GB2303885A - Pumping System - Google Patents

Description

1 PUMPING SYSTEM 2303885 The present invention relates to analytical

instruments and, more particularly, to pumping systems for use in analytical instruments.

Fluids at high pressure can be used as solvents in instruments for performing extraction, chromatography, and other related processes. One such fluid has been characterized as a supercritical fluid, which is a useful hybrid of a gas and a liquid, possessing gas-like viscosity, liquid-like density, and a diffusivity greater than a typical liquid solvent. The liquid-like density of a supercritical fluid imparts a variable liquid-like solvent power which is essentially a linear function of density over significant ranges in density. This allows the solvent power, usually considered a chemical interaction, to be set simply by adjusting a physical parameter, namely density or pressure.

Supercritical fluids are quite efficient to use for extraction of complex matrices. Either the isolated materials (extract) or the material remaining (raffinate) can be of interest. The process of isolation or extraction of solids by dense gasses or supercritical fluids is referred to as supercritical fluid extraction (SFE). The process of chromatography using mobile phases that are dense gases is characterized as supercriticai fluid chromatography (SFC). In S17C, the mobile phase is a fluid subjected to temperatures and pressures generally near its crifical point. Fluids at those conditions have densities much closer to liquids but often exhibit greater solute diffusion characteristics than liquids. SFC is thus sometimes regarded as being a necessary intermediate between gas chromatography (GC) and liquid chromatography (LC).

The pumping system is among the most costly components in an analytical instrument that uses fluids at high pressure. For example. instrumentation for performing SFC is much more expensive to manufacture, due to the requirements J01 ' 2 for operation at very high pressures, than instrumentation for performing GC. Conventional instrumentation for performing capillary SFC typically operate between 70 bar and 600 bar. In contrast, a typical gas chromatograph with pressure programming capability is generally operated at pressures less than 10 bar. As a result, the relatively high cost of SFC instrumentation has prevented many potental users from performing SIFC.

The development of suitable high pressure pumping systems has generally pursued three distinctly different pump designs: pneumatic amplifier, reciprocafing piston, and syringe.

A pneumatic amplifier pump includes a piston mounted between two adjacent pump chambers (a low pressure chamber and a high pressure chamber). The chambers have differing piston cross-sectionai areas and therefore offer a pressure amplification factor. Two known methods for filling the low pressure chamber are (a) providing a gas pressure which is regulated from a high pressure gas chamber or air pump and (b) delivering a water pressure from a high pressure LC pump, such as a reciprocating piston pump. However, the former method has heretofore been limited in its use to isobaric operation; accordingly, the pressure programming operations that are essential to SFE and SIFC applications are difficult to implement. The use of a reciprocating piston pump in the latter method, to deliver water to the low pressure chamber, allows pressure control of the SIFC fluid in the amplifier's high pressure chamber. However, such use of a reciprocating piston pump has been severely limited by its speed of response to pressure change and the rate of pressure ramp-up and rampdown.

Reciprocating piston pumps containing single, dual, or triple pump heads have been modified for S17C applications. A single pump head system with a pulse damper has been used for isocratic open tubular column and microbore packed column SFC applications where low flow rates and small pressure pulses can be dampened with a small damper and a column. However. for these and other applications, the typical reciprocating pump is noisy, requires substantial pulse dampening of its output, and usually requires some means for cooling of the pump head.

A syringe pump is thus the most widely utilized fluid delivery system for performing SFE and SFC. However the t ical s rin e pump exhibits a long and T m J j 3 frequent refill time; requires.an expensive, powerful motor and a motor driver power supply; and includes many parts that require servicing. The syringe pump is much more costly to build and operate than is desirable.

Accordingly, there remains a need for an inexpensive pumping system suitable for use in applications of high pressure fluids to analytical methods, such as SFE or WC.

