• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention is carried out by a volumetric displacement calibration device (1) comprising an opening (18) configured to adapt a suction system, preferably a pipette. The volumetric displacement calibration device (1) comprises at least a first chamber (12) having a volume V 00 and at least one reference chamber (10), having a volume V ref, connected to said first chamber (12) by a first conduit (14). A first valve (16) is disposed on said first conduit (14) and is switchable from an open position. At least one pressure sensor (20) connected to said first chamber (12). The invention is also carried out by a calibration process for calibrating the volume of aspirated substances such as liquids. The invention also relates to a displacement displacement calibration system (2) and the use of the device for measuring the leakage of a suction system device (100).
    公开号:CH715253A2
    申请号:CH00929/19
    申请日:2019-07-22
    公开日:2020-02-14
    发明作者:Bonzon David；Bertrand Daniel
    申请人:Unipix Sarl；
    IPC主号:
    专利说明:

    Description Technical Field [0001] The invention relates to the field of handling liquid and solid substances, in particular a method for calibrating aspirated volumes of liquids and / or solid substances.
    The invention also relates to a volume calibration device and a system configured to calibrate the volume of aspirated substances, such as liquids, and a system suitable for carrying out the process.
    State of the art The precise measurement of the volume of liquid sucked in and / or distributed, gaseous or solid substances is important in several fields, in particular in those of chemistry and biology in which the volumes sucked are the mostly small, usually less than 1000 ft. Current standard calibration methods for laboratory liquid aspirators, such as pipettes, are primarily based on a gravimetric method, which involves the precise measurement of the weight of the liquid delivered with a precision laboratory balance. The majority of pipettes on the market have a maximum displacement range of between 10 μΙ and 1000 μΙ. The most common categories are 10 μΙ, 20 μΙ, 100 μΙ, 200 μΙ and 1000 μΙ.
    Alternatively, the calibration of the liquid dispenser can be carried out according to the principle of dilution of a colored or fluorescent solution in a known volume of water. Dilution methods require the use of well-characterized test solutions and precise knowledge of the volume of solvent sample. It also requires a very precise optical detection device which itself requires regular calibration.
    The specifications of laboratory devices for handling liquids, such as pipettes, are guided by ISO standard 8655. This standard imposes a systematic error typically less than 1% of the displacement and a random error less than 0.4 % for the maximum range of the pipette. These error values may be higher for small volumes. The precision required for the measurement of the volumetric displacement is of the order of 0.1 μΙ. This requires (for the density of water), an accuracy of 0.1 mg in the weighing of the substance, typically a liquid. The calibration process requires: 1) a precise balance, 2) compensation for temperature errors, 3) avoiding evaporation of the liquid and 4) a series of very meticulous manipulations.
    [0006] Users of laboratory pipettes, according to their precision constraints, must regularly check and calibrate their pipettes. As calibrations require specific skills, users often outsource this task to external service providers. The cost of calibration is therefore a significant part of the cost of operating laboratory pipettes.
    There are no simple and economical pipette calibrators on the market and none have been disclosed in prior art documents. The majority of existing or described products are based on laboratory scales and require very meticulous handling and weighing of liquids. There are at least two products called “pipette testers” based on the measurement of the leak rate when the pipette is under pressure and which are described in the following Internet references 1-2:
    1) https://www.brandtech.com/product/plt-pipette-leak-testing-unit/
    2) https://www.aandd.jp/products/test_measuring/pipette/adl690.html [0008] Checking for leaks rejects leaking pipettes, but is not a measure of volumetric accuracy, as required by ISO 8655. Therefore, the gravimetric calibration process is still necessary to approve the pipettes.
    Document US 2012/0 240 663 describes a method for testing the tightness of manual piston pipettes and an associated tightness control device. The system and method described in US 2012/0 240 663 can detect leaks in single-channel and multi-channel piston pipettes using a pressure sensor and a vacuum pump and involves measuring the elevation pressure after stopping or disconnecting the vacuum pump, the system and method do not provide a solution to accurately measure the volumes drawn up by the pipettes.
    Document US 3,962,916 describes a complicated system comprising a plurality of electronically controlled fluid valves for measuring a closed air space, but would not be suitable for accurately calibrating a small volume of a liquid sucked. It is based on the use of a regulated gas supply, necessary to generate a reference pressure.
    Document US 8,561,459 describes a volume gauge comprising a chamber comprising a pressure change device coupled to said chamber. The pressure change device is configured to change a pressure and to measure the pressure of the air in the room. A processor having, stored in a memory, the total volume of the chamber and a reference pressure corresponding to an empty chamber is used. Based on the pressure measurement data received, the processor can determine the percentage of volume occupied by a
    CH 715 253 A2 solid or liquid substance. Although the system described in document US 2012/0 240 663 makes it possible to approximately determine the volume of a solid or liquid substance, the system is not very fast and is not precise and can at best achieve a precision of 'about 1%. In addition, the system is complex because it requires a pressure control system. In addition, in order to obtain higher precision, the system of US 2012/0 240 663 would require a correction to compensate for temperature variations. In addition, evaporation of the liquid can be an additional source of inaccuracy.
