GB2495777A

GB2495777A - Flow sensor stabilisation by adjusting temperature gradient

Info

Publication number: GB2495777A
Application number: GB1118229.2A
Authority: GB
Inventors: Uwe Effelsberg
Original assignee: Agilent Technologies Inc
Current assignee: Agilent Technologies Inc
Priority date: 2011-10-21
Filing date: 2011-10-21
Publication date: 2013-04-24
Anticipated expiration: 2031-10-21
Also published as: GB2495777B; GB201118229D0

Abstract

A sensor array for a fluid handling system, particularly for controlling the mobile phase drive to a sample separation system such as a high performance liquid chromatography application, wherein the sensor array comprises a plurality of flow sensors 82, 84, 86 each configured for detecting data indicative of a flow of the fluid, a fluid conduit 88 in fluid communication with the plurality of flow sensors 82, 84, 86 and configured for conducting the fluid, a temperature gradient detecting unit comprising temperatures sensors 94, 96 and configured for detecting temperature gradient data indicative of a spatial temperature gradient in the sensor array, and a temperature regulating unit which activates heating units 99, 97 configured to spatially regulate temperature in the sensor array in response to the detected temperature gradient data to thereby stabilize the spatial temperature gradient over time. The flow sensors 82, 84, 86, the heating units 99, 97 and the fluidic conduits 88 may be integrated within a substrate 900.

Description

SENSOR STABILIZATION BY ADJUSTING TEMPERATURE GRADIENT

BACKGROUND ART

[0001] The present invention relates to an array of flow sensors, particularly for controlling a mobile phase drive, more particularly to a sample separation system such as a high performance liquid chromatography application.

[0002J In high performance liquid chromatography (HPLC, see for instance http://en.wikipedia.orci/wiki/HPLC), a liquid has to be provided usually at a very controlled flow rate (e. g. in the range of microliters to milliliters per minute) and at high pressure (typically 20-1 00 MPa, 200-1000 bar, and beyond up to currently 200 MPa, 2000 bar) at which compressibility of the liquid becomes noticeable. For liquid separation in an HFLC system, a mobile phase comprising a sample fluid with compounds to be separated is driven through a stationary phase (such as a chromatographic column), thus separating different compounds of the sample fluid.

[0003] For controlling a pump in a HPLC, the flow of fluids may be measured at various positions along a fluidic path. This can be done by flow sensors providing data indicative of the fluid flow and being used for controlling the pump. The signal of the flow sensors may depend on the temperature.

[0004] W02005/113457 A2 discloses a method and an apparatus for monitoring and controlling nano-scale flow rate of fluid in the operating flow path of a HFLC system to provide fluid flow without relying on complex calibration routines to compensate for solvent composition gradients typically used in HPLC. The apparatus and method are used to correct the flow output of a typical, analytical-scale HPLC pump to enable accurate and precise flow delivery at capillary and nano-scale HPLC flow rates.

[0005] US 6,779,712 B2 discloses a flow sensor comprising a substrate with integrated heat source and temperature sensors. solder bumps are arranged on the heat source and the temperature sensors and the substrate is attached to the outside of a tube using flip chip technology. Preferably, the outside of the tube is structured for being wetted at appropriate positions by the solder. This allows to assemble the sensor easily and accurately.

[0006] However, the temperature dependence of the performance of flow sensors may still be a challenge. In chromatography a solvent gradient is a typical method parameter. The flow through the individual sensors may change over time.

The sensors typically have a temperature higher than the environment. Therefore the heat transfer into the sensor array is changing. This may cause a change in temperature and in temperature gradient across the sensor array. This may result in changed sensor response. The accuracy of the sensors is hence compromised.

DISCLOSURE

[0007] It is an object of the invention to provide a sensor array for a fluid handling system being operable in a reliable way. The object is solved by the independent claims. Further embodiments are shown by the dependent claims.

[0008] According to an embodiment of the present invention, a sensor array for a fluid handling system for handling a fluid is provided, wherein the sensor array comprises a plurality of flow sensors each configured for detecting data indicative of a flow of the fluid, a fluid conduit in fluid communication with the plurality of flow sensors and configured for conducting the fluid, a temperature gradient detecting unit configured for detecting temperature gradient data indicative of a spatial temperature gradient in the sensor array, and a temperature regulating unit configured to spatially regulate temperature in the sensor array in response to the detected temperature gradient data to thereby stabilize the spatial temperature gradient over time.

[0009] According to another embodiment of the present invention, a fluid handling system for handling a fluid is provided, wherein the fluid handling system comprises a sensor array having the above mentioned features, a pumping system configured to drive the fluid through the fluid handling system, and a drive unit configured for driving the pumping system based on the detected data indicative of a flow of the fluid.

[0010] According to still another embodiment of the present invention, a method of handling a fluid using a sensor array is provided, wherein the method comprises detecting data indicative of a flow of the fluid by a plurality of flow sensors, the fluid being conducted through a fluid conduit in fluid communication with the plurality of flow sensors, detecting temperature gradient data indicative of a spatial temperature gradient in the sensor array, and spatially regulating temperature in the sensor array in response to the detected temperature gradient data to thereby stabilize the spatial temperature gradient over time.

[0011] In the context of this application, the term "fluid" may particularly denote any liquid, any gas, any mixture of liquid and gas, optionally comprising solid particles. Particularly, analytes in liquid chromatography are not necessarily liquids, but can be dissolved solids or dissolved gases.

[0012] In the context of this application, the term "fluid handling system" may particularly denote any fluidic system having the capability of processing a fluid. For instance, a fluid may be conducted from a fluid inlet towards a fluid outlet.

Optionally, at least one fluid processing element (such as a fluidic channel or a chromatographic separation column) may be arranged between the fluid inlet and the fluid outlet. A fluid handling system may be, for instance, a fluid conveying system, a fluid purification system, or a fluid separation system.

fOOl 3] In the context of this application, the term "flow sensor" may particularly denote any sensor being capable of providing information indicative of a flow rate of a fluid flowing through a conduit, particularly in terms of flowing fluid volume per time interval (mI/mm) or flowing mass per time interval (g/min). The flow sensor may either directly or indirectly allow to determine the value of the flow rate, i.e. may directly measure the flow rate or may measure another parameter which may then be evaluated so as to derive the flow value. Particularly, such a flow sensor may have a temperature dependent sensing characteristic.

