GB2454783A - HPLC constant flow pump to enable low-flow operation, wherein thermal-based sensors are contained within an isothermal block - Google Patents
HPLC constant flow pump to enable low-flow operation, wherein thermal-based sensors are contained within an isothermal block Download PDFInfo
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- GB2454783A GB2454783A GB0820564A GB0820564A GB2454783A GB 2454783 A GB2454783 A GB 2454783A GB 0820564 A GB0820564 A GB 0820564A GB 0820564 A GB0820564 A GB 0820564A GB 2454783 A GB2454783 A GB 2454783A
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- flow
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- sensors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
- B01D15/08—Selective adsorption, e.g. chromatography
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/28—Control of physical parameters of the fluid carrier
- G01N30/32—Control of physical parameters of the fluid carrier of pressure or speed
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D11/00—Control of flow ratio
- G05D11/02—Controlling ratio of two or more flows of fluid or fluent material
- G05D11/13—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means
- G05D11/131—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means by measuring the values related to the quantity of the individual components
- G05D11/132—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means by measuring the values related to the quantity of the individual components by controlling the flow of the individual components
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D16/00—Control of fluid pressure
- G05D16/04—Control of fluid pressure without auxiliary power
- G05D16/06—Control of fluid pressure without auxiliary power the sensing element being a flexible membrane, yielding to pressure, e.g. diaphragm, bellows, capsule
- G05D16/08—Control of liquid pressure
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/28—Control of physical parameters of the fluid carrier
- G01N30/32—Control of physical parameters of the fluid carrier of pressure or speed
- G01N2030/326—Control of physical parameters of the fluid carrier of pressure or speed pumps
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Automation & Control Theory (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Measuring Volume Flow (AREA)
Abstract
Apparatus 100, for delivering liquid in a capillary system, comprises first 102 and second 104 pumps in fluid communication with first 101 and second 103 flow paths respectively. Each flow path 101,103 has a thermal-based flow sensor 106,112 disposed in the path, the sensors 106,112 being configured to produce a signal and contained in an isothermal block 122. The apparatus 100 also comprises means 120 for adjusting the output of the first 102 and/or second 104 pumps in response to the signals produced by the sensors 106,112. The sensors 106,112 may be in fluid communication with a fluidic mixer 110. The capillary system may be a high pressure liquid chromatography system having flow rates in the range of 1nL/min to 100žL/min.
Description
CLOSED LOOP FLOW CONTROL OF A HPLC CONSTANT
FLOW PUMP TO ENABLE LOW-FLOW OPERATION
FIELD OF THE INVENTION
The present invention relates to a flow sensing method and apparatus and more particularly to a flow sensing method and apparatus used to monitor and provide feedback to a closed-loop flow control of an analytical-scale high performance liquid chromatography (HPLC) system which enables the delivery of stable flow to a nano-scale chromatographic system using a micro-scale or normal scale chromatographic pump.
BACKGROUND OF TILE INVENTION
The recent interest in nano-scale chromatography (<1 p11mm flow rates) has prompted HPLC instrument manufacturers to try to develop pumps capable of delivering lower flow rates. Unfortunately, typical analytical-scale HPLC pump technology does not scale well to these low flow rates as the constant-flow open-loop analytical-scale pumps typically used for analytical-scale chromatography (0.1-5 * mL/min) are good flow sources above -0.1 tIJmin, but below these flow rates, * * 20 inaccuracies due to solvent compression and seal, fitting or check-valve leakage compromise their flow accuracy.
* S 55 * * Traditional plunger displacement pumping systems have been successful in delivering stable, accurate flows in the normal-scale and micro-scale high ** perfonnance liquid chromatography regimes. While normal-scale HPLC is * : * 25 performed with mobile phase flow rates of about 0.1 -5.0 mLlmin and micro-scale HPLC is performed with mobile phase flow rates of about 1 -100 jtlJmin, nano-scale HPLC requires mobile phase flow rates in the 50-1000 nL1min range. Current plunger displacement pumping systems typically cannot deliver nano-scale HPLC flow rates with reliability and accuracy.
One method for providing nano-scale flow rates in an HPLC system is to use a flow-divider which directs a majority of flow from the pump to a waste stream and a small portion of the pump output to the HPLC working stream (i.e., to the liquid chromatography column). A split restrictor in the waste stream and/or the working stream controls the split ratio of the system. Normal-scale or micro-scale HPLC pumps can be used in split flow mode to produce nano-scale HPLC flow rates in the working stream.
