Retention time stability in a gas chromatographic apparatus
First Claim
1. A method for performing a chromatographic analysis of a fluid in a separation column having an outlet subject to a barometric pressure patm, comprising the steps of:
- providing fluid flow of the fluid in the separation column;
sensing a plurality of actual operating condition parameters to which the fluid flow is subjected, the plurality including the barometric pressure patm ;
providing information representative of a desired operating condition parameter;
determining a desired average linear velocity of the fluid flow according to the desired operating system parameter;
determining an actual average linear velocity of the fluid flow according to the sensed plurality of actual operating condition parameters; and
controlling, as a function of a predetermined relationship of the desired average linear velocity to the actual average linear velocity, the amount of fluid flow to cause the actual average linear velocity to substantially equal the desired average linear velocity.
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Accused Products
Abstract
The effect of barometric pressure variation on the retention time stability of a chromatographic analytical system is compensated by active control of the amount of fluid flow by way of a fluid flow controller, preferably in the form of an electronic pressure control system. Control signals are derived by: receiving data representative of a desired operating condition parameter, such as column inlet pressure; sensing actual operating condition parameters such as inlet pressure pi and barometric pressure patm ; determining a desired average linear velocity of the fluid flow according to the desired operating system parameter; determining an actual average linear velocity of the fluid flow according to the sensed plurality of actual operating condition parameters; and controlling, as a function of a predetermined relationship of the desired average linear velocity to the actual average linear velocity, the amount of fluid flow to cause the actual average linear velocity to substantially equal the desired average linear velocity.
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Citations
29 Claims
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1. A method for performing a chromatographic analysis of a fluid in a separation column having an outlet subject to a barometric pressure patm, comprising the steps of:
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providing fluid flow of the fluid in the separation column; sensing a plurality of actual operating condition parameters to which the fluid flow is subjected, the plurality including the barometric pressure patm ; providing information representative of a desired operating condition parameter; determining a desired average linear velocity of the fluid flow according to the desired operating system parameter; determining an actual average linear velocity of the fluid flow according to the sensed plurality of actual operating condition parameters; and controlling, as a function of a predetermined relationship of the desired average linear velocity to the actual average linear velocity, the amount of fluid flow to cause the actual average linear velocity to substantially equal the desired average linear velocity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Apparatus for performing a chromatographic analysis of a fluid in a separation column having an outlet subject to a barometric pressure patm, comprising:
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fluid flow controller for providing a selectable flow of the fluid in the separation column; a plurality of transducers for sensing a respective plurality of actual operating condition parameters to which the fluid flow is subjected, the plurality including the barometric pressure patm ; means for providing information representative of a desired operating condition parameter; a processor for; a. determining a desired average linear velocity of the fluid flow according to the desired operating system parameter, b. determining an actual average linear velocity of the fluid flow according to the sensed plurality of actual operating condition parameters; c. determining, as a function of a predetermined relationship of the desired average linear velocity to the actual average linear velocity, the amount of fluid flow to cause the actual average linear velocity to substantially equal the desired average linear velocity; and an interface for providing a control signal representative of the determined fluid flow amount to the fluid flow controller. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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Specification