[0014] In the context of this application, the term "fluid conduit" may denote any capillary, groove in a substrate or other lumen defining a path along which a fluid may flow along the fluidic system.

[0015] In the context of this application, the term "spatial temperature gradient" may particularly denote a temperature distribution over the spatial extension of the sensor array or part thereof. In other words, the temperature within the sensor array may be a function of position within the sensor array and may be spatially varying.

I.e., usually not the entire sensor array is at a defined single temperature value, but in contrast to this a distribution of temperature values over the volume of the sensor array may be present. In an embodiment, the spatial temperature gradient is different from zero.

[0016] In the context of this application, the term "spatially regulate temperature" may particularly denote an adjustment of the temperature in dependency of a position within the sensor array. For instance, a spatially dependent impact of heating energy or cooling energy into specific portions of the sensor array may be adjusted. By setting the thermal energy at specific positions or spatial portions within the sensor array it is possible to manipulate the spatial temperature gradient over the sensor array.

[0017] In the context of this application, the term "stabilizing the spatial temperature gradient over time" may particularly denote taking any measure so as to prevent a continued drift of the temperature gradient within the sensor array away from an initial temperature gradient. Such a stabilization may be performed in order to maintain the sensor array continuously at the same temperature gradient characteristic. In case of identifying a deviation of an actual temperature gradient from an initial temperature gradient, supplying thermal energy to the system or removing thermal energy from the system may be performed so as to drive back the thermal gradient to its initial value.

[0018] According to an exemplary embodiment of the invention, a sensor array for a fluid handling system may be operated in an advantageous manner allowing for reproducible and meaningful as well as reliable sensor results. Without wishing to be bound to a specific theory, it has been surprisingly recognized that it is not the presence of a temperature gradient within the sensor array which deteriorates the measurement results, but that in contrast to this changes in a thermal gradient are the core of the deterioration of sensor results. Thus, exemplary embodiments of the invention do not seek to control the temperature within the sensor array so that the entire volume of the sensor array becomes an isotherm volume, but in contrast to this take measures to maintain an initially detected thermal gradient (and therefore a corresponding spatial temperature distribution) within the sensor array as constant as possible. Upon detecting deviations between an actual thermal gradient and a target value, thermal energy present in the sensor array may be adjusted in a spatially dependent way so as to regulate the system towards the initial thermal gradient.

[0019] Particularly in the field of liquid chromatography or, more generally, fluid separation systems, the provision of different solvents to be mixed in order to form a mobile phase needed for the separation can involve solvents with significantly different values of the heat capacity. For instance, in chromatographic applications a first solvent may be water and a second solvent may be an organic solvent such as ACN (acetonitrile). In such a scenario, the thermal gradient within the sensor array may be undesirably changed by the time-dependent change of the composition of the solvent which may result in a change of the spatial temperature gradient within the sensor array. Such a time-dependent change of the composition of the solvent may occur during a so-called chromatographic gradient run. Exemplary embodiments of the invention overcome such a problem by actively controlling the thermal energy supply to the sensor array, thereby suppressing artifacts in the sensor output resulting from a changed temperature distribution within the sensor array in response to a changed solvent composition.

[0020] Temperature stabilization or an isotherm arrangement needs a significant effort. The result is a direct function of the effort in this respect. In contrast to this, embodiments of the current invention keep the system in the state it is. No correction needs to be done until the heat transfer is changing and only the change is compensated. This way the accuracy is never compromised during baseline operation.

[0021] In the following, further exemplary embodiments of the sensor array will be explained. However, these embodiments also apply to the fluid handling system and to the method.

[0022] In an embodiment, the temperature regulating unit is configured to spatially regulate the temperature in the sensor array to thereby maintain the spatial temperature gradient constant over time. Therefore, the amount of thermal energy supplied to or removed from the sensor array as well as the spatial position of such a manipulation of the energy content of the sensor array may be performed in a manner that no or basically no change of the temperature gradient within the sensor array occurs. Therefore, particularly stable conditions are maintained over a sensor measurement time interval.

[0023] In an embodiment, the temperature gradient detecting unit is configured for detecting a temperature gradient reference indicative of a spatial temperature gradient in the sensor array in a reference state, particularly at the beginning of a fluid handling procedure. The temperature regulating unit may then be configured, upon detecting that the temperature gradient deviates from the temperature gradient reference over time, to spatially regulate temperature in the sensor array to return the temperature gradient to the temperature gradient reference. Therefore, a reproducible reference state can be defined, for instance a state in which no fluid is supplied to the sensor array (for instance when a pump as a fluid drive unit is switched off). Under these conditions, the thermal pattern indicative of the temperature distribution over at least a part of the sensor array may be measured.

The energy supply to the sensor array may then be configured to keep the system in the reference state over the whole sensor measurement interval. Therefore, reproducible sensor results may be obtained which do not suffer from artifacts resulting from a change of the thermal pattern within the sensor array. During analysis, before the gradient starts, the temperature gradient across the sensor array may be measured. This temperature gradient may be stabilized by at least one heater or cooler. During the solvent gradient the heat transfer changes but is compensated by the heater/cooler. Therefore the gradient is kept constant, and accuracy across the sensor array is maintained.

[0024] In an embodiment, a first flow sensor is arranged in the fluid conduit between a first solvent container and a mixing point. A second flow sensor may be arranged in the fluid conduit between a second solvent container and the mixing point. The mixing point may be configured for mixing first solvent with second solvent. Such a system may be implemented within a pumping system in which a solvent composition is mixed out of two (or more) solvent compositions. In such a scenario, the flow rate in the various channels being indicative of the partial flows relating to the individual solvent components may be measured by the sensor array having two or more of such flow sensors arranged in the various conduits connected to the various solvent containers. Therefore, in such a binary (or other, for instance quaternary) pump, it may be required to correspondingly control the pump accordingly.