In a first aspect of the present invention, we have found that complex pressure programming of a fluid at very high pressures can be provided by a novel pumping system that employs a pneumatic amplifier pump, a pressure regulator, and an electronic pressure control system. Electronic pressure control is applied to a first fluid such that the presence of the first fluid at a first fluid pressure in a low pressure chamber of the pneumatic amplifier pump allows a quantity of a second fluid present in a high pressure chamber of the pneumatic amplifier pump to be compressed to a pressure suitable for use in, for example, supercritical fluid applications. Such pressure programming has been found to accomplish or exceed the output pressures provided by a conventional high pressure fluid pumping system (such as a syringe pump), but at a lower cost and with greater reliability.

In a second aspect of the present invention, we have found that the aforementioned pumping system may be easily and inexpensively adapted for use in a capillary SFC instrument, for performing rapid separation of relatively nonvolatile and labile compounds.

instrument employs capillary WC columns.

The preferred embodiment of the SFC In a third aspect of the present invention, we have found that the 1 aforementioned pumping system may be employed in an instrument for performing supercritical fluid extraction of a component from a sample.

In a fourth aspect of the present invention, we have found that the aforementioned pumping system may be employed in an instrument for performing solid phase extraction of a component from a sample.

The preferred embodiment of a pumping system may be constructed according to the present invention to include a pneumatic amplifier pump and an electronic pressure control system for sensing the pressure of a first fluid provided 4 to a low pressure chamber in the pneumatic amplifier pump. The pressure of the first fluid is thus directly controlled to a setpoint pressure. The pressure of the first fluid can be maintained at the setpoint in accordance with a pressure program implemented in the electronic pressure control system. A quantity of a second fluid supplied to a high pressure chamber in the pumping system is thereby pressurized to a second fluid pressure in accordance with the amplification factor of the pneumatic amplifier pump. Hence, the second fluid pressure is indirectly controlled by the electronic pressure control system in its direct control of the first fluid pressure.

The contemplated pumping system may be integrated in an SFC instrument, wherein the pressurized second fluid may be directed to an injector for receiving a sample, and a mixture of the sample and the pressurized second fluid may then be provided to the inlet of a separation column. Sample components that are eluted at the column outlet are then detectable by a detector.

The contemplated pumping system may be integrated in an SFE instrument, wherein the pressurized second fluid may be directed to an extracton section for processing a sample.

The contemplated pumping system may be integrated in an solid phase extraction instrument, wherein the pressurized second fluid may be directed to an extraction section for collecting a sample.

This invention is more particularly pointed out in the appended claims and, with reference to the accompanying drawings, will be understood in its preferred embodiments in the following description.

Fig. 1 is a schematic illustration of a pumpirxg system constructed in accordance with the present:Lnvention.

FIG. 2A is a schematic illustration of an instrument that utilizes the pumping system of Figure 1 for performing capillary SFC- FIG. 2B is a schematic illustration of an instrument that utilizes the pumping system of Figure 1 for performing supercritical fluid extraction.

FIG. 2C and 2D are schematic illustrations of respective instruments that utilize the pumping system of Figure 1 for performing plural, simultaneous supercritical fluid extractions.

FIG. 2E is a schematic illustration of an instrument that utilizes the pumping system of Figure 1 for performing solid phase extraction.

FIG. 3 is a schematic illustration of a pneumatic amplifier pump operable in the system of Figure 1.

FIG. 4 is a schematic illustration of an electronic pressure control system for effecting electronic pressure control of the pumping system of Figure 1.

Preferred embodiments of the present invention will now be described with reference to Figures 1-4, wherein equivalent components are indicated by like nomenclature and reference designations. For clarity, the schematic representation of circuits beari-ng electronic signals are illustrated in single lines, whereas fluidbearing channels are indicated in double lines.