    Therefore, we need a better system than those available in the prior art. The system will have to be simpler, cheaper, faster and more reliable than existing systems. In addition, the accuracy should be at least as good or better than the accuracy of the gravimetric liquid measurement method, which is the reference method used in the ISO Standard. In addition, a new system is required so that the user can easily perform a calibration as often as desired without the need for an accurate balance and possibly without liquid or sample solution. A new method and a new system will have to reduce the operating costs of laboratory pipettes and improve quality control thanks to its ease of use. None of the above requirements can be met by existing precision volume measurement systems.
    权利要求:
    Claims (15)
    [1]
    Summary of the Invention The invention provides a new method for calibrating a liquid handler and a system, configured to calibrate the volume of aspirated and / or dispensed substances, such as liquids, which provide solutions to the limitations prior art calibration devices and methods. The calibration method and device does not require handling of a liquid sample and is based on the measurement of the volume of air movement by the change of pressure within a closed volume. The available barometric pressure sensors have an absolute accuracy of less than 0.1 mbar and a short-term repeatability of less than 0.02 mbar. Since the relative change in pressure is equal to the volume of relative change, a typical absolute accuracy of 0.1% can be obtained on displacement measurements.
    The calibration procedure by measuring the air volume is at least as precise as the existing gravimetric methods, but it is much simpler and much faster and less expensive. In addition, there is no need to compensate for the effects of the temperature change and the system does not require evaporation to be avoided. Unlike known gravimetric calibration techniques, the user can easily perform the calibration as often as desired without the need for an accurate balance. In addition, since the system does not use any liquid, the user can check the functionality of the pipette and its tip before a given measurement. The new process of the invention, for example, reduces the cost of operating laboratory pipettes and improves quality control due to its ease of use. In addition, the method allows for example the detection and characterization of faults in dispensing devices and the need to replace the seal in the liquid handling device such as pipetting devices.
    More specifically, the invention is carried out by a volumetric calibration process of a fluid handling system comprising the steps (a-i) consisting in:
    a) provide a system configured to aspirate and / or dispense liquid or solid substances, such as a pipette;
    b) providing a volumetric displacement calibration device comprising a first chamber having a volume V O o and a reference chamber, having a reference volume V re f, connected to said first chamber by a first conduit on which is placed a first valve, said valve being configured to be switched from an open position, allowing said first chamber and said reference chamber to be in fluid communication, to a closed position so that said first chamber and the reference chamber do not are not in fluid communication, said first chamber comprising at least one pressure sensor;
    c) connect said suction / distribution system to said first chamber while said first valve is in said open position;
    d) measuring an initial pressure in said first chamber using said pressure sensor;
    e) activating the suction / distribution system from a first reference volume position R1 to a second predetermined positive or negative reference volume position R2, said first and second reference positions R1, R2 defining a displaced volume AV;
    f) measuring an intermediate pressure Pj in said first chamber using said pressure sensor while the pipette remains in said second position R2 of predetermined volume;
    CH 715 253 A2
    g) switching said first valve from said closed position to said open position so that said first chamber and said reference chamber both reach a final pressure P 2 ;
    h) measuring said final pressure P 2 using said pressure sensor;
    i) determine the value of said displaced volume AV using the values of said initial, intermediate and final pressures P 1f P 2 , by applying the following relation:
    AV = V ref / (Pi / (Pi - Po) - P2 / P2 - Po)) In one embodiment, the method comprises a step of connecting the first chamber to at least one second chamber predetermined by a second conduit comprising a second valve, by positioning said second valve in its open position.
    In one embodiment, the method comprises a step of connecting the first chamber to at least a second predetermined chamber by a second conduit comprising a second valve, by positioning said second valve in its open position.
    In one embodiment, said suction / distribution system is a pipette, preferably comprising a pipette tip, and the method comprises, before the steps aj for measuring the volume an additional step of selecting the size of the pipette tip.
    In one embodiment, said volumetric displacement calibration device comprises a step of adapting the size and / or the shape of the fluid communication of said suction system to said device according to a predetermined size of the suction opening (O) of said suction system.
    In one embodiment, the volumetric displacement calibration device comprises a fluid communication of a predetermined selection of chambers to form a first chamber and / or the fluid communication of another predetermined selection of chambers to form a reference chamber.
    The invention is also carried out by a volumetric displacement calibration device comprising at least one opening configured to adapt a suction system, preferably a pipette, and in which
    - Said displacement displacement calibration device comprises at least a first chamber having a volume Voo and at least one reference chamber, having a volume V re f, connected to said first chamber by a first conduit;
    - A first valve arranged on said first conduit and configured to be switchable from an open position, allowing said first chamber and said reference chamber to be in fluid communication, in a closed position in which said first and second chambers are not not in fluid communication,
    - at least one pressure sensor connected to said first chamber.