[0025 In an embodiment, a third flow sensor (and optionally one or more further flow sensors) is arranged in the fluid conduit downstream of the mixing point. This third flow sensor may at the same time be arranged upstream of a fluid drive unit The third flow sensor may be arranged in a conduit in which the solvent composition mixed from components of the first solvent and the second solvent flows.

[0026] In an embodiment, the temperature gradient detecting unit comprises a first temperature sensor configured for detecting a temperature at a first sensor position in the sensor array, comprises a second temperature sensor configured for detecting a temperature at a second sensor position in the sensor array, and is configured for deriving the temperature gradient data based on a signal of the first temperature sensor, a signal of the second temperature sensor, the first sensor position, and the second sensor position. Therefore, for determining the temperature pattern within the sensor array, two or more thermometers or temperature probes capable of measuring the temperature at a certain spatial position within the sensor array may be provided. These two or more thermometers may then be capable of measuring the pattern of the temperature distribution within the sensor array, either using exclusively their measurement signals or evaluating the measurement signals in combination with further data (such as preknown temperature pattern data indicative of a temperature pattern within the sensor array).

[0027] In an embodiment, the temperature regulating unit comprises a first heating and/or cooling element configured to provide heating and/or cooling energy at a first heating and/or cooling position. Optionally, one or more second heating and/or cooling element may be provided and configured to provide heating and/or cooling energy at a second heating and/or cooling position. As a heating element, it is for instance possible to use an ohmic heater such as a resistor through which an electric current is conducted. Alternatively, a Peltier element may be used which can selectively provide heating energy or cooling energy to the system. Other temperature adjustment systems are implementable as well.

[0028] In an embodiment, at least one of the plurality of flow sensors comprises a first sensor thermometer arranged at a first sensor thermometer position, comprises a second sensor thermometer arranged at a second sensor thermometer position, and comprises a heating and/or cooling entity configured for providing heating and/or cooling energy to the fluid flowing through the fluid conduit within which said flow sensor is arranged. The first sensor thermometer and the second sensor thermometer may be configured for determining the flow of the fluid based on sensor signals determined in response to the provided heating and/or cooling energy. Therefore, two or more thermometers measure a thermal value at a dedicated position within or in thermal contact with the fluidic channel. By selectively supplying a defined amount of thermal energy at a position for instance between these two temperature sensors, the thermal system may be selectively disturbed, i.e. brought out of thermal equilibrium, wherein the change of the sensor signals by the thermometers then allows to calculate the flow rate, since the propagating fluid will carry the supplied thermal energy to the respectively other temperature sensor.

[0029] In an embodiment, the sensor array comprises a casing enclosing the plurality of flow sensors and/or the temperature gradient detecting unit and/or the temperature regulating unit. Enclosing the components of the sensor array into a casing of a material having a poor thermal conductivity allows to shield the components of the sensor array from an environment and to avoid a thermal equilibration within the sensor array. In contrast to this, an existing thermal gradient shall be maintained in embodiments of the invention.

[0030] In an embodiment, the sensor array comprises a substrate, particularly a thermally conductive plate, wherein the plurality of flow sensors, the temperature gradient detecting unit, and temperature regulating unit are arranged on and/or in the substrate. Arranging all the components on and/or integrating them in a plate-like substrate may allow to manufacture the sensor array in a very compact way.

[0031] In an embodiment, the fluid conduit is at least partly arranged over the substrate, particularly within a laminate structure attached to the substrate.

Therefore, a chip-like fluidic conduit structure formed of a laminated array of planar layers (a part of the layers may be patterned) may be arranged on top of the substrate housing the thermal gradient detector unit and the regulating unit.

10032] In an embodiment, at least a part of the plurality of flow sensors is configured for sensing a flow rate in a range between about 1 nI/mm and about 100 p1/mm, particularly in a range between about 10 nI/mm and about 10 p1/mm.

Therefore, the sensor array may be specifically configured for microfluidic or nanofluidic applications. The term "microfluidic" may particularly relate to a fluidic device as described herein which allows to convey fluid through microchannels having a dimension in the order of magnitude of less than 500 pm, particularly less than 200 pm, more particularly less than 100 pm or less than 50 pm or less. The term "nanofluidic" may particularly denote a fluidic device as described herein which allows to convey fluid through nanochannels having even smaller dimensions than the microchannels. In these dimensions, measurement of fluid properties is very difficult and conventional ways of operating a pump may be no more applicable.

Hence, in such a scenario the impact of a thermal distribution within the sensor array is specifically critical for pump control purposes. In the low flow regime of liquid chromatography the flow is controlled with flow sensors. These sensors control in a feedback loop the operation of a pump. If the solvent delivery system has two or more solvent channels, two or more flow sensors may be used. As such sensors are temperature dependent, a temperature stabilization should be used to obtain a high accuracy.

[0033] In an embodiment, the temperature gradient detecting unit is configured for detecting the temperature gradient data by detecting at least two temperature values at at least two positions in the fluidic path upstream of the plurality of flow sensors, wherein the temperature regulating unit is configured to estimate, based on the detected at least two temperature values, a required amount of cooling and/or heating energy to be supplied to at least one position in the sensor array required to stabilize the spatial temperature gradient over time. In this embodiment, the temperature measurement is performed at a position very close to an upstream end of the sensor array at which fluid flows into the sensor array. Therefore, an influence of such a fluid on a temperature at a more downstream position of the sensor array may be predicted based on certain parameters. Therefore, at a very early point of time the future impact on the sensor array may be detected and the corresponding countermeasures for avoiding an undesired change of the temperature gradient pattern within the sensor array may be taken.

[0034] In an embodiment, the temperature regulating unit is configured to estimate the required amount of cooling and/or heating energy based on at least one property of the conducted fluid, reference measurement data, at least one expert rule, and/or at least one natural law. Particularly, the heat capacity of the various fluids may be considered for this control of the energy supply (a positive or negative energy supply). Also information stored in one or more databases may be taken into account which may be the result of phenomenological knowledge from previous analyses or an impact from natural laws or the like. The accuracy of the regulation of the temperature distribution within the sensor array may be high.