As shown in Figure 1, and in a particular feature of the present invention, a novel pumping system may be constructed to include a first fluid supply 10A, which is preferably a high pressure supply in the form of a high pressure gas cylinder of compressed gas, or an air pump. The first fluid supply 1 OA provides a gas such as compressed air or nitrogen through a flow restrictor 11 to a pneumatic amplifier pump 12. An electronic pressure control (EPC) system 14 is provided to control a pressure regulator 14A for the purpose of inducing a first controlled pressure in the first fluid. The pneumatic amplifier pump 12 receives a quantity of the first fluid at the first fluid pressure and a quantity of a second fluid from a second fluid supply 10B. That is, by operation of the EPC system to control the first fluid pressure and to control activation of a switching valve in the pneumatic amplifier pump 12, the first and second fluids may be caused to fill respective low and high pressure chambers in the pneumatic amplifier pump 12. The pressure of the first fluid in the pneumatic amplifier pump 12 causes the second fluid to be pressurized to a desired second fluid pressure. The flow of the second fluid from the pump 12. after being subjected to such controlled pressurization, is considered herein as the pressurized second fluid.

6 In particular, the desired pressures of the first and second fluids are programmable according to a pressure profile generated and applied to the first fluid by the EPC system 14. In other words, the pressure programming directly applied by the EPC system 14 to the first fluid is used to indirectly control the pressure of the second fluid.

The preferred pumping system includes a pressure sensor 20 to generate a pressure information signal representative of the pressure of the first fluid provided to the pneumatic amplifier pump 12, or in the alternative, a pressure sensor 20A to generate a pressure information signal representative of the pressurized second fluid as it is provided to injector 16. Because the sensors 20 or 20A may be subject to factors such as temperature changes or vibration, a solid-state pressure sensor is preferred so as to combine temperature compensating circuitry with digital control for accurate pressure control without the need for calibration.

In one preferred embodiment, the pressure regulator 14A is provided in the form of a modulating control valve and the EPC system 14 would be employed to cause the open time of an orifice in the valve to be modulated. Alternatively, in an embodiment wherein the pressure regulator 14A is provided in the form of a of a proportional control valve, the EPC system 14 would be employed to cause the amount of an open orifice in the valve to be modulated. Accordingly, the pressure regulator 14A is preferably provided in the form of a high pressure valve.

In the illustrated embodiment, the pressure information signal is provided to the EPC system 14 for providing forward pressure regulation of the first fluid. Other modes of pressure regulation of the first fluid are also contemplated by the present invention.

A pumping system constructed according to the present invention offers an advance over the pumping systems employed in conventional SFE and SFC systems because, for the first time, the implementation of one or more desired pressures of a supercritical fluid may be electronically implemented in the operation of a pneumatic amplifier pump. Such regulation is achieved primarily in the EPC system 14, to be described further herein, where a pressure set point and control voltage are established and used to control the pressure regulator 14A.

Tuming to Figure 2A, it will be recognized that an instrument 100 for performing SFC may be constructed wherein the pressurized second fluid is passed 7 through an injector 16 into the inlet of a capillary column 18. The sample to be separated is introduced by a sampling system, or as illustrated, by a syringe 15 inserted into the injector 16 to inject the sample into the flow of the pressurized second fluid, thus providing a sample fluid mixture. The column 18 is located within an oven 24 which maintains a temperature in the sample fluid mixture that may be necessary for supercritical or near-supercritical operation. The illustrated instrument 100 may then be employed to enable rapid separation of the sample in the sample fluid mixture as it travels through the capillary column 18. A suitable oven 18 and EPC system 14 are commercially available in the Hewlett-Packard Model 6890 Gas Chromatograph.

The preferred capillary column 18 for performing capillary SFC as described herein will generally employ a coated capillary or micropacked SFC: column structure having an inside diameter (i.d.) of less than about 500 micrometers. The useful i.d. range will usually be from about 25 to 200 micrometers, and more preferably from 50 to 100 micrometers. Column flow rate in such columns is generally less than 10 microliters per minute.