    In one embodiment, said first chamber comprises at least two fluid chambers in fluid communication using a conduit comprising a valve. In a variant, said first chamber has a continuously variable volume.
    In one embodiment, said reference chamber comprises at least two chambers in fluid communication thanks to a conduit comprising a valve. In a variant, said reference chamber has a variable volume.
    In one embodiment, said opening is a configurable opening whose size and / or shape can be adapted according to a predetermined size and / or shape.
    In one embodiment, at least part of said chamber is made at least partially with MEMS technology.
    In one embodiment, said device is made at least partially from glass. In an advantageous embodiment, said device is a monolithic device.
    In one embodiment, the volume defined by the chamber of a suction system and said first chamber is less than 6 times the volume moved from the displacement displacement calibration device in operation.
    The invention also relates to a volumetric displacement calibration system comprising the volumetric displacement calibration device and comprising a computer for calculating the displaced volume according to the method described. The invention also relates to the use of the volumetric displacement calibration device; configured to measure the leakage of a suction device such as a pipetting device.
    Brief description of the drawings [0029] Additional details of the invention will appear more clearly on reading the following description with reference to the appended figures:
    fig. 1a, 1b
    CH 715 253 A2
    schematically represent a cross section of a calibration device of a liquid manipulator; fig. 2 illustrates a liquid handler calibration system; fig. 3 illustrates the use of a pipette calibration system; fig. 4a to 4f represent different steps of a pipette calibration sequence by a volumetric displacement calibration device of the invention; fig. 5a-5c illustrate embodiments of volumetric displacement calibration devices comprising a plurality of chambers which can be implemented either in parallel or in series, as illustrated in this figure; fig. 6a and 6b illustrate, respectively, the use of a displacement displacement calibration device to detect leaks in a pipette and leaks at a pipette tip; fig. 7a shows a 3D view of a monolithic liquid handling calibration device and a system comprising a movable plate having a plurality of openings; fig. 7b shows a cross section of two joined parts of a monolithic liquid handling device. Figs. 8 to 11 show the experimental results obtained with a calibration device of the invention; fig. 12 shows experimental results for determining measurement accuracy based on the volume involved in a liquid handling device. Fig. 13 shows comparison measurements between a gravimetric method and the method and device of the invention.
    Detailed description and embodiments of the invention The present invention will be described with reference to particular embodiments and with reference to certain drawings, but the invention is not limited to these. The drawings described are only schematic and are not limiting. In the drawings, the size of some items may be exaggerated and may not be drawn to scale for illustration purposes. The dimensions and the relative dimensions do not correspond to the reality of the reductions in the practice of the invention.
    It should be noted that the term "comprising" in the description and the claims should not be interpreted as being limited to the means listed below, that is to say that it does not exclude other elements.
    The reference throughout the description to "an embodiment" means that a feature, structure or characteristic described in relation to the embodiment is included in at least one embodiment of the invention. Thus, the expressions “in an embodiment” or “in a variant”, at various places in the description, do not necessarily all refer to the same embodiment, but to several. In addition, the particular properties, structures or characteristics can be combined in any suitable way, as will easily be understood by a person skilled in the art, in one or more embodiments. Likewise, various properties of the invention are sometimes grouped together in a single embodiment, figure or description, with the aim of facilitating the reading of the disclosure and improving its understanding of one or more of the different aspects. inventive. In addition, while certain embodiments described below include certain properties but not other properties included in other embodiments, the combinations of properties in different embodiments are intended to comply with the scope of the invention. , and from different embodiments. For example, one of the claimed embodiments can be used in any combination. It is also understood that the invention can be put into practice without some of the many specific details stated. In other cases, all the structures are not shown in detail so as not to affect the understanding of the description and / or the figures.
    The invention is carried out by a liquid handling device 1, also defined as being a liquid handling calibration device or volumetric displacement calibration device. The invention is carried out by a liquid manipulator calibration system 1 and a liquid handling system calibration method 100 which can be a suction system and / or a distribution system. In this document, the term system or device means that the system can also be a delivery system and can be a system that is configured to aspirate and deliver substances such as liquids. It is understood that the device 1 of the invention can be configured to handle liquids or solids or liquids comprising solid substances. In preferred embodiments, the liquid manipulator calibration device 1 is a pipette calibration apparatus for pipettes 100 with or without a plunger. The handling system calibration device
    CH 715 253 A2 liquids 1 of the invention relates to the handling, such as suction and transfer, of substances preferably having small volumes of less than 10 ml. Larger volumes such as 100 ml can be used depending on the volumes of the chambers 10, 12 of the device 1 as described below. The handling of liquids is defined here in broad outline and is not necessarily limited to liquids, but it can also be the handling of gels, powders and mixtures of liquid and solid substances.