[0035] In an embodiment, the temperature gradient detecting unit is configured for detecting the temperature gradient data indicative of the spatial temperature gradient of the fluid passing the plurality of flow sensors within the fluid conduit.

Particularly, the control may be performed in dependency of the thermal distribution within the fluidic channels in which the flow sensors may be integrated. Therefore, a direct impact of the regulation may be possible rendering the effect on the reproducibility of the sensor data high.

[0036] In the following, further exemplary embodiments of the fluid handling system will be explained. However, these embodiments also apply to the sensor array and to the method.

[0037] In an embodiment, the pumping system is a binary pump having a first pump unit and a second pump unit, each having a reciprocatable element configured for reciprocating within a respective pump chamber, to pump a first solvent supplied from a first solvent container via the fluid conduit and to pump a second solvent supplied from a second solvent container via the fluid conduit, wherein the first pump unit is located upstream of a first flow sensor of the plurality of flow sensors and downstream the first solvent container, and the second pump unit is located upstream of a second flow sensor of the plurality of flow sensors and downstream of the second solvent container.. In such a binary pump arrangement with a chromatographic gradient run being possible, the active regulation of the temperature gradient and its constant value over time may be of significant importance, since the variable solvent composition of two or more solvents which may have different values of the heat capacity may involve specific challenges with regard to a time dependent change of the thermal impact on the sensor array.

Therefore, in such a scenario the active regulation of the temperature distribution within the sensor array is of relevance for the chromatographic separation performance. A typical embodiment has the flow sensor after the pump. However, other geometric arrangements are also possible.

[0038] In an embodiment, the fluid handling system is configured as a fluid separation system for separating compounds of a sample fluid in a mobile phase, the mobile phase being constituted by the fluid. The fluid separation system comprises a mobile phase drive as the pumping system, configured to drive the mobile phase through the fluid separation system, and a separation unit, particularly a chromatographic column, configured for separating compounds of the sample fluid in the mobile phase. Such sample separation systems may for instance be chromatographic separation systems or other separation systems such as electrophoresis device. However, in other embodiment, the fluid handling system may be configured as a fluid purification system [0039] In an embodiment, the fluid handling system is configured for supplying, as the mobile phase, a solvent composition of at least two different solvents having different values of heat capacity to the separation unit to perform a gradient run. The temperature regulating unit may then be configured to spatially regulate temperature to stabilize the spatial temperature gradient over time during the gradient run.

However, not only in a gradient mode, but also in an isocratic mode, the regulation of the temperature gradient within the sensor array may ensure a high reliability of sensor results.

[0040] In an embodiment, the fluid handling system is configured as a liquid chromatography apparatus. For instance, the fluid handling system may be a HPLC.

A HPLC may be operated at high pressures of for instance between 800 bar and 1500 bar requiring a specifically precise control of a corresponding pump.

Embodiments of the invention utilize the sensor signals measured by the sensor array as a basis for controlling such a pump pumping the fluid.

[0041] In an embodiment, the mobile phase drive is configured for driving the mobile phase with a flow rate in a range between about 1 nI/mm and about 100 IJI/min, particularly in a range between about 10 nI/mm and about 10 p1/mm.

Particularly at such small flow rates the precise control of the pump system and the maintenance of the temperature gradient over an analysis is highly advantageous.

[0042] The analysis system may be configured as a microfluidic device. The term "microfluidic device" may particularly denote a fluidic device as described herein which allows to convey fluid through microchannels having a dimension in the order of magnitude of less than 500 pm, particularly less than 200 pm, more particularly less than 100 pm or less than 50 pm or less. The analysis system may also be configured as a nanofluidic device. The term "nanofluidic device" may particularly denote a fluidic device as described herein which allows to convey fluid through nanochannels with a flow rate of less than 100 nI/mm, particularly of less than 10 nI/mm. Particularly, the mobile phase drive may be a microfluidic pump, more particularly a nanofluidic pump.

[0043] In an embodiment, a detector is provided which is configured to detect separated compounds of the sample fluid. Such a detector may include a flow cell having an electromagnetic radiation based detection principle.

10044] In an embodiment, a collection unit is provided which is configured to collect separated compounds of the sample fluid. Such a collection unit may be a fractioner collecting the different separated components of the fluidic sample in different vials or fluid containers.

[0045] In an embodiment, a data processing unit is provided which is configured to process data received from the fluid separation system. Such a data processing unit, for instance a microprocessor or a central processing unit (CPU) may ensure that all the components are properly synchronized during a sample separation procedure.

100461 In an embodiment, a degassing apparatus is provided which is configured for degassing the mobile phase. Such a degassing apparatus may remove bubbles from the solvents which can be disturbing for the sample separation procedure.

[0047] Embodiments of the present invention might be embodied based on most conventionally available HPLC systems, such as the Agilent 1200 Series Rapid Resolution LC system or the Agilent 1100 HPLC series (both provided by the -12-applicant Agilent Technologies -see www.agilent.com -which shall be incorporated herein by reference).

[0048] One embodiment comprises a pumping apparatus having a piston for reciprocation in a pump working chamber to compress liquid in the pump working chamber to a high pressure at which compressibility of the liquid becomes noticeable.

[0049] One embodiment comprises two pumping apparatuses coupled either in a serial or parallel manner. In the serial manner, as disclosed in ER 309596 Al, an outlet of the first pumping apparatus is coupled to an inlet of the second pumping apparatus, and an outlet of the second pumping apparatus provides an outlet of the pump. In the parallel manner, an inlet of the first pumping apparatus is coupled to an inlet of the second pumping apparatus, and an outlet of the first pumping apparatus is coupled to an outlet of the second pumping apparatus, thus providing an outlet of the pump. In either case, a liquid outlet of the first pumping apparatus is phase shifted, preferably essentially 180 degrees, with respect to a liquid outlet of the second pumping apparatus, so that only one pumping apparatus is supplying into the system while the other is intaking liquid (for instance from the supply), thus allowing to provide a continuous flow at the output. However, it is clear that also both pumping apparatuses might be operated in parallel (i.e. concurrently), at least during certain transitional phases for instance to provide a smooth(er) transition of the pumping cycles between the pumping apparatuses. The phase shifting might be varied in order to compensate pulsation in the flow of liquid as resulting from the compressibility of the liquid. It is also known to use three piston pumps having about degrees phase shift.