The outlet from the capillary column 18 is passed to the one or more analytical devices, e.g. a detector so as to produce a chromatogram. In the preferred embodiment, the outlet from the capillary column 18 is passed to a suitable GC detector 28 through a fluid restrictor 30. A suitable GC detector is a flame ionization detector (FID) such as is available in the Hewlett-Packard Model 6890 Gas Chromatograph.

Turning now to Figure 213, it will be recognized that a SFE instrument 101 may be constructed wherein the pressurized second fluid is pumped by the pump 12 through a sample that is contained in an extraction section 106. Because the sample is immersed in the flow path, the pressurized second fluid dissolves material from the sample, and thereafter encounters a pressure drop at a restrictor 108. The restrictor 108 functions as a restrictor causing a pressure drop in the high pressure solution of the sample components, such that the components in the dissolved material are recovered as they precipitate from the expanding sample fluid mixture.

As already mentioned, the sensor 20 may be variously located to provide a pressure sense signal to the EPC system 14. The sensor 20 may be located to permit the EPC system 14 to monitor the pressure of the first fluid in the low 8 pressure chamber of the pump 12. Alternatively, the sensor 20C may be employed as illustrated, in a position upstream from the extraction section 106; or as sensor 20D it could also be positioned downstream from the extraction section 106.

With reference to Figures 2C and 2D, one may appreciate that respective second and third preferred embodiments 102, 103 of an SFE instrument can be constructed to allow simultaneous extractions of samples in a plurality of extraction secfions 106A, 106B, 106C and respecbve extractors 108A, 108B, 108C. The SFE instrument 102 includes a single pump 12. The SFE instrument 103 includes a plurality of respective pumps 12A, 12B, 12C. Each pump 12A, 12B, 12C receives a first fluid supplied from a respective pressure regulator 14A, 14B, 14C. Each regulator is under the control of one of multiple control signals from a multi-channel EPC system 14M.

With reference to Figure 2E, one may appreciate that a preferred embodiment 104 of an solid phase extraction instrument can be constructed to allow simultaneous extractions of one or more components in plural sample fluids. The embodiment contemplates a plurality of sample containers SA, SIB each containing a sample fluid that may be supplied to the pump 12 as a second fluid for pressurization. That is, a switching valve 111 allows a selected stream of a sample fluid from either of sample containers SA or SIB to be compressed by the pump 12 according to the operation of the pumping system described herein. The pressurized second fluid is directed by a switching valve 112 to a selected one of a plurality of extraction cartridges 107A, 107B, 107C. Each cartridge 107A, 1079, 107C is filled with a preinstalled solid phase adsorbent material such that one or more components of interest in the pressurized second fluid (e.g., a trace element in a water sample) can be retained while the remainder of the pressurized second fluid is passed to a waste line W by a respective switching valve 109A, 109B, 109C. Upon discontinuing the flow of the second fluid stream from the sample containers SA, SIB, another flow of a second fluid in the form of a collection solvent is provided from a collection fluid supply SC, compressed by the pump 12, and directed to the appropriate one of the extraction cartridges 107A, 1076, 107C by the switching valve 112. The flow of the collection fluid through the extra(:,ion cartridge removes the component of interest and the resulting mixture is directed via a respective switching valve 109A, 109B, 109C to a collection vessel 11 1 OA, 11 OB, 11 OC. The 9 extraction cartridges 107A, 10713, 107C may be constructed as being packed with a suitable adsorbent medium, or filled with a relatively inert matrix that has been coated or impregnated with adsorbent medium. One example of a suitable adsorbent medium/matrix is a Teflon disc matrix impregnated with adsorbent material, and is commercially available as an Empore component from the 3M Company of Minneapolis, Minnesota.