    Figs. 1a, 1b and figs. 3a to 3f illustrate an embodiment of a volumetric displacement calibration device 1 comprising at least one opening 18 configured to adapt the inlet opening EA of a suction system 100, preferably the nozzle 100 'of a pipette 100, and where:
    - Said liquid manipulator calibration device 1 comprises at least a first chamber 12 having a volume Voo and a reference chamber 10, having a volume V re f, connected to said first chamber 12 by a first conduit 14;
    - A first valve 16 is disposed on said first conduit 14 and configured to be switchable from an open position, allowing said first chamber 12 and said reference chamber 10 to be in fluid communication, to a closed position in which said first 12 and second chambers 10 are not in fluid communication;
    - at least one pressure sensor 20 connected to said first chamber 12.
    Said first conduit 14 and said chambers 10,12 can be made of the same material or different materials. The preferred materials for the liquid handling system calibration device 1 are metals, ceramics, semiconductors or plastics or a combination thereof. Said valve 16 can consist of different types of valves such as manual mechanical valves or electromagnetic valves or microvalves integrated in the liquid manipulator calibration device 1 using micro-technologies. It is also understood that a valve may include several identical or different valves arranged on the same conduit or at the inlet and / or outlet openings of the corresponding chambers 10, 12.
    The suction system 100 comprises a suction element 110 and at least one suction chamber 101 having a suction or distribution volume V p when the suction system 100 is positioned in an initial position, defined as a first reference position R1 as illustrated in the embodiment linked to the use of a pipette 100 of FIGS. 3d-3rd. It is understood that said suction element 110 can be any element or part of an element which undergoes displacement or deformation. For example, the displacement element can be the piston of a pipette, but can also be the deformation of a surface of a part of a suction system, such as changing the curvature of a wall flexible liquid container.
    An initial volume V o is defined as being the sum of said suction or distribution volume V p and the volume Vqo, ie V o = V p + Voo · In the case of a suction system 100 such than a pipette 100, said initial volume V o comprises the volume of the reservoir 101 of the pipette 100 and the volume 103 of the nozzle 100 'of the pipette. It is also understood that a suction system can comprise more than one suction / distribution tank 101. In embodiments, several openings can be arranged in the device 1 so that a nozzle can be placed on a single device 1.
    As explained later in the experimental section, said suction volume V p must not be too large relative to the volume AV of movement d of the suction element 110 during calibration. Typically, V p should be less than 15 x AV, preferably less than 10 x AV, preferably less than 6 x AV.
    The liquid manipulator calibration device 1 comprises means for fixing the suction end of a suction / distribution device, such as the tip 100 ′ of a pipette 100. As explained more in detail in the process section and illustrated in figs. 3a to 3f, for calibration, the suction device, preferably a pipette, is configured so that a user activates the suction device 100 for a defined volumetric displacement AV to be measured. As illustrated in fig.4b-4c, the device provides a pressure P o (fig. 4c) before the displacement and Pj after the compression of the air due to the displacement (fig. 4d). As the initial test volume is not known, the device has a second cavity having a defined volume V re f which is used as a reference. The second cavity is defined as the reference chamber 10. As explained further in the process section, the displacement volume AV can be calculated from the measurements of the pressure P o before application of the displacement, the pressure Pi after application of the displacement of AV and of the pressure P 2 after opening the valve 16 towards the reference cavity 10.
    The air calibration process is as precise as the liquid gravimetric method, but much simpler, requiring no liquid, and much faster. In addition, there is no need to compensate for the temperature or avoid evaporation. Unlike the gravimetric calibration method, the user can easily perform the calibration as often as desired without the need for a precision balance. This new process, device 1 and system 2, reduce the operating cost of laboratory liquid handlers such as pipettes and improves quality control due to its ease of use. In addition, this method makes it possible to detect and characterize, for example, faults in pipetting devices or the need to replace the seal in suction devices such as pipetting devices.
    In one embodiment, at least one additional chamber is connected to said first chamber 12 by a second conduit comprising a second valve.
    CH 715 253 A2 In a variant, at least one other chamber is connected to said first chamber by a third conduit comprising a third valve.
    In advantageous embodiments illustrated in FIGS. 4a to 4c, a plurality of chambers can be arranged in fluid communication with said first chamber 12 and / or a plurality of chambers can be arranged in fluid communication with said reference chamber 10. In embodiments said chambers can be connected in series (fig. 4a, 4c) and / or in parallel (not shown in the figures). As described below, the chambers can be arranged in different ways on parallel planes.
    The advantages of using several chambers which can be placed in fluid communication with a first chamber and / or a reference chamber is to be able to provide a first reconfigured chamber 12 and / or a reconfigured reference chamber 10 having different volumes predetermined according to the selection of some of said connectable chambers according, for example, to the use of a particular liquid handling device.
    For example, FIG. 5a illustrates this in an example configuration in which three chambers having volumes of V O o, V O i and f 02 are in fluid communication and form a first chamber 12. A valve separates this first chamber 12 from a reference comprising three chambers in fluid communication and having volumes of V re f, V re f, i and V re f, 2 · [0046] FIG. 5b illustrates another embodiment in which the first formed chamber 12 has a volume V o = V p + Voo + Voi and in which is formed a reference chamber 10 having a volume V re f = V re f, o + V re f, i.