Unfortunately, in order to operate a HPLC system in split-flow mode the user must calculate the split ratio of the system. To calculate the split ratio, the user must know the permeabilities of both the split restrictor and the chromatographic system (i.e. the packed column). These permeabilities are used to calculate the flow rate that must be supplied by the nonnal-scale or micro-scale HPLC pump to produce the desired flow through the chromatographic system. Although it is possible to calculate split restrictor dimensions that should provide a desired split ratio, changes in permeability of either the split restrictor or chromatographic column over time cause unpredictable split ratio variations. Such variations result in unacceptable flow variations through the chromatographic column.
One possible solution to the problem of changing split ratios is to monitor the flow to the chromatographic colunm with an appropriate flow sensor. Fluid flow rates can be determined by measuring the pressure of a liquid flowing through a restrictor. * **
*. Assuming a constant viscosity, the back pressure of liquid flowing through a restrictor *** * 20 will scale linearly with the flow rate of the liquid. The flow rate is measured by * placing a pressure transducer before and after a restrictor inline with the flow. Signals * from the pressure transducers are electronically subtracted and amplified to achieve a S.....
* high degree of common-mode noise rejection.
The permeability of the restrictor is chosen so that it provides sufficient back * * 25 pressure to produce a measurable pressure difference signal (E.P) in the flow ranges of interest but does not produce a significant back pressure for the pump. For example, a cm long, 25 J.tm inside diameter capillary will provide a back pressure of approximately 100 pounds per square inch (psi) for water flowing at 5 jtL/min. This permeability is sufficient for providing a flow measurement while not inducing much fluidic load on the pump.
However, pressure measuring flow sensors must be calibrated to compensate for the different viscosity of each fluid being measured. This creates a great disadvantage in liquid chromatography applications wherein fluid composition varies dramatically over the course of a chromatography run.
The present invention involves thermal flow sensing. Several companies including Sensirion AG, of Zurich, Switzerland, and Bronkhorst Nijverheidsstraat of Ruurio, The Netherlands, have been developing thermal flow sensors capable of monitoring flows in nlJmin ranges.
In the operation of these thermal flow sensors, heat introduced into a liquid filled tube/channel will disperse in both the upstream and downstream directions (i.e. due to thermal conduction or diffusion respectively). The tube of the flow sensing device is made from materials of low thermal conductivity (i.e. glass, plastic). A temperature profile will develop when a discrete section of the fluid in the tube is continuously heated, under a zero flow condition. The shape of this temperature profile will depend upon the amount of heat added to the fluid and the upstream and downstream temperatures of the liquid. Assuming identical upstream and downstream fluid temperatures, under a zero-flow condition, liquid temperatures measured at first and second sensor will be equal as thermal diffusion will be equal in * ** both directions. *.
If the liquid in the tube is permitted to flow, the fluid temperatures at the first and second sensor will depend upon the rate of liquid flux and the resulting heat : convection. As liquid begins to flow past the heated zone, a temperature profile develops, In addition to the symmetric diffusion of the heat, asymmetric convection : . of the heated fluid will occur in the direction of the fluid flow. Therefore, under * : * : 25 flowing conditions, fluid temperatures measured at the first and second sensor will be different.
Temperature measurements made at the first and second sensor are sampled, subtracted and amplified electronically in situ to provide a high degree of common-mode noise rejection. This allows discrimination of extremely small upstream and downstream temperature differences. By appropriate placement of temperature measurement probes (i.e., first and second sensor) and/or by changing the amount of heat added to the flowing liquid, temperature measurement can be made at inflection points along the temperature profile. Measurement at the inflection points maximizes the upstream/downstream tT response to flow rate change.
However, like pressure measuring flow sensors which must be calibrated to compensate for the different viscosity of each fluid being measured, thermal based flow sensors also need such calibration. This at times creates a disadvantage in liquid chromatography applications wherein fluid composition varies dramatically over the course of a chromatography run.
Other pump solutions for creating the low flow rates required by nano-scale LC involve single-stroke syringe pumps. These pumps have a fixed delivery volume.
As a result run times may be limited by the length of the pump stroke. Time is required between each run to refill the pump. During this refill cycle, the chromatographic system must depressurize, then re-pressurize to start the next run.
Repeated depressurizationlre-pressurization cycles unfortunately have a deleterious effect on the chromatographic column.
Additionally, Nano-scale LC systems are often coupled to mass spectrometers.
Electro-spray interfaces typically used in LC-coupled mass spectrometers are most stable when constantly flowing. The stop-flow conditions existing during refill cycles * ** of syringe-type pumps as noted above may destabilize the electro-spray mass S..