As will now be understood with additional reference to Figure 3, the electronic pressure control (EPC) system 14 regulates the pressure of the first fluid provided to the pneumatic amplifier pump 12 so as to indirectly regulate the pressure of the second fluid. In accordance with this invention, the amplifier pump 12 includes a first fluid supply fitting 33A connected to a low pressure chamber 34, a switching valve 338 connected to a high pressure chamber 36, a floating piston 35 having low pressure seals 35A and high pressure seals 35B, and an optional cooling system 37. As shown, the piston 35 is shown in broken lines in a first position that occurs at the onset of a compression cycle, wherein the second switching valve 33B may be operated to allow a quantity of second fluid to fill the high pressure chamber. The piston 35 is also shown in solid lines in a second position that occurs at the end of the compression cycle. Between the onset and end of a compression cycle, the switching valve 338 may be operated to close the high pressure chamber 36 such that the quantity of second fluid is pressurized to a predetermined elevated pressure and is therefore ready for delivery at a very high pressure, e.g., in some applications, as a supercritical fluid.

A typical compression cycle will be understood as follows. The first fluid supply fitting 33A allows the low pressure chamber 34 to be equalized with a zero or low pressure set by the regulator 14A. The switching vpIve 33A is then set to a first position wherein the high pressure chamber 36 receives a flow of the second fluid from the second fluid supply 10B. As the second fluid is allowed to fill the high pressure chamber 36, the piston 35 is forced to its maximum downward position. Thereafter, the switching valve 33B is closed and the EFPC system 14 causes a pressurized flow of the first fluid from the pressure regulator 14A to the low pressure chamber 34. The pressure of the first fluid multiplied by the amplification factor causes the piston 35 to compress the second fluid in the high pressure chamber 36. The piston 35 moves upwardly, until a predetermined pressure of the second fluid is attained in the high pressure chamber 36, and the upward motion of the piston 35 stops.

The amplifier pump 32 is then ready to deliver the quantity of the second fluid at a pressure that is maintained according to the pressure of the first fluid in the low pressure chamber 34 and the pneumatic amplification factor (AF) of the pneumatic amplifier pump 32. The ratio of the piston cross-sectional area at the low pressure chamber 34 and the high pressure chamber 36 equals the pressure amplification factor from the low pressure chamber to the high pressure chamber.

When the switching valve is switched to a fluid delivery position, the quantity of second fluid, still under pressure, is available for use in an analytical instrument. During delivery, and as the piston 35 resumes its upward motion, the EPC system 14 may, in certain embodiments, be programmed to maintain control of the first fluid pressure to provide continued flow of the first fluid while the second fluid flows from the high pressure chamber 36 through the switching valve 338.

In another preferred embodiment of the invention, the control by the EPC system 14 causes the pressure of the first fluid in the low pressure chamber 34 to be adjusted so as to allow setpoint control of the second fluid pressure at one or more predetermined setpoints. As a result, the second fluid may be delivered at a sustained, selectable pressure or at a series of pressures.

In an SFC application, and depending upon the capacity of the column 18 and the duration of the chromatographic analysis, the piston 35 continues its upward motion until all of the second fluid is expelled from the high pressure chamber 36, or until the switching valve 33B is switched to a closed position, or both. To avoid a pressure discontinuity, or what is known as a ripple effect, during the reset phase, the preferred embodiment of the amplifier pump 32 is constructed such that: a) the maximum desired pressure of the second fluid can be consistently provided to the column 18, and b) at least one chromatograrn can be completed at such a maximum pressure before the piston reaches the end of its upward stroke. Other features of the construction of the amplifier pump 32 may accomplished according to principles known in the art; for example. the ratio of the cross-sectional area of the low pressure chamber with respect to the cross-sectional area of the high pressure chamber may be chosen to determine the requisite amplification factor (AF).

Preferred amplification factors are contemplated as ranging from 20 to 500. The first fluid may preferably be provided at selectable pressures of up to 15 bar, the second fluid is preferably provided at pressures up to 2000 bar. Hence, if a flow of first fluid is provided at a first fluid pressure of 10 bar, and the piston 35 provides an amplification factor of 100, the second fluid pressure may be set and maintained at 1,000 bar.