    [0047] FIG. 5b illustrates another advantageous embodiment in which the first chamber 12 has a volume V o = Vp + Voo θί in which a reference chamber 10 is formed having a volume V re f = V re f, o · [0048] In closing or opening the valves 16, 16 ', 16, 16 a wide variety of first chambers 12 and reference chambers 10 can be provided.
    It is understood that, in embodiments, said chambers can be a plurality of micro-chambers such that said first chamber 12 and / or said reference chamber 10 can comprise a large number of micro-chambers, for example more than 10, preferably more than 100 micro-chambers connected by microfluidic channels, some of which include micro-valves or even nanovalves. As a variant, the micro-chambers can have dimensions of less than 20 μm x 20 μm x 10 μm.
    In an advantageous embodiment of the invention, instead of using several fluidically connected chambers, the device 1 can comprise at least one chamber 10,12 which has a variable volume, such as a chamber whose the volume can be modified by deformation or by using a piston or any other means. The use of such a chamber is described in detail in one embodiment of the method. Such a variant requires the use of a precise and calibrated piston or deformation system.
    In one embodiment, the volumetric displacement calibration device 1 comprises means for fixing said pipette tip 101 'to said opening 18 to prevent leaks between the steps of the volume measurement. For example, as illustrated in fig. 7a and further describes, a plate 1c comprising holes of different sizes can be adapted to device 1.
    In variants, said means comprise a recognition system that can identify the shape and size of a liquid handling tip which approaches and includes an adaptation of the means modifying the shape of said opening 18. These adaptation means can include for example a spring, a shape memory alloy element or any system capable of modifying its shape and / or the size so that a liquid handling tip can be connected and maintained to the device 1 without leakage.
    In one embodiment, at least part of said chamber is made at least partially with MEMS technology.
    In variants, at least part of the device is made at least partially from glass, preferably using micro-structuring techniques for glass.
    In an advantageous embodiment, illustrated in FIGS. 7a, 7b, said device 1 is a monolithic device. A monolithic device may comprise a first part la comprising a through hole 18 and a second part Ib comprising said chambers 10,12. Fig. 7b shows by way of example, a section plane Y-Z AA'-BB 'of said first la and of the second part 2b which forms a single solid device. 1 Said first part 1a and second part 1b can be made with different materials. For example, the first part 1a can be made at least partially in glass while said second part is made at least partially in a silicon plate (Si), the chambers 10, 12 being produced, at least partially, by technologies of microstructuring.
    In one embodiment, said device 1 comprises a solid plate comprising it with various openings 18a, b, c. The solid plate can be adapted on said device which comprises means for sliding the plate 1 in a direction L so that, in different positions of said plate 1 relative to said device 1, different openings 18a, b, c can be aligned opposite said opening 18 of the device 1. Said openings can have any shape, for example a conical shape.
    CH 715 253 A2 In the embodiment of FIGS. 7a, 7b a valve 16 is illustrated diagrammatically and can be any valve, such as a manual valve, or a valve integrated in said chambers 10, 12 or the conduit 14.
    It is also understood that, in variants, several chambers located in different horizontal planes XZ can be arranged in fluid communication as described above. The chambers of the device 1 can have any shape and size and can be delimited by at least one curved surface, such as a cylindrical wall.
    The invention also relates to a volumetric displacement calibration system 2 comprising the volumetric displacement calibration device as described and comprising a computer performing the calculation of a displaced volume in accordance with the method of the invention. Fig. 7a illustrates an embodiment of a monolithic volumetric displacement calibration system 2 comprising the described monolithic device Ib and a part comprising it of electronic circuits, possibly also a microcomputer and / or microcontroller and electrical connectors for connecting the system 2 to other external electronic systems and / or a computer.
    In an advantageous embodiment, the device 1 and / or the system 2 comprises a computer or a printer configured for:
    - print an ISO calibration report on a printer. The printing is done on a self-adhesive label which can be placed directly on the pipette in order to follow the ISO calibration in a laboratory;
    - connect to a computer or tablet in order to connect to the laboratory's quality system;
    - connect to the Laboratory Information Management system (LIMS), an Electronic Laboratory Notebook system (ELN).
    It is also understood that in advantageous variants of the volumetric displacement calibration system 2, several devices 1 can be arranged so that a single system 2 can be used to calibrate, in series or in parallel, several manipulator devices liquids, such as pipettes. The system 2 can be adapted so that several types of liquid distribution the devices can be calibrated at the same time.
    Method for calibrating liquid handling devices [0062] The invention is also carried out by a method for calibrating liquid handling devices 100, such as liquid suction devices, preferably, but not exclusively, pipettes .
    The principle of the method is illustrated in the steps of FIGS. 4a-4f. The details of the method are now described for the preferred case of the use of a pipette 100. It is understood that the method of the invention can also be applied to other suction devices, such as those used in the automated suction devices. The suction device 100 is preferably a pipette which may be a pipette comprising a piston but not necessarily.