**.* 20 spectrometry interface.
S
* .SS** * I
* :": SUMMARY OF THE INVENTION
*:* The invention provides an apparatus for delivering a liquid in a capillary * : * system which apparatus comprises a first pump in fluid communication to a first flow path carrying a first portion of a liquid from said first pump to a first thermal-based flow sensor, said first thermal-based flow sensor being operatively disposed in said first flow path and configured to produce a first signal, a second pump in fluid communication to a second flow path carrying a second portion of a liquid from said second pump to a second thermal-based flow sensor, said second thermal-based flow sensor being operatively disposed in said second flow path and configured to produce a second signal and means for adjusting the output of at least one of the first and second pumps in response to at least one of the first and second flow rate signals and wherein said first and second thermal-based sensors are contained within an isothermal block.
According to a feature of the invention, the first and second thermal-based flow sensors may be in fluid communication with a fluidic mixer. According to another feature of the invention, said capillary system may comprise a high pressure liquid chromatography (HPLC) system having flow rates in the range of InJJmin to 1 00i.LLJmin.
In a practical application of the invention, the analytical-scale constant flow-source HPLC pumps used are modified commercially available pumps. These commercially available pumps are retro-fitted with minor hardware and/or firmware changes to enable low-flow delivery. Typically, analytical-scale HPLC pumps use stepper-motor driven linear actuators. Depending on the pump architecture, the change required to enable low-flow delivery involves modifiing the gearing of the pump drive mechanism offering a higher incremental drive resolution. Changes to the firmware/stepper motor drive electronics increasing the micro-stepping resolution of the stepper motor drive is contemplated. It is envisioned, for example, that minor modifications to the pumps firmware by increasing the micro-stepping resolution * ** *** ** from 10 iSteps to 100 tSteps enables low-flow operation. * S
hi the present embodiment of the invention, an apparatus for delivering a liquid in a * : capillary system includes two flow-source pumps and two associated thermal sensors.
Advantages of the invention include correction of the flow output of a typical, analytical-scale (0.1-5 mlJmin) HPLC pump enabling accurate and precise flow *S..
* 25 delivery at capillary (<0.1 mLlmin) and nano-scale (<1 pLlmin) HPLC flow rates.
The present invention permits retrofitting and reuse of existing pump technology providing cost and supply advantages.
A further advantage of the inventive apparatus and method is that there are significant advantages to reusing existing pump technology with the flow correcting apparatus according to the invention. These advantages include cost savings associated with development, sales and service training and inventory management.
Furthermore, traditional constant-flow J{PLC pumps are ideally suited for use according to the invention.
BRIEF DESCRIPTION OF THE DRAWING
The foregoing and other features and advantages of the present invention will be more fully understood from the following detailed description of an embodiment of the invention, taken in conjunction with the accompanying drawing in which: FIG. 1 is a schematic representation of a closed-loop flow control binary solvent delivery system using thermal based flow sensors.
DETAILED DESCRIPTION
An embodiment of the invention involves the use of a pair of flow sources. A "flow source" is herein understood to be a source that provides a fluid having a flow rate associated with a volume per unit of time. For example, one type of flow source : * includes a piston that displaces a volume of fluid per unit of time. A particular value * :* of volume per unit of time is determined, for example, by controlling the linear velocity of the piston, and by selecting a piston diameter, in the case of a piston * 20 having a circular cross-section. Thus, for example, the velocity of the piston *S**** * multiplied by the area defines a volumetric flow rate. This flow rate is analogous to, for example, a current source in an electrical circuit, which provides an amount of *: chargeperunitoftime.
A flow source is distinct from a pressure source, such as a pneumatic air supply with a regulator. A pressure source is analogous to, for example, a voltage in an electrical circuit. Pressure (voltage, in the analogy) induces a particular flow rate (a current in the analogy) if impressed upon a fluid restriction (a resistor, in the analogy). Thus, while a flow source has the ability to independently determine a flow rate, a pressure source typically does not independently determine a flow rate. Rather, a pressure source works in cooperation with other component(s) of a flow path, such as a flow-restrictor component, to determine a flow rate through the flow path.
Turning to FIG. 1., a schematic of a closed loop system 100 according to the invention is shown. A first pump 102 and a second pump 104, which are flow-source pumps such as, for example, analytical-scale constant flow-source I{PLC pumps.
