasing the rate of flow including means for taking the time derivative of the pressure;
means for measuring the pressure at a predetermined fraction of the difference between the maximum time derivative of the pressure and zero; and
means for multiplying the pressure at that point by a fact which is the reciprocal of the predetermined fraction; andsaid means for reducing said rate of flow of pumping to said predetermined rate of flow including means for storing a value representing the instantaneous pressure when the pressure time derivative reaches said predetermined point;
means for comparing the stored value of instantaneous pressure with the instantaneous pressure as it changes; and
means for slowing the rate of flow when the ratio of the maximum pressure time derivative minus the instantaneous time derivative to the maximum pressure-time derivative multiplied by the instantaneous pressure value is larger than the stored pressure value. - View Dependent Claims (6, 7)
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8. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; and said means for measuring a characteristic of fluid including means for counting drops from the column and deriving a signal in analog form representing the drops; and
means for applying a correction factor to said signal so as to cause it to represent the outflow from the column. - View Dependent Claims (9, 10, 11)
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12. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; said means for measuring a characteristic of fluid including means for counting drops from the column and deriving a signal in analog form representing the drops; and
means for applying a correction factor to said signal so as to cause it to represent the outflow from the column;means for applying a correction factor includes means for converting the signal to digital form and applying a digital correction factor;
p1 saim means for increasing the rate of pumping flow includes means for increasing the rate of flow until the outflow from the chromatograph means equals the predetermined rate of flow;said means for increasing the rate of flow includes means for comparing the measured outflow with a preset outflow and generating a resulting signal; and
means for causing said resulting signal to control the rate of pumping until said measured outflow equals said preset outflow; andsaid means for increasing the rate of flow including means for applying a reference signal to the pumping system corresponding to the equilibrium rate while the chromatographic means is under no load;
means for generating a calibration factor signal by comparing the reference signal with the signal derived from the outflow measuring circuit when the chromatographic column has the desired outflow rate;
means for multiplying the calibration factor signal by the measured signal and comparing it to the desired signal during operation of the chromatographic column under load; and
means for discontinuing application of the reference signal to the motor control circuit and applying the factored measured signal when the calibrated measured signal differs from the desired signal. - View Dependent Claims (13, 14)
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15. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; and said means for measuring a characteristic of a fluid including means for measuring the pressure caused by a pump supplying fluid to the chromatographic system;
means for measuring a dynamic characteristic of the system which is inversely proportional to the pressure;
means for establishing a ratio between a point on the dynamic characteristic and its range from maximum to zero;
means for measuring the pressure at said point; and
means for calculating other points of pressure from proportionality between said dynamic characteristic and said pressure measurement. - View Dependent Claims (16, 17, 18)
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19. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; and said means for increasing the rate of flow comprises means for estimating the equilibrium pressure for a constant flow-rate chromatographic run from said measurement of a characteristic;
means for increasing the pump motor speed rapidly until said pressure is reached;
means for permitting the flow rate to stabilize at said set pressure;
means for repeating the process of estimating the pressure and increasing the speed of the pumping system to the estimated pressure until the flow rate is close to the constant flow rate; and
means for operating said chromatograph at the constant flow rate. - View Dependent Claims (20, 21)
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22. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; said means for increasing the rate of flow comprising means for estimating the equilibrium pressure for a constant flow-rate chromatographic run from said measurement of a characteristic;
means for increasing the pump motor speed rapidly until said pressure is reached;
means for permitting the flow rate to stabilize at said set pressure;
means for repeating the process of estimating the pressure and increasing the speed of the pumping system to the estimated pressure until the flow rate is close to the constant flow rate; and
means for operating said chromatograph at the constant flow rate;means for increasing the speed of the pumping system including means for comparing the pressure with the estimated pressure to derive a difference signal; and
means for applying the difference signal to a feedback loop to control the pumping system speed until the set pressure equals the estimated pressure;means for operating the chromatograph at a constant flow rate including means for applying a potential to the motor which is constant, whereby the motor drives the pump at a constant flow rate; and means for determining when the pressure is equal to the estimated pressure comprises means for determining when the slope of the pressure-time curve is approximately zero;
means for determining when the difference between the set pressure and the measured pressure is approximately zero; and
means for selecting the time when both the slope of the pressure-time curve is approximately zero and the difference between the measured pressure and set pressure is approximately zero as the end of the transitory period. - View Dependent Claims (23)
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24. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; and said means for measuring a characteristic of the fluid comprising means for deriving a signal representing the pressure of the pump;
means for taking the derivative of the signal representing the derivative of the pump;
means for establishing a set equilibrium pressure;
means for comparing the measured pressure with the equilibrium pressure; and
means for detecting when the slope of the pressure-time characteristic and the difference between measured and set pressure characteristic are both substantially zero, whereby the equilibrium time is detected.