    In one embodiment, the method consists in measuring the pressure change Pi-P 0 caused by the displacement of the piston AV in the pipette. The appropriate opening of an additional reference volume V re f, allows the input volume V o and V to be calculated (equations 1 and 2). A valve 16 opens the reference chamber 10 (volume V re f), after the displacement AV and the pressure P 2 is recorded (fig. 4e).
    The pressures P o , Pi and P 2 allow, for example to said system 2, to calculate the effective displacement AV.
    The different volumes and pressures involved are detailed below:
    A) AV displacement in the volume V o (equation 1):
    Δ V = V Q - equation 1 B) Opening of the valve for the reference volume V re f (equation 2):
    V = - A V --—-- V ° ref equation 2 [G] Combination of equations 1 and 2:
    ^ V = V ref

    equation 3 More specifically, the method of the invention comprises the steps (ai) consisting in:
    CH 715 253 A2
    at)
    b)
    vs)
    d)
    e)
    g)
    h) providing a liquid handling system (100), preferably a pipette, configured to aspirate / dispense substances such as liquids;
    providing a liquid manipulator calibration device 1 comprising a first chamber 12 having a volume Vqo and a reference chamber 10, having a reference volume V re f, connected to said first chamber 12 by a first conduit 14 to which a first valve 16 is connected, said first valve 16 being configured to be switched from an open position, allowing said 12 first chamber and reference chamber 10 to be in fluid communication, to a closed position so that said first 12 and second chamber 10 are not in fluid communication, said first chamber 12 comprising a pressure sensor;
    connecting said pipette 100 to said first chamber 12 while said first valve 16 is in said open position;
    measuring an initial pressure P o in said first chamber by said pressure sensor;
    actuating the pipette 100 from a first volume reference position R1 to a second predetermined reference position R2 of positive or negative volume, said first and second reference positions R1, R2 defining a displaced volume AV;
    measuring an intermediate pressure Pf in said first chamber 12 using said pressure sensor while the pipette 100 remains in said second predetermined volume reference position R2;
    switching said first valve 16 from said closed position to said open position so that said first chamber 12 and said reference chamber 10 both reach a final pressure P 2 ;
    measuring said final pressure P 2 using said pressure sensor 20;
    determine the value of said displaced volume AV using the values of said initial, intermediate and final pressures Ρ Ί , P 2 by applying the relation of said equation 3:
    AV = Vref / (Pi / (Pi -Po) -P2 / (P2 -Pû)) The typical duration of the procedure is a few seconds for each step ai. The travel time must be the same as that which is systematically recommended for the use of the pipette with liquids, generally between 1 and 3 seconds. The pressure Pf is recorded approximately 1 second after the displacement AV in order to allow time for the atmospheric pressure to equilibrate. Immediately after reading Pi, the valve 16 connecting to the open reference cavity V re f θθί and the pressure P 2 is generally measured after 1 second.
    A pressure P 3 (fig. 4f) can be recorded after the piston has returned to its initial position. This does not add new information on the displacement volume but can be used to verify that no leakage or other malfunction has occurred during the measurement.
    The method of the invention is not limited to positive displacements but can be applied for negative displacements.
    The displaced volume V x caused by the opening of the valve to the reference volume (V re f) can be taken into account and compensated. In this case, formula 3 is modified and the volume of displacement AV is calculated by the following formula:
    In the embodiments illustrated in FIGS. 5a-5c, the device 1 and the system 2 can be constructed, as described above, with several reference volumes individually addressable for each case. Once a specific combination of chambers connected by fluid communication is selected, the measurement method remains similar to that described above.
    In one embodiment, rather than using several chambers, a single chamber can be used, the volume of which can be adapted. In such an embodiment, the method of the invention comprises the following steps:
    providing a liquid handling system 100, preferably a pipette comprising the piston 101 ', configured to aspirate / dispense substances such as liquids;
    providing a volumetric displacement calibration device 1 comprising at least one deformable chamber;
    CH 715 253 A2 c) connecting said liquid handling system 100 to said calibration device 1;
    d) modify the volume of said deformable chamber by a known volume change dV; e ') measure the pressure and deduce therefrom said volume V O o;
    f ') move the piston 101' so that a change in AV volume is determined g) compare the change in AV volume with the predetermined change in volume.
    In the embodiment of the invention in which the volumetric displacement calibration device 1 comprises at least one deformable chamber, the change in volume dV of the deformable chamber can be chosen to optimize the pressure changes. On the other hand, such a system requires a precise volume change dV and the system needs an internal actuator to determine V O o · The advantage is that only one chamber may be necessary, so it is not necessary to have a system comprising valves. In one embodiment, the method comprises before the steps of measuring the volume aj, another step of selecting the size of the tip of the pipette.
    In one embodiment, the method comprises the selection of a combination of chambers, in fluid communication, to form a first chamber 12 and / or a reference chamber 10.