These analytical-scale constant flow-source pumps are any suitable pumps such as commercially available pumps (for example, the WATERS� 515, 1 525u, and Acquity pumps, available from Waters Corporation, Milford, MA, USA, or the like.) The first pump 102 and second pump 104 are fitted with minor hardware and/or firmware changes to enable low-flow delivery. Typically, analytical-scale HPLC pumps use stepper-motor driven linear actuators. Depending on the pump architecture, change required to enable low-flow delivery involves modifying the gearing of the pump drive mechanism. These modifications to the gearing of the pump drive mechanism offer a higher incremental drive resolution. It is contemplated within the scope of the invention that changes to the firmware/stepper motor drive electronics to increase the micro-stepping resolution of the stepper motor drive may be used to enable low-flow delivery. Minor modifications to the pumps' firmware are made by increasing the micro-stepping resolution from about 10 jiSteps to about 100 Steps. This increased resolution allows low-flow operation. S...
.... 20 While it may be possible to develop a pump specifically designed to deliver flow compatible with nano-scale LC, there are significant cost and supply advantages to reusing existing pump technology with the flow correcting apparatus described * S S S*.
* above. Advantageously, traditional constant-flow HPLC pumps are ideally suited for this application.
* : * : 25 With further reference to FIG. I, the first pump 102 is in fluid communication to a first inline sensor 106. The first inline sensor 106 is a thermal-based flow sensor, available from, for example, Bronlthorst High-Tech B.V., Ruurlo, The Netherlands, and Sensirion AG, Zurich, Switzerland.
As shown in FIG. 1, in a first operating path 101 flow from the first pump 102 is in fluid communication with the first inline sensor 106. The first inline sensor 106 is in fluid communication with a fluidic mixer 110. In a second operating path 103, the second pump 104 is in fluid communication with a second inline thermal based flow sensor 112. The second inline sensor 112 is in fluid communication with the fluidic mixer 110. In operation, temperature measurement at the first inline senor 106 and the second inline sensor 112 will be proportional to the flow delivered by the first pump 102 and the second pump 104 respectively.
In operation, a system controller 120 will interpret temperatures measured by the sensors 106, 112 using previously obtained calibration constants and calculate flow rates being delivered by the first pump 102 and second pump 104. The system controller 120 will modify flow rates delivered by the pumps 102, 104 to adjust for any error between measured flow rates and set point flow rates. Flow inaccuracies resulting from solvent compressibility, pump or system leakage are corrected. One advantage of the system according to the present invention is that parasitic losses that at times arise due to pressure type sensors are avoided.
Persons having ordinary skill in the art should appreciate that additional control circuitry (not shown) maybe required between the output of the sensors 106, 112 and the input of the pumps 102, 104. For example, additional control circuitry may be implemented to condition the output signal for use as an appropriate control input to the particular pump being used. Circuit components such as buffers, * ** inverters, amplifiers and/or microcontrollers, for example, can be used to implement U...
*** 20 the control circuitry according to a number of methods that are well known to those :: skilled in the art.
In this embodiment of the invention the controller 120, a microcontroller or microprocessor, is implemented between the sensor output and the control input of the : respective pumps 102, 104. The controller 120 can be programmed and configured, * 25 for example, to adjust the flow rate of the pumps 102, 104 to a setting appropriate for maintaining a respective flow rate producing a selected gradient composition.
For consistent and reproducible results the sensors 106, 1 l2are contained in an isothennal block 122.
Flow sensors used in the inventive flow-correcting apparatus will need to be calibrated for each solvent used in the system. Commercially-based thermal flow sensors have different responses depending on the thermal capacity of the measured a fluid. Because constant flow pumps are used in this system, calibration of these flow sensors can be accomplished easily by flowing known flow rates through the sensors to determine their response. This calibration routine can be done at relatively low pressures where pump leakage and solvent compressibility is not an issue, and steady S open-loop flow delivery can be expected.
Because a known flow rate is being delivered by constant-flow pumps, the error between the delivered flow and the flow measured by the flow sensors can be used to diagnose pump leakages. It is contemplated within the scope of the invention that system intelligence can be implemented in the flow controller 120 to correlate flow error within the pump cycle identifying where leakages are occurring. In typical two-plunger reciprocating or serial flow delivery pumps, flow errors can be correlated to the seal or check valve responsible for the leakage. This level of diagnostics allowed by such system intelligence according to the invention is useful for troubleshooting pump failure allowing for early diagnosis and suggested corrective action preventing costly pump failure.
By using analytical-scale continuous flow HPLC pumps, high flow rates can be used to prime the system when solvent change over is necessary. For nano-flow systems that employ low-flow only pumps, this priming operation may take a * ** **.* significant amount of time. *..*
Although the various embodiments of the present invention are described for use in measuring nano-scale flow rates in an I{PLC system, persons skilled in the art should appreciate that the present invention can be used to measure and control a : *: variety of different capillary systems, or fluid control and analysis systems. * .