[0050] The separating device preferably comprises a chromatographic column (see for instance http://en.wikipedia.orglwiki/Column chromatography) providing the stationary phase. The column might be a glass or steel tube (for instance with a diameter from 50 pm to 5 mm and a length of 1 cm to 1 m) or a microfluidic column (as disclosed for instance in EP 1577012 or the Agilent 1200 Series HPLC-Chip/MS System provided by the applicant Agilent Technologies, see for instance http://www.chern.agilent.com/Scrits/PDS.asp?IPacie=38308). For example, a slurry can be prepared with a powder of the stationary phase and then poured and pressed into the column. The individual components are retained by the stationary phase differently and separate from each other while they are propagating at different speeds through the column with the eluent. At the end of the column they elute one at a time. During the entire chromatography process the eluent might be also collected in a series of fractions. The stationary phase or adsorbent in column chromatography usually is a solid material. The most common stationary phase for column chromatography is silica gel, followed by alumina. Cellulose powder has often been used in the past. Also possible are ion exchange chromatography, reversed-phase chromatography (RP), affinity chromatography or expanded bed adsorption (EBA). The stationary phases are usually finely ground powders or gels and/or are microporous for an increased surface, though in EBA a fluidized bed is used.

[0051] The mobile phase (or eluent) can be either a pure solvent or a mixture of different solvents. It can be chosen for instance to minimize the retention of the compounds of interest and/or the amount of mobile phase to run the chromatography. The mobile phase can also been chosen so that the different compounds can be separated effectively. The mobile phase might comprise an organic solvent like for instance methanol or acetonitrile, often diluted with water.

For gradient operation water and organic is delivered in separate bottles, from which the gradient pump delivers a programmed blend to the system. Other commonly used solvents may be isopropanol, THF, hexane, ethanol and/or any combination thereof or any combination of these with aforementioned solvents.

[0052] The sample fluid might comprise any type of process liquid, natural sample like juice, body fluids like plasma or it may be the result of a reaction like from a fermentation broth.

[0053] The pressure in the mobile phase might range from 2-200 MPa (20 to 2000 bar), in particular 10-150 MPa (100 to 1500 bar), and more particular 50-1 20 MPa (500 to 1200 bar).

[0054] The HPLC system might further comprise a sampling unit for introducing the sample fluid into the mobile phase stream, a detector for detecting separated compounds of the sample fluid, a fractionating unit for outputting separated -14-compounds of the sample fluid, or any combination thereof. Further details of HPLC system are disclosed with respect to the Agilent 1200 Series Rapid Resolution [C system or the Agilent 1100 HPLC series, both provided by the applicant Agilent Technologies, under www.apilent.com which shall be in cooperated herein by reference.

[0055] Embodiments of the invention can be partly or entirely embodied or supported by one or more suitable software programs, which can be stored on or otherwise provided by any kind of data carrier, and which might be executed in or by any suitable data processing unit. Software programs or routines can be preferably applied in or by the control unit.

BRIEF DESCRIPTION OF DRAWINGS

[0056] Other objects and many of the attendant advantages of embodiments of the present invention will be readily appreciated and become better understood by reference to the following more detailed description of embodiments in connection with the accompanied drawings. Features that are substantially or functionally equal or similar will be referred to by the same reference signs.

[0057] Fig. 1 shows a liquid chromatography sample separation system according to an exemplary embodiment of the invention having an active regulation mechanism for maintaining a temperature gradient within an assigned sensor array constant over time.

[0058] Fig. 2 shows a sensor array according to an exemplary embodiment of the invention.

[0059] Fig. 3 shows the sensor array of Fig. 2 in a state in which a high amount of a solvent with a high heat capacity such as water is introduced in one channel and another solvent is introduced into another channel of the sensor array.

[0060] Fig. 4 shows the formation of another temperature gradient in the presence of another solvent composition when the amount of water has been decreased and the amount of the other solvent has been increased during a chromatographic gradient run.

[0061] Fig. 5 shows a sensor array according to an exemplary embodiment of the invention with a temperature detection and temperature gradient restoration feature.

[0062] Fig. 6 illustrates an example for a constitution of a flow sensor implemented in the sensor array of Fig. 2 to Fig. 5.

[0063] Fig. 7 shows a schematic illustration of a sensor array according to an exemplary embodiment of the invention in which the various components are integrated on and in a thermally conductive plate.

[0064] Fig. 8 shows a thermally conductive plate with a laminate structure on top thereof as a planar and compact sensor array according to an exemplary embodiment of the invention.

[0065] Referring now in greater detail to the drawings, Fig. I depicts a general schematic of a liquid separation system 10. A pump 20 receives a mobile phase from a solvent supply 25, typically via a degasser 27, which degases and thus reduces the amount of dissolved gases in the mobile phase. The mobile phase received from the solvent supply 25 is composed of a first solvent contained in a first solvent container 74 and of a second solvent contained in a second solvent container 76. The pump 20 -as a mobile phase drive -drives the mobile phase through a separating device 30 (such as a chromatographic column) comprising a stationary phase. A sampling unit 40 can be provided between the pump 20 and the separating device 30 in order to subject or add (often referred to as sample introduction) a sample fluid into the mobile phase using a switchable fluid valve 90.

The stationary phase of the separating device 30 is configured for separating compounds of the sample liquid. A detector 50 is provided for detecting separated compounds of the sample fluid. A fractionating unit 60 can be provided for outputting separated compounds of sample fluid.