    Leak test The invention also relates to the use of the volumetric displacement calibration device as described and specifically configured to measure the leak of a pipetting device.
    The invention also relates to the use of the displacement displacement calibration device as described and configured to measure the leakage of a pipette tip. It is understood that the measurements with the device and the method of the invention can be carried out with pipettes or other suction devices without a tip.
    The leak can be characterized by measuring the pressure in a closed chamber as a function of time. Leaks from the pipetting device and / or the connection of the nozzle can be characterized as illustrated in figs. 6a; 6b.
    The leak is measured after the displacement of the piston AV, by measuring the pressure Pi after two consecutive times separated partypically 1 or a few seconds. The leak rate can be precisely calculated in μΙ / s / mbar using the drift of P-, and the calculated value of the input volume.
    Certain products on the market include a leak tester which measures the leak rate of the pipettes. But as in these known devices, the input volume is not known, the value of the leak rate cannot be calculated with precision absolute values.
    Exemplary realization of the invention and experimental results [0084] Figs. 8 to 11 show typical measurement results (volumes are expressed in pi).
    Figs. 8 and 9 show the evolution of the pressure P-ι and P 2 for a displacement volume of the pipette in the ranges 100 μΙ (pipette P100) and 1000 μΙ (pipette P1000). This shows that the input volume for a P100 pipette must be lower to reach a pressure P-, and the pressure difference Ρ Ί -Ρ 2 sufficiently high compared to the resolution of the pressure sensor.
    FIG. 10, for example, illustrates the repeated measurements of a 200 μΙ pipette, for example for displacements of 200, 100 and 20 μΙ. The volume calibration error is as good as the ISO gravimetric calibration method.
    An important design parameter of the system is the value of the initial volume V o . The measurements with a pipette calibration system of the invention make it possible to calculate the ideal and preferred values of the volume V o .
    In an experimental configuration (Fig. 12) using a pipette calibration system according to the invention, it was determined that the initial volume V o was 1300 μΙ. Figs. 12-14 show the volume errors determined as a function of the value of V o . More precisely figs. 12-14 display the volume errors determined as a function of the volume displacements for different values of V o , that is to say 1300 μΙ and 800 μΙ. Fig. 2 shows that an initial volume Vo of 1300 μΙ leads to an error of approximately 0.2 μΙ but the error increases to a value of 0.3 μΙ for a displacement of 10 μΙ. The maximum pressure difference Ρ Ί -P o , deduced from the curve in fig. 12, is 81 mbar. Fig. 12 shows the effect of the input volume Vo on the random measurement error. The horizontal line at 0.3 μΙ is the limit of the ISO standard. With V o = 1300, the calibration of small displacements is at the limit of the standard. With 800 μΙ, the random error (calculated) is much lower and remains below the ISO limit, even for small displacements.
    The measurements made with a device 1 according to the invention show that a lower value of V o gives greater precision. An initial volume V o of 800 μΙ reduces the displacement measurement error from 10 μΙ to less than 0.2 μΙ, while maintaining an acceptable pressure value of approximately 139 mbar.
    CH 715 253 A2 In conclusion, it can be deduced that an initial volume V 0 must preferably be less than 5 times the volume displaced in order to maintain an acceptable pressure difference Δρ less than 200 mb.
    No simple and inexpensive prior art system can achieve the precision obtained with the device 1, the system 2 and the method of the invention.
    Applications Various applications of the process and of the volume calibration system are identified such as like and among others:
    1. A device for calibrating small fluid volume displacements based on precise pressure measurements.
    [2]
    2. A device for characterizing leaks in fluid displacement instruments based on the measurement of pressure variations as a function of time Pi (t).
    [3]
    3. A calibration of the dispensed volume and the leak rate of the laboratory pipettes.
    [4]
    4. In specific laboratory pipette applications, the device can be used to calibrate the pipette and measure leakage with or without a disposable tip mounted on the pipette.
    [5]
    5. The same device can be used for several ranges of pipette volume, such as, for example, 10, 20 μl, 100 μΙ, 1000 μΙ.
    [6]
    6. Depending on an appropriate design, the measurement range can be extended to more or less large volumes. Several ranges can be covered by adjusting the input volume.
    [7]
    7. Applications in which the input volume V o of the closed cavity including the volume in the pipette, the volume of the nozzle and the dead space of the device is not determined a priori.
    [8]
    8. applications in which the effect of the dead volume of the fluid switch V x must be determined and compensated.
    It is also understood that the volumetric displacement calibration device of the invention can be adapted to measure the volumes of other substances such as powders, gels or gases.