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25. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; means for deriving a signal representing the rate of flow of said fluid as it leaves the outlet of the chromatographic column; means for detecting characteristics of an effluent in the chromatograph; means for recording the characteristics of the effluent on a chart; and means for varying the speed of the chart in direct proportion to the signal representing the rate of flow of fluid as it leaves the outlet.
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26. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for estimating the equilibrium value of pressure from said characteristic; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; and said means for measuring a characteristic includes means for measuring the derivative with respect to time of the pressure of fluid caused by the pumping system at a low value of pressure. - View Dependent Claims (27)
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28. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; said means for increasing the rate of flow including means for estimating the equilibrium value of pressure from said characteristic; and
means for increasing the pumping rate of flow until said estimated equilibrium value of pressure is reached;said means for measuring a characteristic including means for measuring the derivative with respect to time of the pressure of fluid being transferred from the pumping system to the chromatographic column at a low value of pressure; said means for increasing the rate of flow including means for taking the time derivative of the pressure;
means for measuring the pressure at a predetermined fraction of the difference between the maximum time derivative of the pressure and zero; and
means multiplying the pressure at that point by a factor which is the reciprocal of the predetermined fraction, andsaid means for reducing said rate of flow of pumping to said predetermined rate of flow including means for storing a value representing the instanteous pressure when the pressure time derivative reaches said predetermined fraction; means for comparing the stored value of instanteous pressure with the instantaneous pressure as it changes; and
means for slowing the rate of flow when the ratio of the maximum pressure time derivative minus the time derivative at the predetermined fraction to the maximum pressure time derivative multiplied by the instantaneous pressure measured as it changes becomes substantially equal to the stored pressure value. - View Dependent Claims (29, 30)
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31. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; said means for increasing the rate of flow including means for taking the time derivative of the pressure;
means for measuring the pressure at a predetermined fraction of the difference between the maximum time derivative of the pressure and zero; and
means for multiplying the pressure at that point by a factor which is the reciprocal of the predetermined fraction.
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32. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; and said means for increasing the rate of pumping flow including means for increasing the rate of flow until the outflow from the chromatograph means equals the predetermined rate of flow.
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33. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system to said predetermined rate of flow; and means for reducing said rate of flow from the pumping system to said predetermined rate of flow; said means for increasing the rate of flow including means for comparing the measured outflow with a preset outflow and generating a resulting signal; and
means for causing said resulting signal to control the rate of pumping until said measured outflow equals said preset outflow.
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34. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of a low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; and said means for increasing the rate of flow including means for applying a reference signal to the pumping system corresponding to the equilibrium rate while the chromatograph is under no load;
means for generating a calibration factor signal by comparing the reference signal with the signal derived from the outflow measuring circuit when the chromatographic column has the desired outflow rate;
means for multiplying the calibration factor signal by the measured signal and comparing it to the desired signal during operation of the chromatographic column under load; and
means for discontinuing application of the reference signal to the motor control circuit and applying the factored measured signal when the calibrated measured signal differs from the desired signal. - View Dependent Claims (35, 36)
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37. Apparatus for rapidly bringing a chromatographic column to equilibrium pressure comprising:
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means for setting a pumping speed for pumping fluid from a pumping system into said column at a predetermined rate of flow; means for measuring, at a time of low value of pressure, a characteristic of fluid being transferred from the pumping system to the chromatographic column related to the pressure of the fluid; means for increasing the rate of flow from the pumping system under the control of at least said measured characteristic until the equilibrium value of pressure is reached; means for reducing said rate of flow from the pumping system to said predetermined rate of flow; said means for measuring a characteristic of fluid including means for measuring the fluid outflow of the chromatograph; said means for increasing the rate of flow including means for applying a reference signal to the pumping system corresponding to the equilibrium rate while the chromatographic means is under no load;
means for generating a calibration factor signal by comparing the reference signal with the signal derived from the outflow measuring circuit when the chromatographic column has the desired outflow rate;
means for multiplying the calibration factor signal by the measured signal and comparing it to the desired signal during operation of the chromatographic column under load; and
means for discontinuing application of the reference signal to the motor control circuit and applying the factored measured signal when the calibrated measured signal differs from the desired signal. - View Dependent Claims (38, 39)
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40. Apparatus for operating a chromatograph comprising:
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means for applying fluid from a pumping system into a chromatographic column system; means for detecting chromatographic peaks in the effluent as the fluid passes through the chromatographic column system; means for recording said chromatographic peaks; means for measuring the rate of flow of said fluid from said chromatographic column system and generating a signal related thereto; and means for controlling the rate of recording said peaks in response to said signal so that the rate of recording is directly proportional to the rate of flow of fluid between the pumping system and the chromatographic column system. - View Dependent Claims (41)
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Specification