US5476000A — Retention time stability in a gas chromatographic…

Claim 1

Independent Claim 150 words

A method for performing a chromatographic analysis of a fluid in a separation column having an outlet subject to a barometric pressure p atm , 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 p atm ; 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.

Claim 2

Independent Claim 150 words

A method for performing a chromatographic analysis of a fluid in a separation column having an outlet subject to a barometric pressure p atm , 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 p atm ; 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.

Claim 3

Dependent Claim 25 words

The method of claim 1, wherein the information representative of a desired operation condition parameter includes data representative of desired inlet pressure (p i ).

Claim 4

Dependent Claim 23 words

The method of claim 1, wherein the information representative of a desired operating condition parameter includes data representative of a fluid flow rate.

Claim 5

Dependent Claim 34 words

The method of claim 1, wherein the information representative of a desired operation condition parameter includes data representative of a desired average linear velocity of the fluid at the column outlet (μ o ).

Claim 6

Dependent Claim 68 words

The method of claim 1, wherein the fluid flow control is provided by a signal-controlled inlet pressure valve, and the step of controlling the fluid flow further comprises computing an adjusted inlet pressure that will adjust the actual average linear velocity to the desired average linear velocity, and further comprising the step of applying a control signal representative of the adjusted inlet pressure to the inlet pressure valve.

Claim 7

Dependent Claim 72 words

The method of claim 1, wherein the fluid flow control is provided by a signal-controlled volumetric flow controller, and the step of determining an adjustment to the fluid flow further comprises computing an adjusted volumetric flow rate that will adjust the actual average linear velocity to the desired average linear velocity, and further comprising the step of applying a control signal representative of the adjusted volumetric flow rate to the flow controller.

Claim 8

Dependent Claim 80 words

The method of claim 1, wherein the step of determining the actual average linear velocity is performed in accordance with an actual operating condition parameter selected from the following group: Tc=Column Temperature (Absolute Temperature), Ts=Standard Ambient Temperature (Absolute Temperature), Ps=Standard Ambient Pressure (referenced to 1 atm=760 torr), d=Column diameter, L=Column length, p i =Inlet Pressure, p o =Outlet Pressure, μ o =Linear velocity of fluid at column outlet, μ=Average linear velocity of fluid, F co =column volumetric flow η=Fluid Viscosity.

Claim 9

Dependent Claim 38 words

The method of claim 1, wherein the relationship is provided according to the formula: μ.sub.ref ≡μ.sub.actual ( 8) wherein μ ref =desired average linear velocity, and μ actual =the actual average linear velocity, respectively, of the fluid flow.

Claim 10

Dependent Claim 12 words

The method of claim 8, wherein the fluid comprises a carrier gas.

Claim 11

Dependent Claim 46 words

The method of claim 8, wherein the step of sensing a plurality of operating condition parameters includes receiving a first sense signal representative of the separation column inlet pressure p i and a second sense signal representative of the separation column outlet pressure p o .

Claim 12

Dependent Claim 41 words

The method of claim 10, wherein the step of sensing a plurality of operating condition parameters includes referencing one of the first sense signal and the second sense signal to a signal representative of the ambient barometric pressure p atm .

Claim 13

Dependent Claim 72 words

The method of claim 9, wherein the relationship is provided according to the formula: ##EQU8## where: p i is the absolute inlet pressure, p id is the inlet pressure provided as a desired operating condition parameter, p o is the outlet pressure, p or is the sensed barometric pressure, p gd is the desired gauge pressure as a desired operating condition parameter, and p o1atm is the outlet pressure at 1 atmosphere.

Claim 14

Dependent Claim 58 words

The method of claim 9, further comprising the steps of: providing the fluid flow from the separation column outlet to a detector; and combining a support gas with the fluid flow to the detector, wherein the step of sensing a plurality of operating condition parameters includes receiving a third sense signal representative of a detector support gas pressure.

Claim 15

Dependent Claim 32 words

The method of claim 9, wherein a sample is injected into said fluid through an injection port, and wherein the flow of said carrier gas is controlled upstream from said injection port.

Claim 16

Dependent Claim 31 words

The method of claim 9, wherein a sample is injected into said fluid through an injection port, and wherein the flow of said fluid is controlled downstream from said injection port.

Claim 17

Dependent Claim 184 words

Apparatus for performing a chromatographic analysis of a fluid in a separation column having an outlet subject to a barometric pressure p atm , comprising: 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 p atm ; 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.

Claim 18

Dependent Claim 184 words

Apparatus for performing a chromatographic analysis of a fluid in a separation column having an outlet subject to a barometric pressure p atm , comprising: 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 p atm ; 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.

Claim 19

Dependent Claim 16 words

The apparatus of claim 16, wherein the information providing means further comprises an information input device.

Claim 20

Dependent Claim 11 words

The apparatus of claim 16, further comprising an information output device.

Claim 21

Dependent Claim 30 words

The apparatus of claim 16, further comprising a memory device for providing a program representing the predetermined relationship of the desired average linear velocity to the actual average linear velocity,.

Claim 22

Dependent Claim 28 words

The apparatus of claim 16, wherein the fluid flow controller further comprises an inlet pressure valve, and the determined fluid flow amount further comprises an adjusted inlet pressure.

Claim 23

Dependent Claim 29 words

The apparatus of claim 16, wherein the fluid flow controller further comprises a volumetric flow controller, and the determined fluid flow amount further comprises an adjusted volumetric flow rate.

Claim 24

Dependent Claim 12 words

The apparatus of claim 16, wherein the fluid comprises a carrier gas.

Claim 25

Dependent Claim 30 words

The apparatus of claim 16, wherein the plurality of transducers includes a pressure sensor for providing a first sense signal representative of the separation column inlet pressure p i .

Claim 26

Dependent Claim 29 words

The apparatus of claim 23, wherein the plurality of transducers includes a pressure sensor for providing a sense signal representative of the separation column outlet pressure p o .

Claim 27

Dependent Claim 37 words

The apparatus of claim 16, wherein the predetermined relationship is provided according to: μ.sub.ref ≡μ.sub.actual ( 8) wherein μ ref =desired average linear velocity, and μ actual =the actual average linear velocity, respectively, of the fluid flow.

Claim 28

Dependent Claim 15 words

The apparatus of claim 25, wherein the predetermined relationship is further provided according to: ##EQU9##

Claim 29

Dependent Claim 37 words

The apparatus of claim 16, further comprising an injection port wherein a sample may be injected into said fluid, and wherein the fluid flow controller is located to control the fluid flow upstream from said injection port.

Claim 30

Dependent Claim 37 words

The apparatus of claim 16, further comprising an injection port wherein a sample may be injected into said fluid, and wherein the fluid flow controller is located to control the fluid flow downstream from said injection port.

Claim 31

Dependent Claim 53 words

The apparatus of claim 16, further comprising: detector for receiving the fluid flow from the separation column outlet; means for combining support gas with the fluid flow to the detector; and pressure sensor for providing a sense signal representative of an actual operating parameter in the form of the detector support gas flow.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1998-12-18	1999-06-19	1999-12-19	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2002-12-18	2003-06-19	2003-12-19	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2006-12-18	2007-06-19	2007-12-19	$7700.00	Window Closed / Lapsed

Retention time stability in a gas chromatographic apparatus

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