    Claims
    1. Method for calibrating a volumetric fluid handling system comprising the steps (a-i) consisting in:
    a) provide a suction system (100), preferably a pipette, configured to aspirate liquid or solid substances;
    b) providing a volumetric displacement calibration device (1) comprising a first chamber (12) having a volume V O o and a reference chamber (10) having a reference volume V re f, connected to said first chamber ( 12) by a first conduit (14) on which a first valve (16) is placed, said first valve (16) being configured to be switched from an open position, allowing said first chamber (12) and said chamber to reference (12) to be in fluid communication, towards a closed position so that said first chamber (12) and the second chamber (10) are not in fluid communication, said first chamber (12) comprising at least one sensor for pressure (20);
    c) connect said suction system (100) to said first chamber (12) while said first valve (14) is in said open position;
    d) measuring an initial pressure P o in said first chamber (12) with at least one pressure sensor (20);
    e) activating the suction system (100) from a first reference position R1 to a second predetermined positive or negative reference position R2, said first and second reference positions R1, R2 defining a displaced volume AV;
    f) measuring an intermediate pressure Pj in said first chamber by at least one pressure sensor while the suction system (100) remains in said second predetermined reference position R2;
    g) switching said first valve (14) from said closed position to said open position so that said first chamber (12) and said reference chamber (10) reach the same final pressure P 2 ;
    h) measuring said final pressure P 2 by at least one pressure sensor (20);
    I) determine the value of said displaced volume AV using the values of said initial, intermediate and final pressures Ρ Ί , P 2 , by applying the following relation:
    AV = V ref / (P 1 / (P 1 -P 0) -P 2 / (P 2 -P 0))
    CH 715 253 A2
    2. Method according to claim 1 comprising a step of connecting the first chamber (12) to at least a second predetermined chamber (17) by a second conduit (14) comprising a second valve (16), by positioning said second valve ( 16) in its open position.
    3. Method according to claim 1 or 2 comprising a step of connecting said reference chamber (16) to at least a second reference chamber (19) by another conduit (14) comprising another valve (16), by positioning said other valve (16) is in the open position.
    4. Method according to any one of claims 1 to 3, wherein said suction system (100) is a pipette, preferably comprising a pipette tip (100), and comprising, before the steps of measuring volume aj , an additional step of selecting a predetermined size of said pipette tip (100 ').
    5. Method according to any one of claims 1 to 4, in which said volumetric displacement calibration device (1) comprises a step of adapting the size and / or shape of the fluid communication of said suction system. (100) to said device (1) as a function of a predetermined size (w) of the suction opening (O) of said suction system (100).
    6. Method according to any one of claims 2 to 4 comprising fluid communication of a predetermined selection of chambers to form a first chamber (12) and / or fluid communication of another predetermined selection of chambers to form a chamber reference (10).
    7. Volumetric displacement calibration device (1) comprising at least one opening (18) configured to adapt a suction system, preferably a pipette, and in which
    - said volumetric displacement calibration device (1) comprises at least a first chamber (12) having a volume V oo and at least one reference chamber (12), having a volume V re f, connected to said first chamber ( 12) by a first conduit (14);
    - a first valve (16) located on said first conduit (14) and configured to be switchable from an open position, allowing said first chamber (12) and said reference chamber (10) to be in fluid communication, in a closed position in which said first chamber (12) and said reference chamber (10) are not in fluid communication;
    - at least one pressure sensor (20) connected to said first chamber (12).
    8. A volumetric displacement calibration device (1) according to claim 7 wherein said first chamber (12) comprises at least two chambers in fluid communication by a conduit (14 ', 14 ") comprising a valve (16', 16 "), Or in which the first chamber (12) has a variable volume.
    [9]
    9. A displacement displacement calibration device (1) according to claim 7 or claim 8, wherein said reference chamber (12) comprises at least two chambers in fluid communication by a conduit (14 ', 14) comprising a valve (16 ', 16), or wherein said reference chamber (12) has a variable volume.
    [10]
    10. A volumetric displacement calibration device according to any one of claims 7 to 9, in which said opening (18) is a configurable opening whose size and / or shape can be adapted according to a size and / or shape predetermined.
    [11]
    11. A device for calibrating the volumetric displacement according to any one of claims 7 to 10, in which at least one part is produced at least partially with MEMS technology and / or comprises at least one part in glass.
    [12]
    12. Volumetric displacement calibration device (1) according to any one of claims 7 to 11, wherein said device (1) is a monolithic device (1).
    [13]
    13. Volumetric displacement calibration device (1) according to any one of claims 7 to 11, in which the volume defined by the chamber of a suction system (100) and said first chamber (12) is less at 6 times the volume moved from the volumetric displacement calibration device (1) in operation.
    [14]
    14. Volumetric displacement calibration system (2) comprising the volumetric displacement calibration device (1) according to any one of claims 7 to 13 and comprising a computer performing the calculation of a displaced volume according to the method of claims 1 to 6.
    [15]
    15. Use of the displacement displacement calibration device (1) according to any one of claims 7 to 13, configured to measure the leakage of a suction system device (100).
    CH 715 253 A2


    CH 715 253 A2

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    同族专利:
    公开号 | 公开日
    EP3608640A1|2020-02-12|
    引用文献:
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    EP18188028.7A|EP3608640A1|2018-08-08|2018-08-08|Method of calibrating liquid handling devices and associated calibration apparatus|
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