[0066] While the mobile phase can be comprised of one solvent only, it may also be mixed from plural solvents. Such mixing might be a low pressure mixing and provided upstream of the pump 20, so that the pump 20 already receives and pumps the mixed solvents as the mobile phase. Alternatively, the pump 20 might be comprised of plural individual pumping units, with plural of the pumping units each receiving and pumping a different solvent or mixture, so that the mixing of the mobile phase (as received by the separating device 30) occurs at high pressure und downstream of the pump 20 (or as part thereof). The composition (mixture) of the mobile phase may be kept constant over time, the so called isocratic mode, or varied overtime, the so called gradient mode.

[0067] A data processing unit 70, which can be a conventional PC or workstation, might be coupled (as indicated by the dotted arrows) to one or more of the devices in the liquid separation system 10 in order to receive information and/or control operation. For example, the data processing unit 70 might control operation of the pump 20 (for instance setting control parameters) and receive therefrom information regarding the actual working conditions (such as output pressure, flow rate, etc. at an outlet of the pump). The data processing unit 70 might also control operation of the solvent supply 25 (for instance setting the solvent/s or solvent mixture to be supplied) and/or the degasser 27 (for instance setting control parameters such as vacuum level) and might receive therefrom information regarding the actual working conditions (such as solvent composition supplied over time, flow rate, vacuum level, etc.). The data processing unit 70 might further control operation of the sampling unit 40 (for instance controlling sample injection or synchronization sample injection with operating conditions of the pump 20). The separating device 30 might also be controlled by the data processing unit 70 (for instance selecting a specific flow path or column, setting operation temperature, etc.), and send -in return -information (for instance operating conditions) to the data processing unit 70. Accordingly, the detector 50 might be controlled by the data processing unit 70 (for instance with respect to spectral or wavelength settings, setting time constants, start/stop data acquisition), and send information (for instance about the detected sample compounds) to the data processing unit 70. The data processing unit 70 might also control operation of the fractionating unit 60 (for instance in conjunction with data received from the detector 50) and provides data back.

[0068] In the following, the detail of the pump 20 and the portion of the liquid chromatography system 10 upstream of the pump 20 will be described in further detail.

[0069] The first solvent container 74 includes a solvent A such as water. A second solvent container 76 includes another solvent B, particularly an organic solvent such as acetonitrile (ACN). Fluid conduits 88 such as capillaries conduct the respective solvents through the fluidic system of Fig. 1. A first heating and/or cooling unit 99 is arranged in a fluidic path between the first solvent container 74 and a first flow sensor 82, wherein a first pump unit 64 comprising a piston reciprocating in a pumping chamber is arranged between the first solvent container 74 and the first heating and/or cooling unit 99. Correspondingly, a second heating and/or cooling unit 97 is arranged in a fluidic path between the second solvent container 76 and a second flow sensor 84, wherein a second pump unit 65 comprising another piston reciprocating in another pumping chamber is arranged between the second solvent container 76 and the second heating and/or cooling unit 97. A first temperature sensor 94 is arranged between the first heating and/or cooling unit 99 and the flow sensor 82 and upstream of a mixing unit 78 for mixing the first solvent with the second solvent. Correspondingly, a second temperature sensor 96 is arranged between the second heating and/or cooling unit 97 and the second flow sensor 84 and upstream of the mixing unit 78. Downstream of the mixing unit 78, the solvent composiflon is guided through a third flow sensor 86 capable of determining the flow of the solvent composition. Downstream of the third flow sensor 86, the solvent composition is guided through a third temperature sensor 83 and subsequently through a third heating and/or cooling unit 44. Reference numeral 80 denotes all the components forming parts of a sensor array according to an exemplary embodiment of the invention.

[0070] Apart from the mentioned components, there is also a temperature gradient detecting unit 92 which is configured for detecting the temperature gradient data indicative of a spatial temperature gradient in the sensor array 80, and a temperature regulating unit 98 configured to spatially regulate temperature in the sensor array 80 in response to the detected temperature gradient data to thereby stabilize the spatial temperature gradient over time. In other words, the temperature sensing data of the temperature sensors 94, 96, 83 are supplied to the temperature gradient detecting unit 92 which derives from these temperature values information indicative of the temperature pattern, distribution or gradient over the spatial extension of the sensor array 80. In order to maintain a once measured reference temperature profile constant over a measurement cycle, the temperature regulating unit 98 uses the output data of the temperature gradient detecting unit 92 and calculates a necessary spatially dependent thermal energy input by the heating and/or cooling units 97, 99, 44 so as to keep the gradient constant over the entire measurement time. Upon detecting a deviation between an actual temperature gradient pattern and a reference pattern which shall be maintained constant, the temperature regulating unit 98 will modify supply of the thermal energy to the system so as to return the system into the target position.

[0071] A pump control unit 66 is capable of controlling operation of the pump units 64, 65, particularly to control operation of the performance of the reciprocating pistons based on the flow values which are determined by flow sensors 82, 84 and 86. In view of the temperature gradient stabilization feature of an embodiment of the invention, the sensor results and the flow sensors 82, 84, 86 are highly reliable.

[0072] As indicated by a dashed line in Fig. 1, all components within the sensor array 80 may be integrated within a casing 75 (which may be poorly thermally conductive) enclosing all these components.

[0073] Fig. 2 shows a schematic view of a flow sensor module. In this example, two channels (A, B) and two flow sensors (not shown) are assumed. Channel C is the outlet.

[0074] Fig. 3 shows a schematic of the heat flow in the flow sensor module of Fig. 2. Channel A has a high flow of solvent with high heat capacity. The solvent is cooler than the device. A larger amount of heat is taken out of the sensor array 80.

The left side of the sensor array 80 cools down. A gradient is imposed on the device.

The shorter arrows 300 symbolize heat transfer from the module in which the sensor array 80 resides. Fig. 3 shows that a temperature gradient may be present in the sensor array 80 when solvents A and B are conducted through the system. By measuring the temperature at different positions, a reference temperature gradient may be determined.