Referring to Figure 4, the EPC system 14 preferably includes a user interface 38, computer 40, and controller 42. Although computer 40 is shown as a single block, such computer includes a central processing unit and all associated peripheral devices and other related electronic components. As such, computer 40 includes a memory 41 in which information and programming can be stored and retrieved by known methods.. . One or more additional computers 39 may provide control and data signals to computer 40. The programming associated with computer 40 which is utilized in relation to the present invention will be understood in connection with the following description. Computer 40 may also be programmed to maintain overall control of other systems associated with the instrument 100 or 102, as known in the art.

The user interface 38 preferably includes a display means. Consequently, indicating or prompt messages can be generated by computer 40 and displayed on user interface 38. A controller circuit 42 is utilized to control pressure regulator 14. Controller 42 is shown to include a second computer 44. which in the preferred embodiment incorporates an embedded microprocessor and its associated peripheral components.

Information may be entered into computer 40 by the user through way of user interface 38 or from other computers 39. Computer 40 operates to store the entered information into memory 41 for later access by computer 44. Initially parameters relating to the pressure profile to be effected by pressure regulator 14A during the analysis may be entered. In the preferred embodiment, desired pressure for any given moment in time during the analysis is calculated by computer 40 in relation to certain system operating parameters. Accordingly, the present invention contemplates the calculated desired pressure is used to provide a control signal.

In one preferred embodiment, the first fluid flow is subject to proportional electronic pressure control. The pressure regulator 14A is accordingly constructed 12 as a proportional control valve so as to open or close incrementally to maintain a desired pressure, with the change in open area approximately proportional to the change in controlling voltage supplied to the valve. In the forward regulated system as shown in Figure 1, the pressure sensor 20 is located downstream from the pressure regulator 14A. If the downstream pressure rises slightly, the pressure sensor voltage will rise. This voltage is transmitted via an appropriate signal line to the EPC controller 42, through an analog-to-digital (A/D) converter 50, and into a digital control circuit 44. In response, a new and slightly lower control voltage is returned to the pressure regulator 14A. The generated control signal may be in a digital form and thus can be converted to analog form by digital to analog converter 46 and appropriately amplified by amplifier 48 prior to transmission to pressure regulator 14A. The open area in the valve will be reduced slightly, resulting in a slightly smaller flow through the pressure regulator 14A and a slightly lower pressure at the pressure sensor 20. This feedback process occurs at relatively high frequency, resulting in very smooth and repeatable pressure control of the first fluid supplied to the pneumatic amplifier pump 12.

System operating parameters and system device parameters may also entered via user interface 38 into computer 40. In the preferred embodiment, the system operating parameters can include informabon representative of the desired pressure profile of the pressurized second fluid, the identification the type or composition of the fluid utilized: column outlet pressure; or the viscosity associated with a first fluid and/or second fluid if such information is not already present in memory 41 of computer 40. Such information would include the absolute viscosity of the particular fluid for various temperatures. The temperature range over which such a viscosity would be given directly corresponds to the temperature range or temperature profile to be exhibited by oven 24. System device parameters would include the length and diameter of column 18 or the characteristics of restrictor 108, and so on. Computer 40 can prompt the user to enter data related to the various operating parameters on the user interface 38. While the invention has been described and illustrated with reference to

specific embodiments, those skilled in the art will recognize that modifications and variations may be made without departing from the principles of the invention as 13 described hereinabove and as set forth in the following claims and their full range of equivalence.

It will be appreciated that the first fluid may be selected from a wide range of gases and liquids, such as air, nitrogen, helium, water, and hydraulic fluid. It will be appreciated that the second fluid can be selected from pure fluids, modified fluids, or tertiary fluids containing additives. As examples, pure fluids include: methanol or another alcohol, ethanol, nitrogen, helium, carbon dioxide, nitrous oxide, sulfur hexafluoride, and trifl uoro methane. Modified fluids include: methanol or another alcohol, acetonitrile, tetrahydrofuran, hexane and others mixed with one of the fluids mentioned under pure fluids above. Modified fluids can contain more than one modifier, more than one main fluid, or both more than one modifier and more than one fluid. Tertiary fluids may include any of the mixtures under modified fluids above with the addition of polar additives such as trifluoroacetic acid, isopropylamine, or a host of others mentioned in the literature.