Claims (4)
1. An apparatus for delivering a liquid in a capillary system which apparatus comprises a first pump in fluid communication with a first flow path carrying a first portion of a liquid from said first pump to a first thermal-based flow sensor, said first thermal-based flow sensor being operatively disposed in said first flow path and configured to produce a first signal, a second pump in fluid communication with a second flow path carrying a second portion of a liquid from said second pump to a second thermal-based flow sensor, said second thermal-based flow sensor being operatively disposed in said second flow path and configured to produce a second signal, means for adjusting the output of at least one of the first and second pumps in response to at least one of the first and second flow rate signals and wherein said first and second thermal-based sensors are contained within an isothennal block.
2. Apparatus according to claim 1, wherein the first and second thermal-based flow sensors are in fluid communication with a fluidic mixer. * .*
3. Apparatus according to any of the preceding claims, wherein said capillary system comprises a high pressure liquid chromatography (HPLC) system having flow rates in the range of lnLlmin to lOOpLImin.
S
* S. ..S * S
4. Apparatus substantially as hereinbefore described with : -: 25 reference to, and as shown in, the accompanying drawings.
S SSSSS * S
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0820564A GB2454783B (en) | 2004-05-21 | 2005-05-20 | HPLC constant flow pump to enable low-flow operation, wherein thermal-based sensors are contained within an isothermal block |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US57352804P | 2004-05-21 | 2004-05-21 | |
| GB0624464A GB2429785B (en) | 2004-05-21 | 2005-05-20 | Closed loop flow control of a hplc constant flow pump to enable low-flow operation |
| GB0820564A GB2454783B (en) | 2004-05-21 | 2005-05-20 | HPLC constant flow pump to enable low-flow operation, wherein thermal-based sensors are contained within an isothermal block |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0820564D0 GB0820564D0 (en) | 2008-12-17 |
| GB2454783A true GB2454783A (en) | 2009-05-20 |
| GB2454783B GB2454783B (en) | 2009-10-28 |
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| Application Number | Title | Priority Date | Filing Date |
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| GB0820564A Active GB2454783B (en) | 2004-05-21 | 2005-05-20 | HPLC constant flow pump to enable low-flow operation, wherein thermal-based sensors are contained within an isothermal block |
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| GB (1) | GB2454783B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015040391A1 (en) * | 2013-09-20 | 2015-03-26 | Micromass Uk Limited | Mass spectrometer |
| WO2016092023A1 (en) * | 2014-12-12 | 2016-06-16 | Ge Healthcare Bio-Sciences Ab | System for preparing solutions for chromatography |
| EP3086197A1 (en) * | 2015-04-21 | 2016-10-26 | Airbus Defence and Space, S.A. | Machine for mixing and successively applying sealant material |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004027535A1 (en) * | 2002-09-17 | 2004-04-01 | Eksigent Technologies, Llc | Flow control system |
| WO2004112960A2 (en) * | 2003-05-20 | 2004-12-29 | Eksigent Technologies Llc | Flow rate control |
-
2005
- 2005-05-20 GB GB0820564A patent/GB2454783B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004027535A1 (en) * | 2002-09-17 | 2004-04-01 | Eksigent Technologies, Llc | Flow control system |
| WO2004112960A2 (en) * | 2003-05-20 | 2004-12-29 | Eksigent Technologies Llc | Flow rate control |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015040391A1 (en) * | 2013-09-20 | 2015-03-26 | Micromass Uk Limited | Mass spectrometer |
| WO2016092023A1 (en) * | 2014-12-12 | 2016-06-16 | Ge Healthcare Bio-Sciences Ab | System for preparing solutions for chromatography |
| US10926191B2 (en) | 2014-12-12 | 2021-02-23 | Cytiva Sweden Ab | System for preparing solutions for chromatography |
| US11801456B2 (en) | 2014-12-12 | 2023-10-31 | Cytiva Sweden Ab | System for preparing solutions for chromatography |
| EP3086197A1 (en) * | 2015-04-21 | 2016-10-26 | Airbus Defence and Space, S.A. | Machine for mixing and successively applying sealant material |
| US10189035B2 (en) | 2015-04-21 | 2019-01-29 | Airbus Defence and Space S.A. | Machine for mixing and successively applying sealant material |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2454783B (en) | 2009-10-28 |
| GB0820564D0 (en) | 2008-12-17 |
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