[0075] Fig. 4 shows the situation further along the solvent gradient. Channel A has reduced flow and therefore the heat transfer. Channel B has now a higher flow. In this example the heat capacity of solvent in channel B is assumed to be small. Thus the resulting temperature gradient is small. The smaller temperature gradient causes a shift in sensor signal which is not desired. Fig. 4 shows a scenario in which the fluid composition has changed again as compared to Fig. 3.

[0076] Fig. 5 shows the situation with an embodiment of the invention in place.

An additional arrow 500 on the left symbolizes a Peltier element cooling the sensor array 80 on the left side. The cooling is adjusted to match the situation in Fig. 3, i.e. to manipulate the system so that the present temperature gradient is brought in accordance with the reference temperature gradient. The original temperature gradient is restored. The sensor array 80 will hence show the same sensor sensitivity as in Fig. 3. For instance on a left-hand side, the temperature may be detected at two or more different positions.

[0077] Fig. 6 shows schematically how a flow sensor such as the flow sensor 82 can be constituted according to an exemplary embodiment of the invention.

However, the other flow sensors 84, 86 can also be implemented as shown in Fig. 6 or in a different manner. Fig. 6 shows a fluidic conduit 88 through which a fluid flows. A parabolic or other fluid profile 706 may be formed within the tubular fluid conduit 88 due to friction effects or the like. A fluid flow direction is denoted with reference numeral 708. At a first position within the fluidic conduit 88, a first temperature sensor 700 is provided for detecting the fluid temperature here. Further downstream1 a second temperature sensor 702 is provided for detecting the fluid temperature there. Between the temperature sensors 700, 702, a heating unit 704 is provided for supplying a defined amount of heat to the fluid in the conduit 88. Upon activating the heating unit 704 a thermal energy supply pattern denoted with reference numeral 710 is formed within the conducted fluid. A time-dependence of the change of the signal of the temperature sensors 700, 702 will then allow to calculate the flow of the fluid. The larger the flow, the faster will be the transfer of the additional thermal energy suppfled by the heating unit 704 to the downstream temperature sensor 702.

[0078] Fig. 7 shows an arrangement similar to Fig. 1, wherein all the components, i.e. the flow sensors 82, 84, 86, the heating units 99, 97 and the fluidic conduits 88 are integrated within a substrate 900 such as a metal plate. When temperature sensors 94, 96 have detected a certain temperature gradient pattern, -20 -any change of this pattern over time will trigger activation of the heating units 99, 97 so as to compensate for the changes and to bring back the sensor array into the reference state with regard to a thermal distribution pattern within the sensor array.

[0079] Fig. 8 shows a metal plate 900 having modules 904 integrated therein in a top surface thereof. In a core of these modules 904, a corresponding flow sensor 82, 84 or 86 is provided. The fluidic channels 88 (only schematically illustrated in Fig. 8) are integrated in a laminate structure 902 of polyimide or metal layers laminated together and having internal fluidic structures formed by grooves or the like in the various layers. Moreover, combined temperature sensing and temperature manipulating units 906, 908 are provided at or in the substrate 900 which are capable of measuring a temperature gradient pattern within the plate 900 and, in case of a change, supply thermal energy so as to compensate for these changes.

[0080] It should be noted that the term "comprising" does not exclude other elements or features and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims. -21 -