14

Claims (1)

1. A pumping system for delivering a Ngh-pressure fluid, comprising: an electronic pressure control system for providing a control signal according to a pressure program: first and second fluid supplies for providing respective first and second fluids; a pressure regulator for receiving the first fluid and the control signal and, in response. for effecting a first fluid pressure in the first fluid. and a pneumatic amplifier pump exhibiting an amplification factor and having means for receiving a quantity of the first fluid at the first fluid pressure znd means for receiving a quantity of the second fluid: wherein the presence of the first fluid in the pneumatic amplifier pump at the first fluid pressure causes the quantity of the second fluid in the pneumadc amplifier pump to be pressurized according to the amplification factor, and whereby the pressurized second fluid is provided as the high-pressure fluid.

2. The pumping system of claim 1. further comprising a sensor for sensing at least one of the first fluid pressure and the pressure of the pressurized second fluid and for providing a respective data signal to the electronic pressure control system. and wherein the first fluid pressure is effected in response to the data signal.

3. The pumping system of claim 1. wherein the pneumatic amplifier pump further comprizes a low pressure chamber for receiving the first fluid at the first fluid pressure. a high pressure chamber for receiving the second fluid, and a piston movable within the low pressure chamber and the high pressure chamber.

The pumping system of claim 1, wherein the pressure regulator further comprises a valve responsive to the control signal.

5. The pumping system of claim 1, wherein the first fluid is a gas andthe first fluid supply further comprises a high pressure gas clamber.

1 13An MROW1XL Anik 3. The pumping system of claim 1, wherein the second fIL.Id is selected from the group of. pure fluids modified fluids. and terhary fluids containing additives.

7. The pumping syslem of claim 1. wherein the first fluid pressure is between 1 and 15 bar.

8. The pumping system of claim 1. whereir the second fluid pressure is effected at a pressure of between 1 and 2000 bar.

-9. The pumping system of claim 1, wherein the electronic pressure control system further comprises means for determining the pressure program.

1 10. An instrument for performing supercriticaj fluid chromatography with respect to a sample. comprising: a pumping system for delivering a superchfical fluid, including: an electronic pressure control system for providing a control signal according to a pressure program; first and second fluid supplies for providing respective first and second fluids: a pressure regulator for receiving the first fluid and the control signal and. in response. for effecting a first fluid pressure in the first fluid, and a pneumatic amplifier pump exhibiting an amplification factor and having means for receiving a quantity of the first fluid at the first fluid pressure and means for receiving a quantty of the second fluid'. wherein the presence of the first fluid in the pneumatic amplifier pump at the first fluid pressure causes the cuantity of the second fluid in the pneumatic amplifier pump to be pressurized according to the amplification factor whereby the pressurized second fluid is provided as a supercritical fluid: an injector for combining the sample and,t%,e supercr.fical fluid in a sample fluid mixture., a separation column for receiving the sample fluid mixture and eluting a sample component. and b.6"r" IA 1 16 -a detector for determining the presence of the sample component The instrument of claim 10, wherein the separation column ftirther comprises capillary column.

12. The instrument of claim 11. wherein the capillary column fLx:her comprises an internal diameter in the range of 25 to 200 micrometers.

13. The instrument of claim 10, furiher comprising a sensor for sensing at least one of the first and second fluid pressures and for providing a respecLve data signal to the electroric pressure control syst=tn, and wherein the second Puid pressure is effected in response to the data sigt. ...

14. The instrument of claim 10, wherein the second fluid pressure is provided at a pressure of between 1 and 2000 bar.

15. An instrument for performing supercrifical fluid extraction of a component in a sampie, comprising: a pumping system for delivering a supercritical fluid. including: an electronic pressure control system for providing a contrc. signal according to a pressure program. first and second fluid supplies for providing respective first and second fluids: a pressure regulator for receiving the first fluid and the control signal and, in response, for effecting a first fluid pressure in the first fluid. . and a pneumatic amplifier pump exhibiting an amplification factor and having means for receiving a quantity of the first fluid at the first fluid pressure and means for receiving a quantity of the second fluid-. wherein the presence of the first fluid in the pneumatic amplifier pump at the first fluid pressure causes the quantity of the second fluid in the pneumatic amplifier pump to be pressurized according to me amplification factor: whereby the pressurized second '.4uid is provided as a superchfical fluid:

fo"MD ORIC IIIII.J._ 1 C-211k 17 - an extraction section for receiving the sample and the supercritical fluid, and for dissolving the sample in the supercritical fluid to form a sample fluid mixture, and a restrictor for receiving the sample fluid mixture and for recovering the component of the sample.

16. The instrument of claim 15, further comprising a sensor for sensing at least one of the first and second fluid pressures and for providing a respective data signal to the electronic pressure control system, and wherein the second fluid pressure is effected in response to the data signal.

I 1 7, The instrument of claim 15. further wmpris..ig a plurality of extraction sections operrbly connected to the pumping system. the second fluid flow being provided to the plurality of extraction sections whereby a plurality of extractions may be performed simultaneously.

18. The instrument of claim 15, wherein the electronic pressure control system provides a plurality of control signals, and further comprising a plurality of respective pneumatic amplifier pumps. pressure regulators. and extraction sections. each of trie pneumatic amplifier pumps being provided a fwst fluid flow from a respective regulator at a respective pressure determined according to one of the control signals. and each of the pneumatic amplifier pumps being operable to provide a respective second fluid flow to a selected one of the plurality of extraction sections. whereby a plurality of extractions may be performed simultaneously.

19. An instrument for performing solid phase extraction of a component in a sample. comprising: a pumping system 'or delivering a hign-pressure nuid. including. an electronic pressure control sys!ern for providing a control signal according to a pressure program. first and second fluid supplies for providing respective first and second fluids. a pressure regulator for receiving the first fluid and the control signal and. in response. for effecting a first fluid pressure in the first fluid. and 1 1 j-4 BAD 18 pneumatic amplifier pump exhibiting an arripwrication facor and having means for receiving a quamity of the first f!:,zd at the first fluid pressure and means for receiving a quantity of the second fluid., wherein the presence of the first fluid in the pneumatic amplifier pump at the first fluid pressure causes the quantity of the second fluid in the pneumatic amplifier pump to be pressurized according to the amplification factor. whereby the pressurized second fluid is provided as a highpressure fluid, and an extraction cartridge having an adsorbent medium therein for receiving the high-pressure fluid and for extrac:ng the component into the adsorbent medium.

20. A method for delivering a mch-pressure f!uid. comprising providing an electronic pressure control signal according to a pressure program..

supplies..

providing first and second fluids from respective first and second flutd regulating the pressure of the first flu!d according to the control signal so as to effect a first fluid pressure in the first fluid: and providirina pneumatic arnp.lifter pump having a.'ow pressure chamber and a high pressure Ciamber; directing the secord fluid into the high pressure chamber.

directing the first fluid at the first fluid pressure into the low pressure chamber so as to effect a second fluid pressure in the second fluid whereby the second fluid is pressurized.. and providing the pressurized second fluid as the high-pressure fluid.

m--- _--BAD ORIGNAL, 11._--- CIL 19 21. A pumping system substantially as herein described with reference to the accompanying drawings.

22. An instrument substantially as herein described with reference to the accompanying drawings.

23. A method for delivering a high-pressure fluid substantially as herein described with reference to the accompanying drawings.