Claims

<claim-text>CLAIMS1. A sensor array (80) for a fluid handling system (10) for handling a fluid, the sensor array (80) comprising: a plurality of flow sensors (82, 84, 86) each configured for detecting data indicative of a flow of the fluid; a fluid conduit (88) in fluid communication with the plurality of flow sensors (82, 84, 86) and configured for conducting the fluid; a temperature gradient detecting unit (92) configured for detecting temperature gradient data indicative of a spatial temperature gradient in the sensor array (80); a temperature regulating unit (98) configured to spatially regulate temperature in the sensor array (80) in response to the detected temperature gradient data to thereby stabilize the spatial temperature gradient over time.</claim-text> <claim-text>2. The sensor array (80) of claim 1, wherein the temperature regulating unit (98) is configured to spatially regulate temperature in the sensor array (80) to thereby maintain the spatial temperature gradient constant over time.</claim-text> <claim-text>3. The sensor array (80) of claim 1 or 2, wherein the temperature gradient detecting unit (92) is configured for detecting a temperature gradient reference indicative of a spatial temperature gradient in the sensor array (80) in a reference state, particularly at the beginning of a fluid handling procedure or while a pumping unit (20) for pumping the fluid is switched off; wherein the temperature regulating unit (98)is configured, upon detecting that the temperature gradient deviates from the temperature gradient reference over time, to spatially regulate temperature in the sensor array (80) to return the temperature gradient towards the temperature gradient reference.</claim-text> <claim-text>4. The sensor array (80) of any of claims 1 to 3, wherein a first flow sensor (82) is arranged in the fluid conduit (88) between a first solvent container (74) and a -22 -mixing paint (78), and wherein a second flow sensor (84) is arranged in the fluid conduit (88) between a second solvent container (76) and the mixing point (78), the mixing point (78) being configured for mixing first solvent with second solvent.</claim-text> <claim-text>5. The sensor array (80) of claim 4, wherein a third flow sensor (86) is arranged in the fluid conduit (88) downstream of the mixing point (78).</claim-text> <claim-text>6. The sensor array (80) of any of claims 1 to 5, wherein the temperature gradient detecting unit (92) comprises a first temperature sensor (94) configured for detecting a temperature at a first sensor position in the sensor array (80), comprises a second temperature sensor (96) configured for detecting a temperature at a second sensor position in the sensor array (80), and comprises a determining unit (92) configured for deriving the temperature gradient data based on a signal of the first temperature sensor (94), a signal of the second temperature sensor (96), the first sensor position, and the second sensor position.</claim-text> <claim-text>7. The sensor array (80) of any of claims 1 to 6, wherein the temperature regulating unit (98) comprises a first heating and/or cooling element (99) configured to provide heating and/or cooling energy at a first heating and/or cooling position, and optionally comprises a second heating and/or cooling element (97) configured to provide heating and/or cooling energy at a second heating and/or cooling position.</claim-text> <claim-text>8. The sensor array (80) of any of claims 1 to 7, wherein at least one of the plurality of flow sensors (82, 84, 86) comprises a first sensor thermometer (700) arranged at a first sensor thermometer position, comprises a second sensor thermometer (702) arranged at a second sensor thermometer position, and comprises a heating and/or cooling entity (704) configured for providing heating and/or cooling energy to the fluid flowing through the fluid conduit (88) at which said flow sensor (82, 84, 36) is arranged, wherein the first sensor thermometer (700) and the second sensor thermometer (702) are configured for determining the flow of the fluid based on sensor signals determined in response to the provided heating and/or cooling energy.</claim-text> <claim-text>-23 - 9. The sensor array (80) of any of claims 1 to 8, comprising a casing (75) enclosing at least part of a group consisting of the plurality of flow sensors (82, 84, 86), the temperature gradient detecting unit (92), and the temperature regulating unit (98).</claim-text> <claim-text>10. The sensor array (80) of any of claims 1 to 9, comprising a substrate (900), particularly a thermally conductive plate, wherein the plurality of flow sensors (82, 84, 86), the temperature gradient detecting unit (92), and temperature regulating unit (98) are arranged on and/or in the substrate (900).</claim-text> <claim-text>11. The sensor array (80) of claim 10, wherein the fluid conduit (88) is at least partly arranged over the substrate (900), particularly within a laminate structure (902) attached to the substrate (900).</claim-text> <claim-text>12. The sensor array (80) of any of claims 1 to 11, wherein at least a part of the plurality of flow sensors (82, 84, 86) is configured for sensing a flow rate in a range between 1 nI/mm and 100 p1/mm, particularly in a range between 10 nI/mm and 10 p1/mm.</claim-text> <claim-text>13. The sensor array (80) of any of claims ito 12, wherein the temperature gradient detecting unit (92) is configured for detecting the temperature gradient data by detecting at least two temperature values at at least two positions in the fluidic path upstream of the plurality of flow sensors (82, 84, 86); wherein the temperature regulating unit (98) is configured to estimate, based on the detected at least two temperature values, a required amount of cooling and/or heating energy to be supplied to at least one position in the sensor array (80) required to stabilize the spatial temperature gradient over time.</claim-text> <claim-text>14. The sensor array (80) of claim 13, wherein the temperature regulating unit (98) is configured to estimate the required amount of cooling and/or heating energy based on at least one of the group consisting of at least one property of the conducted fluid, reference measurement data, at least one expert rule, and at least one natural law.</claim-text> <claim-text>-24 - 15. The sensor array (80) of any of claims 1 to 14, wherein the temperature gradient detecting unit (92) is configured for detecting the temperature gradient data indicative of the spatial temperature gradient in the fluid passing the plurality of flow sensors (82, 84, 86) within the fluid conduit (88).</claim-text> <claim-text>16. A fluid handling system (10) for handling a fluid, the fluid handling system (10) comprising: a sensor array (80) of any of claims 1 to 15; a pumping system (20) configured to drive the fluid through the fluid handling system (10); a drive unit (66) configured for driving the pumping system (20) based on the data detected by the sensor array (80) and being indicative of the flow of the fluid.</claim-text> <claim-text>17. The fluid handling system (10) of claim 16, wherein the pumping system (20) is a binary pump having a first pump unit (64) and a second pump unit (65), each having a reciprocatable element configured for reciprocating within a respective pump chamber, to pump a first solvent supplied from a first solvent container (74) via the fluid conduit (88) and to pump a second solvent supplied from a second solvent container (76) via the fluid conduit (88), wherein the first pump unit (64) is located upstream of a first flow sensor (82) of the plurality of flow sensors (82, 84, 86) and downstream the first solvent container (74), and the second pump unit (65) is located upstream of a second flow sensor (84) of the plurality of flow sensors (82, 84, 86) and downstream of the second solvent container (76).</claim-text> <claim-text>18. The fluid handling system (10) of claim 16 or 17, configured as a fluid separation system (10) for separating compounds of a sample fluid in a mobile phase, the mobile phase being constituted by the fluid, the fluid separation system comprising: a mobile phase drive (20) as the pumping system, configured to drive the mobile phase through the fluid separation system (10); and -25 -a separation unit (30), particularly a chromatographic column, configured for separating compounds of the sample fluid in the mobile phase.</claim-text> <claim-text>19. The fluid handling system (10) of any of claims 18, configured for supplying, as the mobile phase, a solvent composition of at least two different solvents having different values of heat capacity to the separation unit (30) to perform a gradient run, wherein the temperature regulating unit (98) is configured to spatially regulate temperature to stabilize the spatial temperature gradient over time during the gradient run.</claim-text> <claim-text>20. The fluid handling system (10) of claim 18 or 19, further comprising at least one of: the fluid handling system (10) is configured as a liquid chromatography apparatus; the mobile phase drive (20) is configured for driving the mobile phase with a flow rate in a range between 1 nI/mm and 100 p1/mm, particularly in a range between 10 nI/mm and 10 p1/mm; the mobile phase drive (20) is a microfluidic pump; the mobile phase drive (20) is a nanofluidic pump; a detector (50) configured to detect separated compounds of the sample fluid; a collection unit (60) configured to collect separated compounds of the sample fluid; a data processing unit (70) configured to process data received from the fluid separation system (10); a degassing apparatus (27) for degassing the mobile phase.</claim-text> <claim-text>21. A method of handling a fluid using a sensor array (80), the method comprising: detecting data indicative of a flow of the fluid by a plurality of flow sensors (82, 84, 86) of the sensor array (80), the fluid being conducted through a fluid conduit (88) in fluid communication with the plurality of flow sensors (82, 84, -26 -86); detecting temperature gradient data indicative of a spatial temperature gradient in the sensor array (80); spatially regulating temperature in the sensor array (80) in response to the detected temperature gradient data to thereby stabilize the spatial temperature gradient over time.-27 -</claim-text>